ORCID Profile
0000-0001-5751-8503
Current Organisation
University of Melbourne
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Publisher: Microbiology Society
Date: 20-09-2016
Publisher: American Society for Microbiology
Date: 11-2018
DOI: 10.1128/AAC.00898-18
Abstract: Coagulase-negative staphylococci (CoNS), such as Staphylococcus capitis , are major causes of bloodstream infections in neonatal intensive care units (NICUs). Recently, a distinct clone of S. capitis (designated S. capitis NRCS-A) has emerged as an important pathogen in NICUs internationally.
Publisher: American Chemical Society (ACS)
Date: 26-08-2021
Publisher: Cold Spring Harbor Laboratory
Date: 28-02-2023
DOI: 10.1101/2023.02.27.530350
Abstract: Among the 16 two-component systems (TCSs) in the opportunistic human pathogen Staphylococcus aureus , only WalKR is essential. Like orthologous systems in other Bacillota, S. aureus WalKR controls autolysins involved in peptidoglycan remodelling and is therefore intimately involved in cell ision. However, despite the importance of WalKR in S. aureus , the basis for its essentiality is not understood and the regulon poorly defined. Here, we defined a consensus WalR DNA-binding motif and the direct WalKR regulon by using functional genomics, including ChIP-seq, with a panel of isogenic walKR mutants that had a spectrum of altered activities. Consistent with prior findings, the direct regulon includes multiple autolysin genes. However, this work also revealed that WalR directly regulates at least five essential genes involved in lipoteichoic acid synthesis ( ltaS ) translation (rplK ) DNA compaction ( hup ) initiation of DNA replication ( dnaA, hup ) and purine nucleotide metabolism ( prs ). Thus, WalKR in S. aureus serves as a polyfunctional regulator that contributes to fundamental control over critical cell processes by co-ordinately linking cell wall homeostasis with purine biosynthesis, protein biosynthesis, and DNA replication. Collectively, our findings address the essentiality of this locus and highlight the importance of WalKR as a bona fide target for novel anti-staphylococcal therapeutics.
Publisher: Springer Science and Business Media LLC
Date: 14-10-2023
Publisher: Elsevier BV
Date: 05-2017
DOI: 10.1016/J.IJANTIMICAG.2017.12.019
Abstract: The molecular mechanisms and characteristics of rif icin (RIF) resistance in Staphylococcus epidermidis are poorly characterised, even though S. epidermidis is one of the most common nosocomial pathogens associated with indwelling medical device-related infections. The aim of this study was to investigate the evolution of RIF resistance and to characterise the associated molecular mechanisms in S. epidermidis. RIF-resistant mutants from two RIF-susceptible S. epidermidis strains (RP62A and IDRL-8883) were selected through in vitro and in vivo exposure to RIF. A total of 16 colonies with an RP62A background and 63 colonies with an IDRL-8883 background were analysed for rpoB mutations. The fitness of RIF-susceptible and isogenic RIF-resistant strains was assessed using a paired competition assay and by comparing generation times. All mutations detected were in cluster I of rpoB. The following five amino acid substitutions were selected in vitro: Asp471→Asn Asp471→Gly Asp471→Val Ser486→Tyr and His481→Tyr. The following three amino acid substitutions were selected in vivo: His481→Tyr Gln468→Lys and Ser486→Phe. Asp471→Asn and Asp471→Gly changes were associated with susceptible minimal inhibitory concentrations (MICs). In vitro competition assays revealed that all RIF-resistant mutants other than Ser486→Tyr and Ser486→Phe had a relative fitness of <1.0. His481→Tyr mutations had their own specific fitness costs and effects on growth rate, irrespective of strain background. In conclusion, the current study presents molecular characterisations and fitness costs of several rpoB mutations in S. epidermidis.
