Roy Robins-Browne

Multilocus sequence typing of Streptococcus pneumoniae by use of mass spectrometry

Publisher: American Society for Microbiology

Date: 11-2011

DOI: 10.1128/JCM.05113-11

Abstract: Multilocus sequence typing (MLST) is an important tool for the global surveillance of bacterial pathogens that is performed by comparing the sequences of designated housekeeping genes. We developed and tested a novel mass spectrometry-based method for MLST of Streptococcus pneumoniae . PCR licons were subjected to in vitro transcription and base-specific cleavage, followed by analysis of the resultant fragments by using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Comparison of the cleavage fragment peak patterns to a reference sequence set permitted automated identification of alleles. Validation experiments using 29 isolates of S. pneumoniae revealed that the results of MALDI-TOF MS MLST matched those obtained by traditional sequence-based MLST for 99% of alleles and that the MALDI-TOF MS method accurately identified two single-nucleotide variations. The MADLI-TOF MS method was then used for MLST analysis of 43 S. pneumoniae isolates from Papua New Guinean children. The majority of the isolates present in this population were not clonal and contained seven new alleles and 30 previously unreported sequence types.

Pneumococcal meningitis: Development of a new animal model

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 09-2006

DOI: 10.1097/01.MAO.0000231603.25961.F1

Can we prevent cochlear implant recipients from developing pneumococcal meningitis?

Publisher: Oxford University Press (OUP)

Date: 2008

DOI: 10.1086/524083

Abstract: The restoration of hearing to persons with severely or profoundly impaired hearing by means of a cochlear implant is one of the great achievements of bionics applied to medicine. However, pneumococcal meningitis in implant recipients has received high profile public attention as a result of the US Food and Drug Administration's public health notification and recent media attention. Worldwide, 118 of the 60,000 people who received cochlear implants over the past 20 years have acquired meningitis, causing deep concern in the international medical community. This review provides answers to pediatricians, internists, and infectious diseases doctors who have patients with cochlear implants and who have questions about the safety of the cochlear implant from both the clinical and scientific research perspectives. Both clinical and laboratory research support the notion that pneumococcal meningitis is more likely in patients who receive cochlear implantation, and that the surgical insertion technique and the cochlear implant design should be nontraumatic, and that all cochlear implant recipients should be offered vaccination against Streptococcus pneumoniae.

A novel mechanism of urease regulation in Yersinia enterocolitica

Publisher: Oxford University Press (OUP)

Date: 15-02-1997

DOI: 10.1016/S0378-1097(96)00528-9

Meningitis in children in Fiji: etiology, epidemiology, and neurological sequelae

Publisher: Elsevier BV

Date: 04-2012

DOI: 10.1016/J.IJID.2011.12.013

Abstract: To describe the etiology, epidemiology, neurological sequelae, and quality of life of children aged 1 month to less than 5 years admitted with meningitis to the Colonial War Memorial Hospital (CWMH), Suva, Fiji. Over a 3-year period, all eligible children with suspected meningitis admitted to CWMH had blood drawn for culture. Of these children, those for whom is was possible were tested for a four-fold rise in antibody titers to Haemophilus influenzae type b (Hib) and pneumococcal surface adhesin A (PsaA). Cerebrospinal fluid (CSF) was taken for bacteriological culture and antigen testing. CSF was also tested by PCR for Streptococcus species, Neisseria meningitidis, Hib, Mycobacterium tuberculosis, and enterovirus. Pneumococcal isolates were serotyped using multiplex-PCR reverse-line blot hybridization. Following discharge, cases underwent a neurological assessment, audiometry, and quality of life assessment (Pediatric Quality of Life Inventory (PedsQL) tool). There were 70 meningitis cases. Meningitis was more common in indigenous Fijian than Indo-Fijian children. Enterovirus was the most common etiological agent and appeared to be outbreak-associated. Streptococcus pneumoniae was the most common bacterial cause of meningitis with an annual incidence of 9.9 per 100 000 under 5 years old (95% confidence interval 4.9-17.7) and a case fatality rate of 36%. With the exception of deafness, neurological sequelae were more frequent in cases of bacterial meningitis than in viral meningitis (18.5% vs. 0%, p=0.04). Quality of life at follow-up was significantly lower in patients with bacterial meningitis than in those with viral meningitis (p=0.003) or meningitis of unknown etiology (p=0.004). During the study period an outbreak of enterovirus occurred making it the most common etiological agent identified. However in the absence of this outbreak, S. pneumoniae was the most common cause of childhood meningitis in Fiji. Bacterial meningitis is associated with serious sequelae and a reduced quality of life.

Technical Variability Is Greater than Biological Variability in a Microarray Experiment but Both Are Outweighed by Changes Induced by Stimulation

Publisher: Public Library of Science (PLoS)

Date: 31-05-2011

DOI: 10.1371/JOURNAL.PONE.0019556

Identification of a protein secretory pathway for the secretion of heat-labile enterotoxin by an enterotoxigenic strain of Escherichia coli

Publisher: Proceedings of the National Academy of Sciences

Date: 14-05-2002

DOI: 10.1073/PNAS.092152899

Abstract: Enterotoxigenic Escherichia coli (ETEC) is an enteric pathogen that causes cholera-like diarrhea in humans and animals. ETEC secretes a heat-labile enterotoxin (LT), which resembles cholera toxin, but the actual mechanism of LT secretion is presently unknown. We have identified a previously unrecognized type II protein secretion pathway in the prototypic human ETEC strain, H10407 (serotype O78:H11). The genes for this pathway are absent from E. coli K-12, although examination of the K-12 genome suggests that it probably once possessed them. The secretory pathway bears significant homology at the amino acid level to the type II protein secretory pathway required by Vibrio cholerae for the secretion of cholera toxin. With this in mind, we determined whether the homologous pathway of E. coli H10407 played a role in the secretion of LT. To this end, we inactivated the pathway by inserting a kanamycin-resistance gene into one of the genes ( gspD ) of the type II secretion pathway by homologous recombination. LT secretion by E. coli H10407 and the gspD mutant was assayed by enzyme immunoassay, and its biological activity was assessed by using Y-1 adrenal cells. This investigation showed that the protein secretory pathway is functional and necessary for the secretion of LT by ETEC. Our findings have revealed the mechanism for the secretion of LT by ETEC, which previously was unknown, and provide further evidence of close biological similarities of the LT and cholera toxin.

Threshold shift: Effects of cochlear implantation on the risk of pneumococcal meningitis

Publisher: Wiley

Date: 04-2007

DOI: 10.1016/J.OTOHNS.2006.11.039

Abstract: The study goals were to examine whether cochlear implantation increases the risk of meningitis in the absence of other risk factors and to understand the pathogenesis of pneumococcal meningitis post cochlear implantation. Four weeks following surgery, 54 rats (18 of which received a cochleostomy alone, 18 of which received a cochleostomy and acute cochlear implantation using standard surgical techniques, and 18 of which received a cochlear implant) were infected with Streptococcus pneumoniae via three different routes of bacterial inoculation (middle ear, inner ear, and intraperitoneal) to represent all potential routes of bacterial infection from the upper respiratory tract to the meninges. The presence of a cochlear implant reduced the threshold of bacteria required to cause pneumococcal meningitis from all routes of infection in healthy animals. The presence of a cochlear implant increases the risk of pneumococcal meningitis regardless of the route of bacterial infection. Early detection and treatment of pneumococcal infection such as otitis media may be required, as cochlear implantation may lead to a reduction of infectious threshold for meningitis.

