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Henry Chow

Bio: Henry Chow is an academic researcher from The Chinese University of Hong Kong. The author has contributed to research in topics: SCCmec & Methicillin-resistant Staphylococcus aureus. The author has an hindex of 1, co-authored 1 publications receiving 756 citations.

Papers
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Journal ArticleDOI
06 Apr 2011-PLOS ONE
TL;DR: A high level of biodiversity among MRSA, especially among strains harbouring SCCmec IV and V elements is shown, and the data indicate a high rate of genetic recombination in MRSA involving SCC elements, bacteriophages or other mobile genetic elements and large-scale chromosomal replacements.
Abstract: In recent years, methicillin-resistant Staphylococcus aureus (MRSA) have become a truly global challenge. In addition to the long-known healthcare-associated clones, novel strains have also emerged outside of the hospital settings, in the community as well as in livestock. The emergence and spread of virulent clones expressing Panton-Valentine leukocidin (PVL) is an additional cause for concern. In order to provide an overview of pandemic, epidemic and sporadic strains, more than 3,000 clinical and veterinary isolates of MRSA mainly from Germany, the United Kingdom, Ireland, France, Malta, Abu Dhabi, Hong Kong, Australia, Trinidad & Tobago as well as some reference strains from the United States have been genotyped by DNA microarray analysis. This technique allowed the assignment of the MRSA isolates to 34 distinct lineages which can be clearly defined based on non-mobile genes. The results were in accordance with data from multilocus sequence typing. More than 100 different strains were distinguished based on affiliation to these lineages, SCCmec type and the presence or absence of PVL. These strains are described here mainly with regard to clinically relevant antimicrobial resistance- and virulence-associated markers, but also in relation to epidemiology and geographic distribution. The findings of the study show a high level of biodiversity among MRSA, especially among strains harbouring SCCmec IV and V elements. The data also indicate a high rate of genetic recombination in MRSA involving SCC elements, bacteriophages or other mobile genetic elements and large-scale chromosomal replacements.

834 citations


Cited by
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Journal ArticleDOI
TL;DR: The origin of MRSA is described, with emphasis on the diverse nature of staphylococcal cassette chromosome mec (SCCmec).
Abstract: SUMMARY Staphylococcus aureus, a major human pathogen, has a collection of virulence factors and the ability to acquire resistance to most antibiotics. This ability is further augmented by constant emergence of new clones, making S. aureus a “superbug.” Clinical use of methicillin has led to the appearance of methicillin-resistant S. aureus (MRSA). The past few decades have witnessed the existence of new MRSA clones. Unlike traditional MRSA residing in hospitals, the new clones can invade community settings and infect people without predisposing risk factors. This evolution continues with the buildup of the MRSA reservoir in companion and food animals. This review focuses on imparting a better understanding of MRSA evolution and its molecular characterization and epidemiology. We first describe the origin of MRSA, with emphasis on the diverse nature of staphylococcal cassette chromosome mec (SCCmec). mecA and its new homologues (mecB, mecC, and mecD), SCCmec types (13 SCCmec types have been discovered to date), and their classification criteria are discussed. The review then describes various typing methods applied to study the molecular epidemiology and evolutionary nature of MRSA. Starting with the historical methods and continuing to the advanced whole-genome approaches, typing of collections of MRSA has shed light on the origin, spread, and evolutionary pathways of MRSA clones.

776 citations

Journal ArticleDOI
31 May 2018
TL;DR: The success of MRSA is a consequence of the extensive arsenal of virulence factors produced by S. aureus combined with β-lactam resistance and, for most clones, resistance to other antibiotic classes as discussed by the authors.
Abstract: Since the 1960s, methicillin-resistant Staphylococcus aureus (MRSA) has emerged, disseminated globally and become a leading cause of bacterial infections in both health-care and community settings. However, there is marked geographical variation in MRSA burden owing to several factors, including differences in local infection control practices and pathogen-specific characteristics of the circulating clones. Different MRSA clones have resulted from the independent acquisition of staphylococcal cassette chromosome mec (SCCmec), which contains genes encoding proteins that render the bacterium resistant to most β-lactam antibiotics (such as methicillin), by several S. aureus clones. The success of MRSA is a consequence of the extensive arsenal of virulence factors produced by S. aureus combined with β-lactam resistance and, for most clones, resistance to other antibiotic classes. Clinical manifestations of MRSA range from asymptomatic colonization of the nasal mucosa to mild skin and soft tissue infections to fulminant invasive disease with high mortality. Although treatment options for MRSA are limited, several new antimicrobials are under development. An understanding of colonization dynamics, routes of transmission, risk factors for progression to infection and conditions that promote the emergence of resistance will enable optimization of strategies to effectively control MRSA. Vaccine candidates are also under development and could become an effective prevention measure.

