ORCID Profile
0000-0001-9751-9877
Current Organisation
University of Melbourne
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Publisher: SAGE Publications
Date: 14-06-2022
DOI: 10.1177/17571774221107293
Abstract: Free online tools for bacterial genome analyses are available for local infection surveillance at hospitals. The tools do not require bioinformatic expertise and provide rapid actionable results. Within half a year carbapenemase producing Enterobacter cloacae was reported in clinical s les from three patients who had been hospitalized at the same ward. The aim of this outbreak investigation was to characterize and compare genomes of the isolated bacteria in order to determine molecular evidence of hospital transmission. The three isolates and two isolates reported as susceptible to carbapenems were locally analyzed by whole genome sequencing (WGS). Draft genome assembly, species identification, phylogenetic analyses, typing, resistance gene determination, and plasmid analyses were carried out using free online tools from the Center for Genomic Epidemiology (CGE). Genome analyses identified all three suspected outbreak isolates as E. hormaechei carrying bla OXA-436 gene. Two of the suspected outbreak isolates were closely related, while one was substantially different from them. Horizontal transfer of plasmid may have taken place in the ward. Detailed knowledge on the genomic composition of bacteria in suspected hospital outbreaks can be obtained by free online tools and may reveal transfer of resistance genes between different strains in addition to dissemination of specific clones.
Publisher: Springer Science and Business Media LLC
Date: 06-10-2020
DOI: 10.1038/S41467-020-18700-5
Abstract: The re-emergence of scarlet fever poses a new global public health threat. The capacity of North-East Asian serotype M12 ( emm 12) Streptococcus pyogenes (group A Streptococcus , GAS) to cause scarlet fever has been linked epidemiologically to the presence of novel prophages, including prophage ΦHKU.vir encoding the secreted superantigens SSA and SpeC and the DNase Spd1. Here, we report the molecular characterization of ΦHKU.vir-encoded exotoxins. We demonstrate that streptolysin O (SLO)-induced glutathione efflux from host cellular stores is a previously unappreciated GAS virulence mechanism that promotes SSA release and activity, representing the first description of a thiol-activated bacterial superantigen. Spd1 is required for resistance to neutrophil killing. Investigating single, double and triple isogenic knockout mutants of the ΦHKU.vir-encoded exotoxins, we find that SpeC and Spd1 act synergistically to facilitate nasopharyngeal colonization in a mouse model. These results offer insight into the pathogenesis of scarlet fever-causing GAS mediated by prophage ΦHKU.vir exotoxins.
Publisher: Cold Spring Harbor Laboratory
Date: 30-08-2023
DOI: 10.1101/2023.08.29.555273
Abstract: Populations of bacterial pathogens are made of strains that often have variable gene content, termed the pangenome. Variations in the genetic makeup of a single strain can alter bacterial physiology and fitness in response to different environmental stimuli. To define biologically relevant genes within a genome, genome-wide knockout transposon mutant libraries have been used to identify genes essential for survival or virulence in a particular strain. Such phenotypic studies have been applied in four different genotypes of the major human pathogen Streptococcus pyogenes, yet challenges exist in comparing results across studies conducted in different genetic backgrounds and conditions. To advance genotype-phenotype inferences within a population genomic framework of 250 S. pyogenes reference genomes, we systematically re-analysed publicly available transposon sequencing datasets from S. pyogenes using a transposon sequencing specific analysis pipeline, Transit. Across 4 genetic backgrounds and 9 phenotypic conditions, 311 genes were highly essential for survival, corresponding to ~22% of the core genome. Among the 311 genes, functions related to information storage, and processing were overrepresented. Genes associated with cellular processing and signalling were of significantly higher essentiality under in vivo conditions (animal models with differing disease manifestation and site of colonisation) compared to in vitro (varying types of culture media). Finally, essential operons across S. pyogenes genotypes were defined, with an increased number of essential operons detected under in vivo conditions. This study provides an extendible database to which new studies can be added, and a searchable html-based resource to direct future investigations into S. pyogenes population biology.