Brachyspira aalborgi infection in four Australian children

Publisher: Wiley

Date: 08-2001

DOI: 10.1046/J.1440-1746.2001.T01-1-02543.X

Abstract: The clinical presentation of four children and adolescents (two males and two females with a mean age of 12.4 years range 9-16 years) with colorectal spirochetosis is discussed. Symptoms included persistent diarrhea (n = 2), rectal bleeding (n = 1) and abdominal pain (n = 2). In all patients, colorectal spirochetosis was an unanticipated finding on colonic histology, and the presence of spirochetes was confirmed by the use of electron microscopy. Spirochetes were identified as Brachyspira aalborgi by using PCR lification of the bacterial 16S rRNA and nicotinamide adenine dinucleotide oxidase sequences in all four patients. No other enteric pathogens were found. Although all patients appeared to respond to antibiotic treatment, the clinical significance of B. aalborgi as a human pathogen requires further investigation.

Protective effects of local administration of ciprofloxacin on the risk of pneumococcal meningitis after cochlear implantation

Publisher: Wiley

Date: 12-2006

DOI: 10.1097/01.MLG.0000243192.43574.81

Essential Role of the Type III Secretion System Effector NleB in Colonization of Mice by Citrobacter rodentium

Publisher: American Society for Microbiology

Date: 04-2006

DOI: 10.1128/IAI.74.4.2328-2337.2006

Abstract: Attaching and effacing (A/E) pathogens are a significant cause of gastrointestinal illness in humans and animals. All A/E pathogens carry a large pathogenicity island, termed the locus for enterocyte effacement (LEE), which encodes a type III secretion system that translocates several effector proteins into host cells. To identify novel virulence determinants in A/E pathogens, we performed a signature-tagged mutagenesis screen in C57BL/6 mice by using the mouse A/E pathogen Citrobacter rodentium . Five hundred seventy-six derivatives of C. rodentium were tested in pools of 12 mutants. One attenuated mutant carried a transposon insertion in nleB , which encodes a putative effector of the LEE-encoded type III secretion system (T3SS). nleB is present in a genomic pathogenicity island that also encodes another putative effector, NleE, immediately downstream. Using translational fusions with β-lactamase (TEM-1), we showed that both NleB and NleE were translocated into host cells by the LEE-encoded T3SS of enteropathogenic Escherichia coli . In addition, deletion of the gene encoding NleB in C. rodentium resulted in reduced colonization of mice in single infections and reduced colonic hyperplasia. In contrast, the deletion of other non-LEE-encoded effector genes in C. rodentium , nleC , nleD , or nleE , had no effect on host colonization or disease. These results suggest that nleB encodes an important virulence determinant of A/E pathogens.

Detection of a Widespread Clone of Pseudomonas aeruginosa in a Pediatric Cystic Fibrosis Clinic

Publisher: American Thoracic Society

Date: 10-2002

DOI: 10.1164/RCCM.200204-269OC

Phasevarion Mediated Epigenetic Gene Regulation in Helicobacter pylori

Publisher: Public Library of Science (PLoS)

Date: 19-12-2022

DOI: 10.1371/JOURNAL.PONE.0027569

Susceptibility to Acute Rheumatic Fever Based on Differential Expression of Genes Involved in Cytotoxicity, Chemotaxis, and Apoptosis

Publisher: American Society for Microbiology

Date: 02-2014

DOI: 10.1128/IAI.01152-13

Abstract: It is unknown why only some in iduals are susceptible to acute rheumatic fever (ARF). We investigated whether there are differences in the immune response, detectable by gene expression, between in iduals who are susceptible to ARF and those who are not. Peripheral blood mononuclear cells (PBMCs) from 15 ARF-susceptible and 10 nonsusceptible (control) adults were stimulated with rheumatogenic (Rh+) group A streptococci (GAS) or nonrheumatogenic (Rh−) GAS. RNA from stimulated PBMCs from each subject was cohybridized with RNA from unstimulated PBMCs on oligonucleotide arrays to compare gene expression. Thirty-four genes were significantly differentially expressed between ARF-susceptible and control groups after stimulation with Rh+ GAS. A total of 982 genes were differentially expressed between Rh+ GAS- and Rh− GAS-stimulated s les from ARF-susceptible in iduals. Thirteen genes were differentially expressed in the same direction (predominantly decreased) between the two study groups and between the two stimulation conditions, giving a strong indication of their involvement. Seven of these were immune response genes involved in cytotoxicity, chemotaxis, and apoptosis. There was variability in the degree of expression change between in iduals. The high proportion of differentially expressed apoptotic and immune response genes supports the current model of autoimmune and cytokine dysregulation in ARF. This study also raises the possibility that a “failed” immune response, involving decreased expression of cytotoxic and apoptotic genes, contributes to the immunopathogenesis of ARF.

Contribution of FliC to Epithelial Cell Invasion by Enterohemorrhagic Escherichia coli O113:H21

Publisher: American Society for Microbiology

Date: 02-2006

DOI: 10.1128/IAI.00435-06

Abstract: Enterohemorrhagic Escherichia coli (EHEC) O113:H21 can invade epithelial cells. In this study, we found that invasion but not adherence was inhibited by anti-FliC H21 specific antibodies. In addition, deletion of fliC H21 from EHEC O113:H21 resulted in an eightfold decrease in invasion that was restored upon transcomplementation with fliC H21 but not with fliC H6 . These results suggested that FliC plays an important role in the pathogenesis of infections caused by EHEC O113:H21 by allowing bacteria to penetrate the intestinal epithelium.

Characterization and evidence of mobilization of the LEE pathogenicity island of rabbit‐specific strains of enteropathogenic Escherichia coli

Publisher: Wiley

Date: 06-2002

DOI: 10.1046/J.1365-2958.2002.02968.X

Abstract: We have characterized the LEE pathogenicity islands (PAIs) of two rabbit-specific strains of enteropathogenic E. coli (REPEC), 83/39 (serotype O15:H-) and 84/110-1 (O103:H2), and have compared them to homologous loci from the human enteropathogenic and enterohaemorrhagic E. coli strains, E2348/69 and EDL933, and another REPEC strain, RDEC-1. All five PAIs contain a 34 kb core region that is highly conserved in gene order and nucleotide sequence. However, the LEE of 83/39 is significantly larger (59 540 basepairs) than those of the human strains, which are less than 44 kb, and has inserted into pheU tRNA. The regions flanking the 34 kb core of 83/39 contain homologues of two putative virulence determinants, efa1/lifA and senA. The LEE of 84/110-1 is approximately 85 kb and is located at pheV tRNA. Its core is almost identical to those of 83/39 and RDEC-1, apart from a larger espF gene, but its flanking regions contain trcA, a putative virulence determinant of EPEC. All three REPEC LEE PAIs contain a gene for an integrase, Int-phe. The LEE PAI of 84/110-1 is also flanked by short direct repeats (representing the 3'-end of pheV tRNA), suggesting that it may be unstable. To investigate this possibility, we constructed a LEE::sacB derivative of 84/110-1 and showed that the PAI was capable of spontaneous deletion. We also showed that Int-phe can mediate site-specific integration of foreign DNA at the pheU tRNA locus of E. coli DH1. Together these results indicate possible mechanisms of mobilization and integration of the LEE PAI.