650 citations

Journal ArticleDOI
TL;DR: The group consensus was to recommend spa and staphylococcal cassette chromosome mec (SCCmec) typing as the preferred methods for MRSA, which are informative in defining particular strain characteristics and utilise standardised nomenclatures, making them applicable globally.

539 citations

Journal ArticleDOI
TL;DR: Current and new molecular typing methods for outbreak detection and epidemiological surveillance of bacterial pathogens in clinical practice are reviewed to give an overview of their specific advantages and disadvantages.
Abstract: Typing methods for discriminating different bacterial isolates of the same species are essential epidemiological tools in infection prevention and control. Traditional typing systems based on phenotypes, such as serotype, biotype, phage-type, or antibiogram, have been used for many years. However, more recent methods that examine the relatedness of isolates at a molecular level have revolutionised our ability to differentiate among bacterial types and subtypes. Importantly, the development of molecular methods has provided new tools for enhanced surveillance and outbreak detection. This has resulted in better implementation of rational infection control programmes and efficient allocation of resources across Europe. The emergence of benchtop sequencers using next generation sequencing technology makes bacterial whole genome sequencing (WGS) feasible even in small research and clinical laboratories. WGS has already been used for the characterisation of bacterial isolates in several large outbreaks in Europe and, in the near future, is likely to replace currently used typing methodologies due to its ultimate resolution. However, WGS is still too laborious and time-consuming to obtain useful data in routine surveillance. Also, a largely unresolved question is how genome sequences must be examined for epidemiological characterisation. In the coming years, the lessons learnt from currently used molecular methods will allow us to condense the WGS data into epidemiologically useful information. On this basis, we have reviewed current and new molecular typing methods for outbreak detection and epidemiological surveillance of bacterial pathogens in clinical practice, aiming to give an overview of their specific advantages and disadvantages.

490 citations

Journal ArticleDOI
TL;DR: There is a detectable bacterial community within human lung tissue that changes in patients with very severe COPD.
Abstract: Rationale: Based on surface brushings and bronchoalveolar lavage fluid, Hilty and coworkers demonstrated microbiomes in the human lung characteristic of asthma and chronic obstructive pulmonary disease (COPD), which have now been confirmed by others. Objectives: To extend these findings to human lung tissue samples. Methods: DNA from lung tissue samples was obtained from nonsmokers (n ¼ 8); smokers without COPD (n ¼ 8); patients with very severe COPD (Global Initiative for COPD [GOLD] 4) (n ¼ 8); and patientswithcysticfibrosis(CF)(n¼8).Thelatterservedasapositive control, with sterile water as a negative control. All bacterial community analyses were based on polymerase chain reaction amplifying16SrRNAgenefragments.Totalbacterialpopulationsweremeasured by quantitative polymerase chain reaction and bacterial community composition was assessed by terminal restriction fragment length polymorphism analysis and pyrotag sequencing. MeasurementandMainResults:Totalbacterialpopulationswithinlung tissue were small (20‐1,252 bacterial cells per 1,000 human cells) but greater in all four sample groups versus the negative control group (P,0.001).Terminalrestrictionfragmentlengthpolymorphismanalysis and sequencing distinguished three distinct bacterial community compositions: one common to the nonsmoker and smoker groups, asecondtotheGOLD4group,andthethirdtotheCF-positivecontrol group. Pyrotag sequencing identified greater than 1,400 unique bacterial sequences and showed an increase in the Firmicutes phylum in GOLD4patientsversusall othergroups (P,0.003) attributable to an increase in the Lactobacillus genus (P , 0.0007).

465 citations