Publisher: Frontiers Media SA
Date: 03-05-2022
DOI: 10.3389/FMICB.2022.895942
Abstract: Free fatty acids (FFAs) are known to exhibit antimicrobial and anti-virulent properties against bacterial pathogens. Specific FFAs, such as lauric acid (LA C12:0), exert both effects against the foodborne pathogen Listeria monocytogenes : at low levels, LA acts to inhibit the activity of the virulence regulator PrfA, whereas at higher levels, LA inhibits bacterial growth. Deletion of prfA is known to promote tolerance toward antimicrobial FFAs, suggesting that the response of L. monocytogenes to anti-virulent and antimicrobial FFAs could be linked. In this study, we explored the response of L. monocytogenes toward antimicrobial FFAs holding an anti-virulence activity by isolating strains that can grow at high concentrations of LA. We found that LA-tolerant isolates carry mutations in the gene encoding the global regulator CcpA. Importantly, we discovered that mutation or deletion of ccpA protect L. monocytogenes against the antimicrobial activity of FFAs, whereas the ccpA mutants remain sensitive toward FFA’s PrfA inhibitory effect. A regulatory link involving CcpA, connecting the response toward the antimicrobial and anti-virulence activities of FFAs, is therefore unlikely. To further study how deletion of ccpA promotes FFA tolerance, we performed a transcriptomic analysis of the response to LA. Our data indicated that the FFA-tolerant phenotype of the ∆ ccpA strain is not induced upon LA exposure but appears to be an inherent phenotypic trait of the ccpA deletion mutation. Interestingly, we found that the bacterial surface of L. monocytogenes becomes more hydrophilic upon deletion of ccpA , and we demonstrate that CcpA plays a role in the response of L. monocytogenes to other stress conditions, including low pH and antibiotics. Altogether, our study revealed that regulatory activities of CcpA lead to an increased hydrophobicity of the bacterial surface, which may confer sensitivity of L. monocytogenes against the antimicrobial activity of FFAs. Notably, CcpA is not involved in responding to the PrfA inhibitory effect of FFAs, showing that FFA-tolerant strains can still be targeted by the anti-virulent activity of FFAs.
Publisher: Springer Science and Business Media LLC
Date: 24-02-2023
DOI: 10.1038/S41467-023-36717-4
Abstract: A new variant of Streptococcus pyogenes serotype M1 (designated ‘M1 UK ’) has been reported in the United Kingdom, linked with seasonal scarlet fever surges, marked increase in invasive infections, and exhibiting enhanced expression of the superantigen SpeA. The progenitor S. pyogenes ‘M1 global ’ and M1 UK clones can be differentiated by 27 SNPs and 4 indels, yet the mechanism for speA upregulation is unknown. Here we investigate the previously unappreciated expansion of M1 UK in Australia, now isolated from the majority of serious infections caused by serotype M1 S. pyogenes . M1 UK sub-lineages circulating in Australia also contain a novel toxin repertoire associated with epidemic scarlet fever causing S. pyogenes in Asia. A single SNP in the 5’ transcriptional leader sequence of the transfer-messenger RNA gene ssrA drives enhanced SpeA superantigen expression as a result of ssrA terminator read-through in the M1 UK lineage. This represents a previously unappreciated mechanism of toxin expression and urges enhanced international surveillance.
Publisher: Elsevier BV
Date: 12-2020
Publisher: Springer Science and Business Media LLC
Date: 09-03-2023
Publisher: The Open Journal
Date: 30-11-2022
DOI: 10.21105/JOSS.04910
Publisher: American Society for Microbiology
Date: 28-06-2022
Abstract: During infection, microbes must escape host immune responses and survive exposure to reactive oxygen species produced by immune cells. Here, we identify the ABC transporter substrate binding protein GshT as a key component of the glutathione salvage pathway in glutathione-auxotrophic GAS.
Publisher: The Open Journal
Date: 13-07-2022
DOI: 10.21105/JOSS.04369
No related grants have been discovered for Magnus Jespersen.