The sigA Gene Which Is Borne on the she Pathogenicity Island of Shigella flexneri 2a Encodes an Exported Cy

Publisher: American Society for Microbiology

Date: 05-2000

DOI: 10.1128/IAI.68.5.2457-2463.2000

Abstract: In this study, the sigA gene situated on the she pathogenicity island of Shigella flexneri 2a was cloned and characterized. Sequence analysis showed that sigA encodes a 139.6-kDa protein which belongs to the SPATE (serine protease autotransporters of Enterobacteriaceae ) subfamily of autotransporter proteins. The demonstration that SigA is autonomously secreted from the cell to yield a 103-kDa processed form and possesses a conserved C-terminal domain for export from the cell were consistent with the autotransporter pathway of secretion. Functional analysis showed that SigA is a secreted temperature-regulated serine protease capable of degrading casein. SigA was cytopathic for HEp-2 cells, suggesting that it may be a cell-altering toxin with a role in the pathogenesis of Shigella infections. SigA was at least partly responsible for the ability of S. flexneri to stimulate fluid accumulation in ligated rabbit ileal loops.

Bicarbonate-Mediated Stimulation of RegA, the Global Virulence Regulator from Citrobacter rodentium

Publisher: Elsevier BV

Date: 12-2009

DOI: 10.1016/J.JMB.2009.10.033

Abstract: The global virulence regulatory protein RegA, an AraC-like regulator, controls the expression of more than 60 genes in the mouse enteric pathogen Citrobacter rodentium. In the presence of bicarbonate, RegA activates the transcription of a number of virulence determinants and inhibits the expression of a series of housekeeping genes. To elucidate the molecular mechanism by which bicarbonate stimulates RegA activity, we carried out biophysical and mutational analyses. Our data indicate that RegA exists as a dimer in solution regardless of bicarbonate concentration. A leucine zipper, located in the region downstream of the N-terminal domain, is responsible for dimerisation. The N-terminal arm itself is involved in modulating the response to bicarbonate, which appears to bind to a region comprising a series of beta-sheets within the N-terminal domain. The presence of bicarbonate relieves the autoinhibition of RegA activity by its N-terminal arm. RegA is the first ex le of a bacterial virulence regulator that utilises the light switch mechanism, previously described for the Escherichia coli AraC protein, to respond to a gut-associated effector that controls its activity.

Characterisation of atypical enteropathogenic E. coli strains of clinical origin

Publisher: Springer Science and Business Media LLC

Date: 03-06-2009

DOI: 10.1186/1471-2180-9-117

Abstract: Enteropathogenic E. coli (EPEC) is a prominent cause of diarrhoea, and is characterised in part by its carriage of a pathogenicity island: the locus for enterocyte effacement (LEE). EPEC is ided into two subtypes according to the presence of bundle-forming pili (BFP), a fimbrial adhesin that is a virulence determinant of typical EPEC (tEPEC), but is absent from atypical EPEC (aEPEC). Because aEPEC lack BFP, their virulence has been questioned, as they may represent LEE-positive Shiga toxin-producing E. coli (STEC) that have lost the toxin-encoding prophage, or tEPEC that have lost the genes for BFP. To determine if aEPEC isolated from humans in Australia or New Zealand fall into either of these categories, we undertook phylogenetic analysis of 75 aEPEC strains, and compared them with reference strains of EPEC and STEC. We also used PCR and DNA hybridisation to determine if aEPEC carry virulence determinants that could compensate for their lack of BFP. The results showed that aEPEC are highly heterogeneous. Multilocus sequence typing revealed that 61 of 75 aEPEC strains did not belong to known tEPEC or STEC clades, and of those that did, none expressed an O:H serotype that is frequent in tEPEC or STEC strains associated with disease. PCR for each of 18 known virulence-associated determinants of E. coli was positive in less than 15% of strains, apart from NleB which was detected in 30%. Type I fimbriae were expressed by all aEPEC strains, and 12 strains hybridised with DNA probes prepared from either bfpA or bfpB despite being negative in the PCR for bfpA . Our findings indicate that clinical isolates of aEPEC obtained from patients in Australia or New Zealand are not derived from tEPEC or STEC, and suggest that functional equivalents of BFP and possibly type I fimbriae may contribute to the virulence of some aEPEC strains.

A C-terminal class I PDZ binding motif of EspI/NleA modulates the virulence of attaching and effacing Escherichia coli and Citrobacter rodentium

Publisher: Hindawi Limited

Date: 02-11-2007

DOI: 10.1111/J.1462-5822.2007.01065.X

Abstract: Enteropathogenic Escherichia coli induces characteristic attaching-effacing (A/E) lesions on the intestinal mucosa during infection. The locus of enterocyte effacement is essential for A/E lesion formation and encodes a type III secretion system that translocates multiple effector proteins into the host cell. Following translocation, EspI/NleA localizes to the Golgi. Using the yeast two-hybrid system (Y2HS) and PSD-95/Disk-large/ZO-1 (PDZ)-domain protein array overlays, we identified 15 putative host-interacting partners of EspI. All but two of the target proteins contained PDZ domains. Examination of the EspI amino acid sequence revealed a C-terminal consensus class I PDZ binding motif. Deletion of the last 7 amino acids of EspI to generate EspI(DeltaC7) abrogated the Y2HS interaction between EspI and 5 of the 6 putative host cell target proteins tested. Deletion of the EspI PDZ binding motif also resulted in delayed trafficking of EspI to the Golgi. Using a mouse model of infection, we showed that Citrobacter rodentium expressing truncated EspI(DeltaC7) was attenuated when in competition with C. rodentium expressing full-length EspI. Overall, these results suggested that EspI may modulate the virulence of A/E pathogens by binding host PDZ-domain proteins.