Publisher: Springer Science and Business Media LLC
Date: 03-09-2018
Publisher: Frontiers Media SA
Date: 16-03-2021
DOI: 10.3389/FMICB.2021.637656
Abstract: Multidrug-resistant Staphylococcus and vancomycin-resistant Enterococcus (VRE) are important human pathogens that are resistant to most clinical antibiotics. Treatment options are limited and often require the use of ‘last-line’ antimicrobials such as linezolid, daptomycin, and in the case of Staphylococcus , also vancomycin. The emergence of resistance to these last-line antimicrobial agents is therefore of considerable clinical concern. This mini-review provides an overview of resistance to last-line antimicrobial agents in Staphylococcus and VRE, with a particular focus on how genomics has provided critical insights into the emergence of resistant clones, the molecular mechanisms of resistance, and the importance of mobile genetic elements in the global spread of resistance to linezolid.
Publisher: Microbiology Society
Date: 09-2020
DOI: 10.1099/JMM.0.001238
Abstract: Introduction. The SARS-CoV-2 pandemic of 2020 has resulted in unparalleled requirements for RNA extraction kits and enzymes required for virus detection, leading to global shortages. This has necessitated the exploration of alternative diagnostic options to alleviate supply chain issues. Aim. To establish and validate a reverse transcription loop-mediated isothermal lification (RT- LAMP) assay for the detection of SARS-CoV-2 from nasopharyngeal swabs. Methodology. We used a commercial RT-LAMP mastermix from OptiGene in combination with a primer set designed to detect the CDC N1 region of the SARS-CoV-2 nucleocapsid (N) gene. A single-tube, single-step fluorescence assay was implemented whereby 1 µl of universal transport medium (UTM) directly from a nasopharyngeal swab could be used as template, bypassing the requirement for RNA purification. Amplification and detection could be conducted in any thermocycler capable of holding 65 °C for 30 min and measure fluorescence in the FAM channel at 1 min intervals. Results. Assay evaluation by assessment of 157 clinical specimens previously screened by E-gene RT-qPCR revealed assay sensitivity and specificity of 87 and 100%, respectively. Results were fast, with an average time-to-positive (Tp) for 93 clinical s les of 14 min ( sd ±7 min). Using dilutions of SARS-CoV-2 virus spiked into UTM, we also evaluated assay performance against FDA guidelines for implementation of emergency-use diagnostics and established a limit-of-detection of 54 Tissue Culture Infectious Dose 50 per ml (TCID 50 ml −1 ), with satisfactory assay sensitivity and specificity. A comparison of 20 clinical specimens between four laboratories showed excellent interlaboratory concordance performing equally well on three different, commonly used thermocyclers, pointing to the robustness of the assay. Conclusion. With a simplified workflow, The N1 gene Single Tube Optigene LAMP assay (N1-STOP-LAMP) is a powerful, scalable option for specific and rapid detection of SARS-CoV-2 and an additional resource in the diagnostic armamentarium against COVID-19.
Publisher: American Society for Microbiology
Date: 16-10-2023
Publisher: Springer Science and Business Media LLC
Date: 11-07-2019
DOI: 10.1038/S41467-019-10932-4
Abstract: WalKR (YycFG) is the only essential two-component regulator in the human pathogen Staphylococcus aureus . WalKR regulates peptidoglycan synthesis, but this function alone does not explain its essentiality. Here, to further understand WalKR function, we investigate a suppressor mutant that arose when WalKR activity was impaired a histidine to tyrosine substitution (H271Y) in the cytoplasmic Per-Arnt-Sim (PAS CYT ) domain of the histidine kinase WalK. Introducing the WalK H271Y mutation into wild-type S. aureus activates the WalKR regulon. Structural analyses of the WalK PAS CYT domain reveal a metal-binding site, in which a zinc ion (Zn 2+ ) is tetrahedrally-coordinated by four amino acids including H271. The WalK H271Y mutation abrogates metal binding, increasing WalK kinase activity and WalR phosphorylation. Thus, Zn 2+ -binding negatively regulates WalKR. Promoter-reporter experiments using S. aureus confirm Zn 2+ sensing by this system. Identification of a metal ligand recognized by the WalKR system broadens our understanding of this critical S. aureus regulon.