The influence of bacille Calmette-Guérin vaccine strain on the immune response against tuberculosis: A randomized trial

Publisher: American Thoracic Society

Date: 15-01-2012

DOI: 10.1164/RCCM.201104-0714OC

Colonic Structural and Ion Transport Abnormalities in Suckling Rabbits Infected with Escherichia coli K12

Publisher: Ovid Technologies (Wolters Kluwer Health)

Date: 10-1997

DOI: 10.1097/00005176-199710000-00006

Abstract: Escherichia coli K12 is a laboratory strain considered nonpathogenic. The purpose of this study was to examine the effect of E. coli K12 infection on colonic structure and function. Suckling rabbits were infected at 10 days of age with 6 x 10(9) CFU E. coli by intragastric inoculation and were examined 4 to 5 days later. Segments of ileum and proximal and distal colon were removed for light and electron microscopy, and NaCl transport was examined in vitro under short-circuited conditions in Ussing chambers. Infection did not cause weight loss or diarrhea. Colonic mucosa was inflamed with infiltration by polymorphonuclear neutrophils mainly in the lamina propria. The proximal and distal colon exhibited reduced Na+ absorption. The proximal colon also showed increased Cl- secretion the ileum was unaffected. Infection with E. coli K12 disrupts the epithelium and alters ion transport in the colon, probably as a result of mucosal inflammation. The changes indicate that nonpathogenic E. coli have the potential to cause intestinal disease.

Nationwide study of haemolytic uraemic syndrome: clinical, microbiological, and epidemiological features

Publisher: BMJ

Date: 08-2001

DOI: 10.1136/ADC.85.2.125

Abstract: To establish the incidence and aetiology of haemolytic uraemic syndrome (HUS) in Australia and compare clinical and microbial characteristics of sporadic and outbreak cases. National active surveillance through the Australian Paediatric Surveillance Unit with monthly case notification from paediatricians, July 1994 to June 1998. Children under 15 years presenting with microangiopathic haemolytic anaemia, thrombocytopenia, and acute renal impairment were identified. Ninety eight cases were identified (incidence 0.64 per 10 5 children years/annum and 1.35 per 10 5 children years/annum). Eighty four were associated with diarrhoea (64 sporadic, 20 constituting an outbreak) and 14 were atypical. Shiga toxin producing Escherichia coli (STEC) O111:H− was the most common isolate in sporadic HUS and caused the outbreak. However O111:H− isolates from outbreak and sporadic cases differed in phage type and subtyping by DNA electrophoresis. STEC isolates from sporadic cases included O26:H−, O113:H21, O130:H11, OR:H9, O157:H−, ONT:H7, and ONT:H−. STEC O157:H7 was not isolated from any case. Only O111:H− isolates produced both Shiga toxins 1 and 2 and possessed genes encoding E coli attaching and effacing gene (intimin) and enterohemolysin. Outbreak cases had worse gastrointestinal and renal disease at presentation and more extrarenal complications. Linking national surveillance with a specialised laboratory service allowed estimation of HUS incidence and provided information on its aetiology. In contrast to North America, Japan, and the British Isles, STEC O157:H7 is rare in Australia however, non-O157:H7 STEC cause severe disease including outbreaks. Disease severity in outbreak cases may relate to yet unidentified virulence factors of the O111:H− strain isolated.

Efficacy of antimicrobial polymer coatings in an animal model of bacterial infection associated with foreign body implants

Publisher: Oxford University Press (OUP)

Date: 16-03-2010

DOI: 10.1093/JAC/DKQ057

Abstract: To assess support discs, comprising polyethylene terephthalate (PET), coated with different polymer/levofloxacin combinations for antimicrobial activity in an animal model of infection, in order to explore the use of specific polymer coatings incorporating levofloxacin as a means of reducing device-related infections. Aliphatic polyester-polyurethanes containing different ratios of poly(lactic acid) diol and poly(caprolactone) diol were prepared, blended with levofloxacin and then used to coat support discs. The in vitro levofloxacin release profiles from these discs were measured in aqueous solution. Mice were surgically implanted with the coated discs placed subcutaneously and infection was initiated by injection of 10(6) cfu of Staphylococcus aureus into the subcutaneous pocket containing the implant. After 5, 10, 20 and 30 days, the discs were removed, and the number of bacteria adhering to the implant and the residual antimicrobial activity of the discs were determined. In vitro, the release of levofloxacin from the coated discs occurred at a constant rate and then reached a plateau at different timepoints, depending on the polymer preparation used. In vivo, none of the discs coated with polymer blends containing levofloxacin was colonized by S. aureus, whereas 94% of the discs coated with polymer alone were infected. All discs coated with levofloxacin-blended polymers displayed residual antimicrobial activity for at least 20 days post-implantation. Bioerodable polyester-polyurethane polymer coatings containing levofloxacin can prevent bacterial colonization of implants in an intra-operative model of device-related infections.

Simulation of non-Newtonian molten polymer on natural convection in a sinusoidal heated cavity using FDLBM

Publisher: Elsevier BV

Date: 07-2014

DOI: 10.1016/J.MOLLIQ.2014.02.031

RegR virulence regulon of rabbit-specific enteropathogenic Escherichia coli strain E22.

Publisher: American Society for Microbiology

Date: 04-2013

DOI: 10.1128/IAI.01325-12

Abstract: AraC-like regulators play a key role in the expression of virulence factors in enteric pathogens, such as enteropathogenic Escherichia coli (EPEC), enterotoxigenic E. coli , enteroaggregative E. coli , and Citrobacter rodentium . Bioinformatic analysis of the genome of rabbit-specific EPEC (REPEC) strain E22 (O103:H2) revealed the presence of a gene encoding an AraC-like regulatory protein, RegR, which shares 71% identity to the global virulence regulator, RegA, of C. rodentium . Microarray analysis demonstrated that RegR exerts 25- to 400-fold activation on transcription of several genes encoding putative virulence-associated factors, including a fimbrial operon (SEF14), a serine protease, and an autotransporter adhesin. These observations were confirmed by proteomic analysis of secreted and heat-extracted surface-associated proteins. The mechanism of RegR-mediated activation was investigated by using its most highly upregulated gene target, sefA . Transcriptional analyses and electrophoretic mobility shift assays showed that RegR activates the expression of sefA by binding to a region upstream of the sefA promoter, thereby relieving gene silencing by the global regulatory protein H-NS. Moreover, RegR was found to contribute significantly to virulence in a rabbit infection experiment. Taken together, our findings indicate that RegR controls the expression of a series of accessory adhesins that significantly enhance the virulence of REPEC strain E22.

Effect of Pneumococcal Vaccination on Nasopharyngeal Carriage of Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, and Staphylococcus aureus in Fijian Children

Publisher: American Society for Microbiology

Date: 03-2012

DOI: 10.1128/JCM.06589-11

Abstract: The 7-valent pneumococcal conjugate vaccine (PCV7) reduces carriage of vaccine type Streptococcus pneumoniae but leads to replacement by nonvaccine serotypes and may affect carriage of other respiratory pathogens. We investigated nasopharyngeal carriage of S. pneumoniae , Haemophilus influenzae , Moraxella catarrhalis , and Staphylococcus aureus in Fijian infants participating in a pneumococcal vaccine trial using quantitative PCR. Vaccination did not affect pathogen carriage rates or densities, whereas significant differences between the two major ethnic groups were observed.

Evolution of multidrug resistance during staphylococcus aureus infection involves mutation of the essential two component regulator WalKR

Publisher: Public Library of Science (PLoS)

Date: 10-11-2011

DOI: 10.1371/JOURNAL.PPAT.1002359

Superantigen genes in group A streptococcal isolates and their relationship with emm types

Publisher: Microbiology Society

Date: 10-2008

DOI: 10.1099/JMM.0.2008/001156-0

Abstract: Superantigens are important virulence factors in the pathogenesis of invasive disease caused by group A streptococcus (GAS). There has been a recent re-emergence of this disease worldwide. A number of novel superantigens have been described recently. This study investigated 107 isolates of GAS for possession of each of the 11 currently known superantigen genes to determine the prevalence, co-occurrence and genetic restriction amongst different emm types of GAS. The results were compared with those in previously published studies. Superantigen genes were not randomly distributed amongst GAS isolates. Certain combinations of superantigen genes were more common and the majority of emm types showed restricted superantigen profiles. This is the first prevalence study of GAS isolates to include the complete range of known superantigen genes and their restriction amongst emm types. This study contributes to the understanding of the relationship between superantigen genes and emm types, and highlights the importance of comprehensive studies in different populations.

Bicarbonate-mediated transcriptional activation of divergent operons by the virulence regulatory protein, RegA, from Citrobacter rodentium

Publisher: Wiley

Date: 23-03-2008

DOI: 10.1111/J.1365-2958.2008.06171.X

Abstract: Regulation of virulence gene expression plays a central role in the pathogenesis of enteric bacteria as they encounter erse environmental conditions in the gastrointestinal tract of their hosts. In this study, we investigated environmental regulation of two putative virulence determinants adcA and kfc by RegA, an AraC/XylS-like regulator, from Citrobacter rodentium, and identified bicarbonate as the environmental signal which induced transcription of adcA and kfc through RegA. Primer extension experiments showed that adcA and kfc were ergently transcribed from sigma(70) promoters. In vivo and in vitro experiments demonstrated that bicarbonate facilitated and stabilized the binding of RegA to an operator located between the two promoters. The interaction of RegA with its DNA target resulted in the formation of a nucleosome-like structure, which evidently displaced the histone-like proteins, H-NS and StpA, from the adcA and kfc promoter regions, leading to transcriptional derepression. In addition, our results indicated that RegA also behaved as a Class I activator by directly stimulating transcription initiation by RNA polymerase. This is the first report to describe the molecular mechanism by which an environmental chemical stimulates transcription of virulence-associated genes of an enteric pathogen through an AraC/XlyS-like activator.

Escherichia coli as a cause of diarrhea

Publisher: Wiley

Date: 04-2002

DOI: 10.1046/J.1440-1746.2002.02769.X

Abstract: Escherichia coli is the best-known member of the normal microbiota of the human intestine and a versatile gastrointestinal pathogen. The varieties of E. coli that cause diarrhea are classified into named pathotypes, including enterotoxigenic, enteroinvasive, enteropathogenic and enterohemorrhagic E. coli. In idual strains of each pathotype possess a distinct set of virulence-associated characteristics that determine the clinical, pathological and epidemiological features of the diseases they cause. In the present brief review, we summarize the key distinguishing features of the major pathotypes of diarrheagenic E. coli. Knowledge of the pathogenic mechanisms of these bacteria has led to the development of rational interventions for the treatment and prevention of E. coli-induced diarrhea. In addition, investigations into E. coli virulence are providing useful insights into the origins and evolution of bacterial pathogens more generally.

A comparative analysis of polyfunctional t cells and secreted cytokines induced by bacille calmette-guérin immunisation in children and adults

Publisher: Public Library of Science (PLoS)

Date: 19-07-2012

DOI: 10.1371/JOURNAL.PONE.0037535

Immune Response to Infection withMycobacterium ulcerans

Publisher: American Society for Microbiology

Date: 03-2001

DOI: 10.1128/IAI.69.3.1704-1707.2001

Abstract: Mycobacterium ulcerans is a slow-growing, acid-fast bacillus that causes chronic necrotizing skin ulcers known as Buruli ulcers. Previously reported information on immunity to this mycobacterium is limited. We examined immune responses to M. ulcerans and M. bovis BCG in patients with M. ulcerans disease and in 20 healthy control subjects (10 tuberculin test positive and 10 tuberculin test negative). Cell-mediated immunity was assessed by stimulating peripheral blood mononuclear cells (PBMC) with whole mycobacteria and then measuring PBMC proliferation and the production of gamma interferon (IFN-γ). Humoral immunity was assessed by immunoblotting. PBMC from all subjects showed significantly greater proliferation and IFN-γ production in response to stimulation with living mycobacteria compared with killed cells. However, PBMC from subjects with past or current M. ulcerans disease showed significantly reduced proliferation and production of IFN-γ in response to stimulation with live M. ulcerans or M. bovis than PBMC from healthy, tuberculin test-positive subjects ( P 0.001) and showed results in these assays comparable to those of tuberculin test-negative subjects ( P 0.2). Serum from 9 of 11 patients with M. ulcerans disease, but no control subject, contained antibodies to M. ulcerans . The results indicate that patients with M. ulcerans infection mount an immune response to M. ulcerans as evidenced by antibody production, but they demonstrate profound systemic T-cell anergy to mycobacterial antigens. These findings may explain some of the distinct clinical and pathological features of M. ulcerans -induced disease.

Hemolytic Uremic Syndrome

Publisher: Elsevier BV

Date: 09-2005

DOI: 10.1016/J.CPPEDS.2005.06.002

The H-NS protein represses transcription of the eltAB operon, which encodes heat-labile enterotoxin in enterotoxigenic Escherichia coli, by binding to regions downstream of the promoter

Publisher: Microbiology Society

Date: 04-2005

DOI: 10.1099/MIC.0.27734-0

Abstract: Heat-labile enterotoxin, a major virulence determinant of enterotoxigenic Escherichia coli, is encoded by the eltAB operon. To elucidate the molecular mechanism by which the heat-stable nucleoid-structural (H-NS) protein controls transcription of eltAB, the authors constructed an eltAB-lacZ transcriptional fusion and performed beta-galactosidase analysis. The results showed that H-NS protein exerts fivefold repression on transcription from the eltAB promoter at 37 degrees C and 10-fold repression at 22 degrees C. Two silencer regions that were required for H-NS-mediated repression of eltAB expression were identified, both of which were located downstream of the start site of transcription. One silencer was located between +31 and +110, the other between +460 and +556, relative to the start site of transcription, and they worked cooperatively in repression. DNA sequences containing the silencers were predicted to be curved by in silico analysis and bound H-NS protein directly in vitro. Repression of eltAB transcription by H-NS was independent of promoter strength, and the presence of H-NS protein did not affect promoter opening in vitro, indicating that repression was achieved by inhibiting promoter clearance or blocking transcription elongation, probably via DNA looping between the two silencers.