Publisher: Springer Science and Business Media LLC
Date: 17-09-2019
DOI: 10.1038/S41598-019-49981-6
Abstract: Staphylococcus aureus is a major cause of bovine mastitis, commonly leading to long-lasting, persistent and recurrent infections. Thereby, S . aureus constantly refines and permanently adapts to the bovine udder environment. In this work, we followed S . aureus within-host adaptation over the course of three months in a naturally infected dairy cattle with chronic, subclinical mastitis. Whole genome sequence analysis revealed a complete replacement of the initial predominant variant by another isogenic variant. We report for the first time within-host evolution towards a sigma factor SigB-deficient pathotype in S . aureus bovine mastitis, associated with a single nucleotide polymorphism in rsbU (G368A → G122D), a contributor to SigB-functionality. The emerged SigB-deficient pathotype exhibits a substantial shift to new phenotypic traits comprising strong proteolytic activity and poly- N -acetylglucosamine (PNAG)-based biofilm production. This possibly unlocks new nutritional resources and promotes immune evasion, presumably facilitating extracellular persistence within the host. Moreover, we observed an adaptation towards attenuated virulence using a mouse infection model. This study extends the role of sigma factor SigB in S . aureus pathogenesis, so far described to be required for intracellular persistence during chronic infections. Our findings suggest that S . aureus SigB-deficiency is an alternative mechanism for persistence and underpin the clinical relevance of staphylococcal SigB-deficient variants which are consistently isolated during human chronic infections.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 08-2018
DOI: 10.1126/SCITRANSLMED.AAR6115
Abstract: Alcohol-based disinfectants and particularly hand rubs are a key way to control hospital infections worldwide. Such disinfectants restrict transmission of pathogens, such as multidrug-resistant
Publisher: American Society for Microbiology
Date: 24-12-2019
Abstract: Staphylococcus epidermidis is a major cause of hospital-acquired infections, especially those related to implanted medical devices. Understanding how S. epidermidis causes disease and devising ways to combat these infections have been hindered by an inability to genetically manipulate clinically significant hospital-adapted strains. Here, we provide the first comprehensive analyses of the barriers to the uptake of foreign DNA in S. epidermidis and demonstrate that these are distinct from those described for S. aureus . Using these insights, we demonstrate an efficient approach for the genetic manipulation of S. epidermidis to enable the study of clinical isolates for the first time.
Publisher: Cambridge University Press (CUP)
Date: 19-03-2021
DOI: 10.1017/ICE.2021.120
Publisher: Cold Spring Harbor Laboratory
Date: 30-04-2020
DOI: 10.1101/2020.04.28.067363
Abstract: 2. The SARS-CoV-2 pandemic of 2020 has resulted in unparalleled requirements for RNA extraction kits and enzymes required for virus detection, leading to global shortages. This has necessitated the exploration of alternative diagnostic options to alleviate supply chain issues. To establish and validate a reverse transcription loop-mediated isothermal lification (RT-LAMP) assay for the detection of SARS-CoV-2 from nasopharyngeal swabs. We used a commercial RT-LAMP mastermix from OptiGene Ltd in combination with a primer set designed to detect the CDC N1 region of the SARS-CoV-2 nucleocapsid (N) gene. A single-tube, single-step fluorescence assay was implemented whereby as little as 1 μL of universal transport medium (UTM) directly from a nasopharyngeal swab could be used as template, bypassing the requirement for RNA purification. Amplification and detection could be conducted in any thermocycler capable of holding 65°C for 30 minutes and measure fluorescence in the FAM channel at one-minute intervals. Assay evaluation by assessment of 157 clinical specimens previously screened by E-gene RT-qPCR revealed assay sensitivity and specificity of 87% and 100%, respectively. Results were fast, with an average time-to-positive (Tp) for 93 clinical s les of 14 minutes (SD ±7 minutes). Using dilutions of SARS-CoV-2 virus spiked into UTM, we also evaluated assay performance against FDA guidelines for implementation of emergency-use diagnostics and established a limit-of-detection of 54 Tissue Culture Infectious Dose 50 per ml (TCID 50 mL −1 ), with satisfactory assay sensitivity and specificity. A comparison of 20 clinical specimens between four laboratories showed excellent interlaboratory concordance performing equally well on three different, commonly used thermocyclers, pointing to the robustness of the assay. With a simplified workflow, N1-STOP-LAMP is a powerful, scalable option for specific and rapid detection of SARS-CoV-2 and an additional resource in the diagnostic armamentarium against COVID-19. 3. The authors confirm all supporting data, code and protocols have been provided within the article or through supplementary data files.