Identification of a Novel Fimbrial Gene Cluster Related to Long Polar Fimbriae in Locus of Enterocyte Effacement-Negative Strains of Enterohemorrhagic Escherichia coli

Publisher: American Society for Microbiology

Date: 12-2002

DOI: 10.1128/IAI.70.12.6761-6769.2002

Abstract: Enterohemorrhagic Escherichia coli (EHEC) is a food-borne cause of bloody diarrhea and the hemolytic-uremic syndrome (HUS) in humans. Most strains of EHEC belong to a group of bacterial pathogens that cause distinctive lesions on the host intestine termed attaching-and-effacing (A/E) lesions. A/E strains of EHEC, including the predominant serotype, O157:H7, are responsible for the majority of HUS outbreaks worldwide. However, several serotypes of EHEC are not A/E pathogens because they lack the locus of enterocyte effacement (LEE) pathogenicity island. Nevertheless, such strains have been associated with sporadic cases and small outbreaks of hemorrhagic colitis and HUS. Of these LEE-negative organisms, O113:H21 is one of the most commonly isolated EHEC serotypes in many regions. Clinical isolates of LEE-negative EHEC typically express Shiga toxin 2 and carry an ∼90-kb plasmid that encodes EHEC hemolysin, but in the absence of LEE, little is known about the way in which these pathogens colonize the host intestine. In this study we describe the identification of a novel fimbrial gene cluster related to long polar fimbriae in EHEC O113:H21. This chromosomal region comprises four open reading frames, lpfA to lfpD , and has the same location in the EHEC O113:H21 genome as O island 154 in the prototype EHEC O157:H7 strain, EDL933. In a survey of EHEC of other serotypes, homologues of lpfA O113 were found in 26 of 28 LEE-negative and 8 of 11 non-O157:H7 LEE-positive EHEC strains. Deletion of the putative major fimbrial subunit gene, lpfA , from EHEC O113:H21 resulted in decreased adherence of this strain to epithelial cells, suggesting that lpf O113 may function as an adhesin in LEE-negative isolates of EHEC.

Influence of BCG vaccine strain on the immune response and protection against tuberculosis

Publisher: Oxford University Press (OUP)

Date: 08-2008

DOI: 10.1111/J.1574-6976.2008.00118.X

Abstract: The Bacille Calmette-Guérin (BCG) vaccine has been used for more than 80 years to protect against tuberculosis. Worldwide, over 90% of children are immunized with BCG, making it the most commonly administered vaccine, with more than 120 million doses used each year. Although new tuberculosis vaccines are under investigation, BCG will remain the cornerstone of the strategy to fight the worsening tuberculosis pandemic for the foreseeable future. The recent delineation of genetic differences between BCG vaccine strains has renewed interest in the influence of the vaccine strain on the protective efficacy against tuberculosis. This review critically examines the data from animal and human studies comparing BCG vaccine strains. Although there is good evidence to support the notion that the induced immune response and protection afforded against tuberculosis differs between BCG vaccine strains, currently, there are insufficient data to favour or recommend one particular strain. Identifying BCG strains with superior protection would have a dramatic effect on tuberculosis control at a population level: a small increment in protection provided by BCG immunization will prevent large numbers of cases of severe tuberculosis and deaths, particularly in children.

The type III effectors NleE and NleB from enteropathogenic E. coli and OspZ from Shigella block nuclear translocation of NF-kappaB p65

Publisher: Public Library of Science (PLoS)

Date: 13-05-2010

DOI: 10.1371/JOURNAL.PPAT.1000898

Lactobacillus GG treatment during pregnancy for the prevention of eczema: a randomized controlled trial

Publisher: Wiley

Date: 12-2010

DOI: 10.1111/J.1398-9995.2010.02507.X

Abstract: Probiotic supplementation in early life may be effective for preventing eczema. Previous studies have suggested that prenatal administration may be particularly important for beneficial effects. We examined whether prenatal treatment with the probiotic Lactobacillus rhamnosus GG (LGG) can influence the risk of eczema during infancy. We recruited 250 pregnant women carrying infants at high risk of allergic disease to a randomized controlled trial of probiotic supplementation (LGG 1.8 × 10(10) cfu/day) from 36 weeks gestation until delivery. Infants were assessed during their first year for eczema or allergic sensitization. Immunological investigations were performed in a subgroup. Umbilical cord blood was examined for dendritic cell and regulatory T cell numbers and production of TGFβ, IL-10, IL-12, IL-13, IFN-γ and TNFα. Maternal breast milk was examined for total IgA, soluble CD14 and TGFβ. Prenatal probiotic treatment was not associated with reduced risk of eczema (34% probiotic, 39% placebo RR 0.88 95% CI 0.63, 1.22) or IgE-associated eczema (18% probiotic, 19% placebo RR 0.94 95% CI 0.53, 1.68). Prenatal probiotic treatment was not associated with any change in cord blood immune markers, but was associated with decreased breast milk soluble CD14 and IgA levels. Prenatal treatment with Lactobacillus rhamnosus GG was not sufficient for preventing eczema. If probiotics are effective for preventing eczema, then a postnatal component to treatment or possibly an alternative probiotic strain is necessary.

A Modular Approach to Assembly of Totally Synthetic Self-adjuvanting Lipopeptide-based Vaccines Allows Conformational Epitope Building

Publisher: Elsevier BV

Date: 04-2011

DOI: 10.1074/JBC.M111.227744

Discovery of an archetypal protein transport system in bacterial outer membranes

Publisher: Springer Science and Business Media LLC

Date: 04-2012

DOI: 10.1038/NSMB.2261

Abstract: Bacteria have mechanisms to export proteins for erse purposes, including colonization of hosts and pathogenesis. A small number of archetypal bacterial secretion machines have been found in several groups of bacteria and mediate a fundamentally distinct secretion process. Perhaps erroneously, proteins called 'autotransporters' have long been thought to be one of these protein secretion systems. Mounting evidence suggests that autotransporters might be substrates to be secreted, not an autonomous transporter system. We have discovered a new translocation and assembly module (TAM) that promotes efficient secretion of autotransporters in proteobacteria. Functional analysis of the TAM in Citrobacter rodentium, Salmonella enterica and Escherichia coli showed that it consists of an Omp85-family protein, TamA, in the outer membrane and TamB in the inner membrane of erse bacterial species. The discovery of the TAM provides a new target for the development of therapies to inhibit colonization by bacterial pathogens.

Rabbit-specific fimbriae, Ral, alter the patterns of in vitro adherence and intestinal colonisation of rabbits by human-specific enteropathogenic E. coli

Publisher: Elsevier BV

Date: 07-2009

DOI: 10.1016/J.MICINF.2009.04.023

Abstract: Enteropathogenic Escherichia coli (EPEC) poses a significant threat to human health, causing diarrhoea in children worldwide, and is a leading cause of infant mortality in developing countries. The pathogenic effects of EPEC and other attaching-effacing (A/E) bacteria result from adhesion to the intestinal mucosa by a variety of mechanisms, including fimbrial adhesins, which are believed to contribute to the host and tissue specificity of EPEC by their interaction with specific receptors on cell surfaces. In this study we investigated the contribution of a fimbrial adhesin, Ral, of rabbit-specific EPEC (REPEC) to host specificity by introducing Ral into derivatives of human-specific EPEC (hEPEC) strain, E2348/69, in which expression of the fimbrial adhesin, Bfp, had been interrupted. Although unable to cause diarrhoeal disease in rabbits, Ral-bearing hEPEC strains colonised rabbit intestine more efficiently and showed altered intestinal localisation when compared to an isogenic Ral-negative strain. These findings suggest that Ral enhances the initial interaction between a DeltabfpA mutant of hEPEC and rabbit intestine and may influence tissue specificity, but is not sufficient on its own to transform hEPEC into a rabbit pathogen. This study affords new insights into the complex mechanisms which determine the host range of bacterial pathogens.

Contribution of Secretory Antibodies to Intestinal Mucosal Immunity against Helicobacter pylori

Publisher: American Society for Microbiology

Date: 10-2013

DOI: 10.1128/IAI.01424-12

Abstract: The natural immune response to Helicobacter pylori neither clears infection nor prevents reinfection. However, the ability of secretory antibodies to influence the course of H. pylori infection has not been determined. We compared the natural progression of H. pylori infection in wild-type C57BL/6 mice with that in mice lacking the polymeric immunoglobulin receptor (pIgR) that is essential for the secretion of polymeric antibody across mucosal surfaces. H. pylori SS1-infected wild-type and pIgR knockout (KO) mice were s led longitudinally for gastrointestinal bacterial load, antibody response, and histological changes. The gastric bacterial loads of wild-type and pIgR KO mice remained constant and comparable at up to 3 months postinfection (mpi) despite SS1-reactive secretory IgA in the intestinal contents of wild-type mice at that time. Conversely, abundant duodenal colonization of pIgR KO animals contrasted with the near-total eradication of H. pylori from the intestine of wild-type animals by 3 mpi. H. pylori was cultured only from the duodenum of those animals in which colonization in the distal gastric antrum was of sufficient density for immunohistological detection. By 6 mpi, the gastric load of H. pylori in wild-type mice was significantly lower than in pIgR KO animals. While there was no corresponding difference between the two mouse strains in gastric pathology results at 6 mpi, reductions in gastric bacterial load correlated with increased gastric inflammation together with an intestinal secretory antibody response in wild-type mice. Together, these results suggest that naturally produced secretory antibodies can modulate the progress of H. pylori infection, particularly in the duodenum.

Virulence regulation in Citrobacter rodentium: the art of timing

Publisher: Wiley

Date: 20-04-2010

DOI: 10.1111/J.1751-7915.2009.00114.X

Disarming Bacterial Virulence through Chemical Inhibition of the DNA Binding Domain of an AraC-like Transcriptional Activator Protein

Publisher: Elsevier BV

Date: 10-2013

DOI: 10.1074/JBC.M113.503912

Effect of bacterial invasion of macrophages on the outcome of assays to assess bacterium–macrophage interactions

Publisher: Elsevier BV

Date: 06-1998

DOI: 10.1016/S0022-1759(98)00053-2

Abstract: In vitro assays to quantify killing of bacteria by macrophages provide useful insights into host-pathogen relations. In the present study, we used strains of Yersinia enterocolitica and Escherichia coli which varied in their ability to invade mammalian cells to evaluate these assays. The results showed that 30 min and 24 h after incubation with murine bone marrow-derived macrophages, strains of Y. enterocolitica and E. coli which expressed invasin (an outer membrane protein which allows bacteria to penetrate mammalian cells) achieved significantly greater numbers in macrophages than otherwise isogenic bacteria which lacked this protein (P 0.2). This study has shown (1) that invasin-mediated penetration of macrophages by bacteria is not associated with enhanced intracellular survival, and (2) that invasion of macrophages by bacteria may influence the interpretation of assays for bactericidal capacity unless allowance is made for the number of bacteria ingested during the early phase of the assay.

Assessment of the protective effect of pneumococcal vaccination in preventing meningitis after cochlear implantation

Publisher: American Medical Association (AMA)

Date: 10-2007

DOI: 10.1001/ARCHOTOL.133.10.987

Abstract: To examine if a 23-valent pneumococcal capsular polysaccharide vaccine (PPV23) reduces the risk of meningitis in healthy rats after cochlear implantation. Interventional animal study. Thirty-six rats (18 immunized and 18 unimmunized) received cochlear implantations and were then infected with Streptococcus pneumoniae via 3 different routes (hematogenous, middle ear, and inner ear) in numbers sufficient to induce meningitis. The rats with implants that received PPV23 were protected from meningitis when the bacteria were delivered via the hematogenous and middle-ear routes (Fisher exact test P<.05). However, the protective effect of the vaccine in the rats with implants was only moderate when the bacteria were inoculated directly into the inner ear. Our animal model clearly demonstrates that immunization can protect healthy rats with a cochlear implant from meningitis caused by a vaccine-covered serotype. This finding supports the notion that all current and future implant recipients should be vaccinated against S pneumoniae.

Reply: Bacille calmette-guérin vaccine: Innate immunity and nonspecific effects

Publisher: American Thoracic Society

Date: 04-2013

DOI: 10.1164/AJRCCM.187.7.779

Transcriptional Activation of the mrkA Promoter of the Klebsiella pneumoniae Type 3 Fimbrial Operon by the c-di-GMP-Dependent MrkH Protein

Publisher: Public Library of Science (PLoS)

Date: 14-11-2013

DOI: 10.1371/JOURNAL.PONE.0079038

RegA, an AraC-like protein, is a global transcriptional regulator that controls virulence gene expression in Citrobacter rodentium

Publisher: American Society for Microbiology

Date: 11-2008

DOI: 10.1128/IAI.00770-08

Abstract: Citrobacter rodentium is an attaching and effacing pathogen which causes transmissible colonic hyperplasia in mice. Infection with C. rodentium serves as a model for infection of humans with enteropathogenic and enterohemorrhagic Escherichia coli . To identify novel colonization factors of C. rodentium , we screened a signature-tagged mutant library of C. rodentium in mice. One noncolonizing mutant had a single transposon insertion in an open reading frame (ORF) which we designated regA because of its homology to genes encoding members of the AraC family of transcriptional regulators. Deletion of regA in C. rodentium resulted in markedly reduced colonization of the mouse intestine. Examination of lacZ transcriptional fusions using promoter regions of known and putative virulence-associated genes of C. rodentium revealed that RegA strongly stimulated transcription of two newly identified genes located close to regA , which we designated adcA and kfcC . The cloned adcA gene conferred autoaggregation and adherence to mammalian cells to E. coli strain DH5α, and a kfc mutation led to a reduction in the duration of intestinal colonization, but the kfc mutant was far less attenuated than the regA mutant. These results indicated that other genes of C. rodentium whose expression required activation by RegA were required for colonization. Microarray analysis revealed a number of RegA-regulated ORFs encoding proteins homologous to known colonization factors. Transcription of these putative virulence determinants was activated by RegA only in the presence of sodium bicarbonate. Taken together, these results show that RegA is a global regulator of virulence in C. rodentium which activates factors that are required for intestinal colonization.