Publisher: Cold Spring Harbor Laboratory
Date: 05-03-2023
DOI: 10.1101/2023.03.01.23286614
Abstract: Bacterial pathogens such as vancomycin-resistant Enterococcus faecium (VREfm) that are resistant to almost all antibiotics are among the top global threats to human health. Daptomycin is a new last-resort antibiotic for VREfm infections with a novel mode-of-action, but for which resistance has surprisingly and alarmingly been widely reported. The causes of such a rapid emergence of resistance to this novel antibiotic have been unclear. Here we show that the use of rifaximin, an unrelated antibiotic used prophylactically to prevent hepatic encephalopathy in liver disease patients, is causing resistance to this last-resort antibiotic in VREfm. We show that mutations within the bacterial RNA polymerase complex confer cross- resistance to both rifaximin and daptomycin. Furthermore, VREfm with these mutations are spread globally across at least 5 continents and 20 countries, making this a major yet previously unrecognised mechanism of resistance. Until now, rifaximin has been considered ‘low-risk’ for development of antibiotic resistance. Our study shows this is not the case and that widespread rifaximin use may be compromising the clinical efficacy of daptomycin, one of the major last-resort interventions for multidrug resistant pathogens. These findings demonstrate that unanticipated antibiotic cross-resistance may potentially undermine global strategies designed to preserve the clinical use of last-resort antibiotics.
Publisher: Springer Science and Business Media LLC
Date: 27-01-2023
Publisher: AMPCo
Date: 02-2014
DOI: 10.5694/MJA13.10592
Publisher: Wiley
Date: 05-2014
DOI: 10.1111/IMJ.12409
Abstract: This retrospective case series identifies the largest cohort of non-O1, non-O139 Vibrio cholerae bacteraemia in an Australian population from 2000 to 2013. We examine the risk factors, epidemiology, clinical presentations and mortality of non-O1, non-O139 V. cholerae bacteraemia in Victoria and compare them with published cases in the literature. This case series highlights the pathogenic potential of non-O1, non-O139 V. cholerae and identifies possible associations with host (underlying chronic liver disease and malignancy) and environmental factors (contaminated water supply and raw seafood). Clinicians should be aware of the morbidity and mortality associated with invasive non-O1, non-O139 V. cholerae infections, particularly in immunocompromised patients.
Publisher: Informa UK Limited
Date: 06-05-2015
DOI: 10.1586/14787210.2015.1041924
Abstract: Clinicians treating an infection assess a patient in terms of disease manifestation, causative organism and available antibiotic options with the aim of devising a therapeutic strategy under the creed of 'first, do no harm'. It is often only when treatment is failing or options are limited, as in the scenario of multidrug-resistant organisms, that consideration is given to the interplay that occurs between the microbe and the host. The emergence of Staphylococcus aureus with reduced susceptibility to vancomycin provides a prime ex le of these dynamic interactions. This review shall explore these concepts in relation to vancomycin for the treatment of methicillin-resistant S. aureus, with the aim of providing an informed approach to the utilization of this drug.
No related grants have been discovered for Jean Lee.