In silico serotyping of E. coli from short read data identifies limited novel O-loci but extensive diversity of O:H serotype combinations within and between pathogenic lineages

Publisher: Microbiology Society

Date: 11-07-2016

DOI: 10.1099/MGEN.0.000064

Contribution of Efa1/LifA to the adherence of enteropathogenic Escherichia coli to epithelial cells

Publisher: Elsevier BV

Date: 05-2003

DOI: 10.1016/S0882-4010(03)00026-3

Abstract: Enteropathogenic E. coli(EPEC) is an important diarrhoeal pathogen that induces characteristic lesions on the host intestine termed attaching and effacing (A/E) lesions. In this study we have examined the contribution of a large gene, efa1, which is present in all A/E pathogens, to the adherence phenotype of EPEC. An efa- derivative of EPEC JPN15 was constructed and this mutant was significantly less adherent to epithelial cells than the parent strain. The JPN15 efa- derivative was FAS-positive, produced EspA filaments and showed comparable levels of EspA secretion to JPN15. In addition, polyclonal antibodies raised to Efa1 partially inhibited the adherence of JPN15 to cultured epithelial cells. In further work, we showed that human and rabbit hosts infected with an A/E pathogen produced antibodies to Efa1 and we observed that the truncated form of efa1 present in EHEC O157:H7 was specific to that serotype. Generally efa1 was present in its entirety in the genomes of other A/E pathogens. Overall our data suggest that Efa1 has host cell binding activity, at least in tissue culture, and that it is produced during infection. These findings suggest that Efa1 may play a direct role in the pathogenesis of infections caused by A/E pathogens.

Burden and aetiology of diarrhoeal disease in infants and young children in developing countries (the Global Enteric Multicenter Study, GEMS): a prospective, case-control study.

Publisher: Elsevier BV

Date: 07-2013

DOI: 10.1016/S0140-6736(13)60844-2

Identification of a novel genetic locus that is required for in vitro adhesion of a clinical isolate of enterohaemorrhagic Escherichia coli to epithelial cells

Publisher: Wiley

Date: 2000

DOI: 10.1046/J.1365-2958.2000.01690.X

Abstract: Enterohaemorrhagic Escherichia coli (EHEC) are food-borne intestinal pathogens with a low infectious dose. Adhesion of some EHEC strains to epithelial cells is attributed, in part, to intimin, but other factors may be required for the intestinal colonizing ability of these bacteria. In order to identify additional adherence factors of EHEC, we generated transposon mutants of a clinical EHEC isolate of serotype O111:H-, which displayed high levels of adherence to cultured Chinese hamster ovary (CHO) cells. One mutant was markedly deficient in CHO cell adherence, human red blood cell agglutination and autoaggregation. Sequence analysis of the gene disrupted in this mutant revealed a 9669 bp novel chromosomal open reading frame (ORF), which was designated efa1, for EHEC factor for adherence. efa1 displayed 28% amino acid identity with the predicted product of a recently described ORF from the haemolysin-encoding plasmid of EHEC O157:H7. The amino termini of the putative products of these two genes exhibit up to 38% amino acid similarity to Clostridium difficile toxins A and B. efa1 occurred within a novel genetic locus, at least 15 kb in length, which featured a low G+C content, several insertion sequence homologues and a homologue of the Shigella flexneri enterotoxin ShET2. DNA probes prepared from different regions of efa1 hybridized with all of 116 strains of attaching-effacing E. coli (AEEC) of a variety of serotypes, including enteropathogenic E. coli (EPEC) and EHEC, but with none of 91 non-AEEC strains. Nevertheless, efa1 was not required for the attachment-effacement phenotype, and the efa1 locus was not physically linked to the locus for enterocyte effacement (LEE) pathogenicity island, which is responsible for this phenotype in EPEC. These findings suggest that efa1 encodes a novel virulence-associated determinant of AEEC, which contributes to the adhesive capacity of these bacteria.

Influence of gastric acid on susceptibility to infection with ingested bacterial pathogens

Publisher: American Society for Microbiology

Date: 02-2008

DOI: 10.1128/IAI.01138-07

Abstract: Despite the widely held belief that gastric acid serves as a barrier to bacterial pathogens, there are almost no experimental data to support this hypothesis. We have developed a mouse model to quantify the effectiveness of gastric acid in mediating resistance to infection with ingested bacteria. Mice that were constitutively hypochlorhydric due to a mutation in a gastric H + /K + -ATPase (proton pump) gene were infected with Yersinia enterocolitica, Salmonella enterica serovar Typhimurium, Citrobacter rodentium , or Clostridium perfringens cells or spores. Significantly greater numbers of Yersinia, Salmonella , and Citrobacter cells ( P ≤ 0.006) and Clostridium spores ( P = 0.02) survived in hypochlorhydric mice, resulting in reduced median infectious doses. Experiments involving intraperitoneal infection or infection of mice treated with antacids indicated that the increased sensitivity of hypochlorhydric mice to infection was entirely due to the absence of stomach acid. Apart from establishing the role of gastric acid in nonspecific immunity to ingested bacterial pathogens, our model provides an excellent system with which to investigate the effects of hypochlorhydria on susceptibility to infection and to evaluate the in vivo susceptibility to gastric acid of orally administered therapies, such as vaccines and probiotics.

Genetic organization of the she pathogenicity island in Shigella flexneri 2a

Publisher: Elsevier BV

Date: 2001

DOI: 10.1006/MPAT.2000.0404

Dynamics of antimicrobial resistance in intestinal Escherichia coli from children in community settings in South Asia and sub-Saharan Africa

Publisher: Springer Science and Business Media LLC

Date: 20-08-2018

DOI: 10.1038/S41564-018-0217-4

Abstract: The dynamics of antimicrobial resistance (AMR) in developing countries are poorly understood, especially in community settings, due to a sparsity of data on AMR prevalence and genetics. We used a combination of phenotyping, genomics and antimicrobial usage data to investigate patterns of AMR amongst atypical enteropathogenic Escherichia coli (aEPEC) strains isolated from children younger than five years old in seven developing countries (four in sub-Saharan Africa and three in South Asia) over a three-year period. We detected high rates of AMR, with 65% of isolates displaying resistance to three or more drug classes. Whole-genome sequencing revealed a ersity of known genetic mechanisms for AMR that accounted for % of phenotypic resistance, with comparable rates amongst aEPEC strains associated with diarrhoea or asymptomatic carriage. Genetic determinants of AMR were associated with the geographic location of isolates, not E. coli lineage, and AMR genes were frequently co-located, potentially enabling the acquisition of multi-drug resistance in a single step. Comparison of AMR with antimicrobial usage data showed that the prevalence of resistance to fluoroquinolones and third-generation cephalosporins was correlated with usage, which was higher in South Asia than in Africa. This study provides much-needed insights into the frequency and mechanisms of AMR in intestinal E. coli in children living in community settings in developing countries.

Shiga Toxin–producing Escherichia coli Strains Negative for Locus of Enterocyte Effacement

Publisher: Centers for Disease Control and Prevention (CDC)

Date: 03-2017

DOI: 10.3201/EID1502.080631

Assembly of the type II secretion system such as found in Vibrio cholerae depends on the novel Pilotin AspS.

Publisher: Public Library of Science (PLoS)

Date: 10-01-2013

DOI: 10.1371/JOURNAL.PPAT.1003117