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Emergence of methicillin-resistant Staphylococcus aureus carrying Panton–Valentine leukocidin gene in Shanghai, China

2006; Elsevier BV; Volume: 10; Issue: 6 Linguagem: Inglês

10.1016/j.ijid.2006.06.002

1878-3511

Guanghui Li, Yingyuan Zhang, Fu Wang, Yijian Chen, Carl Erik Nord, Hong Fang,

Streptococcal Infections and Treatments

Staphylococcus aureus is a major nosocomial pathogen that causes a range of infections. Methicillin-resistant S. aureus (MRSA) was first detected in the early 1960s, shortly after the introduction of methicillin, and it has become associated with hospital outbreaks globally. In recent years, infection caused by community-acquired MRSA (CA-MRSA) as an emerging infectious disease has been reported with increasing frequency around the world.1Vandenesch F. Naimi T. Enright M.C. Lina G. Nimmo G.R. Heffernan H. et al.Community-acquired methicillin-resistant Staphylococcus aureus carrying Panton–Valentine leukocidin genes: worldwide emergence.Emerg Infect Dis. 2003; 9: 978-984Crossref PubMed Scopus (1520) Google Scholar In Shanghai, China, the incidence of MRSA among S. aureus strains increased from 24% to 64% during a 20-year period from 1985 to 2004.2Zhu D.M. Wang F. Zhang Y.Y. Surveillance of bacterial resistance from hospitals in Shanghai in 2004.Chin J Infect Chemother. 2005; 5: 195-200Google Scholar In Asia, CA-MRSA strains have been identified in Japan, Singapore, Hong Kong, and Taiwan, however no report is available from mainland China, where the incidence of MRSA is high. Panton–Valentine leukocidin (PVL) is a cytotoxin of S. aureus that has been supposed to be associated with primary skin infections and community-acquired severe necrotic pneumonia.3Zetola N. Francis J.S. Nuermberger E.L. Bishai W.R. Community-acquired methicillin-resistant Staphylococcus aureus: an emerging threat.Lancet Infect Dis. 2005; 5: 275-286Abstract Full Text Full Text PDF PubMed Scopus (679) Google Scholar The aim of the present study was to screen for MRSA strains harboring the pvl gene isolated in Shanghai. A total of 114 MRSA isolates from Huashan Hospital, Shanghai, China during 1999 and 2005 were investigated in the study. Strains were collected from nine outpatients and from 105 inpatients. The isolates were recovered from wounds (79.8%), pus (10.5%), pleural liquid (5.3%), and blood (4.4%). The identities of the S. aureus isolates were confirmed by colony morphology, Gram-staining, and the coagulase test. Methicillin resistance was screened by oxacillin disk (1 μg).4National Committee for Clinical Laboratory Standards. Performance standards for antimicrobial disk susceptibility test; approved standards—8th edition. M2-A8/M7-A6 and supplemental tables M100-S14. Wayne, PA: National Committee for Clinical Laboratory Standards; 2003.Google Scholar The presence of mecA and nuc genes was verified by a duplex PCR. The minimum inhibitory concentrations (MICs) of the following eight antimicrobial agents were determined by broth microdilution method (dry-form commercial MIC panels, Sensititre, TREK Diagnostics, UK): dalbavancin, vancomycin, teicoplanin, linezolid, quinupristin–dalfopristin, oxacillin, ampicillin, and clindamycin. The results were interpreted according to Clinical and Laboratory Standards Institute (CLSI) criteria, except for dalbavancin, for which the susceptibility and resistance breakpoints have not yet been established.5Clinical and Laboratory Standards Institute. Performance standards for antimicrobial susceptibility testing M100-S15. Wayne, PA: Clinical and Laboratory Standards Institute; 2005.Google Scholar The detection of the pvl gene was carried out by a PCR assay as previously described.6Lina G. Piemont Y. Godail-Gamont F. Bes M. Peter M.-O. Gauduchon V. et al.Involvement of Panton–Valentine leukocidin-producing Staphylococcus aureus in primary skin infections and pneumonia.Clin Infect Dis. 1999; 29: 1128-1132Crossref PubMed Scopus (2087) Google Scholar pvl gene-positive strains were further investigated by molecular typing. The SCCmec typing was carried out by a PCR SCCmec typing scheme, i.e., mec complex and ccr complex typing according to Zhang et al.7Zhang K. McClure J.A. Elsayed S. Louie T. Conly J.M. Novel multiplex PCR assay for characterization and concomitant subtyping of staphylococcal cassette chromosome mec types I to V in methicillin-resistant Staphylococcus aureus.J Clin Microbiol. 2005; 43: 5026-5033Crossref PubMed Scopus (873) Google Scholar and PCR-restriction fragment length polymorphism (RFLP) method by Yang et al.8Yang J.A. Park D.W. Sohn J.W. Kim M.J. Novel PCR-restriction fragment length polymorphism analysis for rapid typing of staphylococcal cassette chromosome mec elements.J Clin Microbiol. 2006; 44: 236-238Crossref PubMed Scopus (14) Google Scholar The spa (staphylococcal protein A gene) typing was performed as previously described.9Harmsen D. Claus H. Witte W. Rothganger J. Claus H. Turnwald D. et al.Typing of methicillin-resistant Staphylococcus aureus in a university hospital setting by using novel software for spa repeat determination and database management.J Clin Microbiol. 2003; 41: 5442-5448Crossref PubMed Scopus (1357) Google Scholar DNA sequencing was conducted on a 310 Genetic Analyzer (Applied Biosystems). spa Types were analyzed with the Ridom StaphType software (Ridom GmbH, Würzburg, Germany). The susceptibilities of the 114 MRSA isolates to the eight antimicrobial agents are listed in Table 1. All the strains were susceptible to vancomycin, linezolid, quinupristin–dalfopristin, and dalbavancin, while five of them were intermediately susceptible to teicoplanin with MICs at 8 mg/L. The strains were resistant to oxacillin, ampicillin, and clindamycin.Table 1Susceptibilities of 114 MRSA strains to eight antimicrobial agents from Shanghai, ChinaAntibioticsMIC (mg/L)Percentage by categoryMIC rangeMIC50MIC90Susceptible %Intermediate %Resistant %Dalbavancin0.06–0.250.1250.125–––Vancomycin1–2221000.00.0Teicoplanin0.5–81295.64.40.0Linezolid1–2221000.00.0Quinupristin–dalfopristin0.25–20.511000.00.0Oxacillin>16>16>160.00.0100Ampicillin16–>16>16>160.00.0100Clindamycin>16>16>160.00.0100 Open table in a new tab Among the 114 MRSA strains, one was identified to be pvl gene positive, while all the others were negative. The pvl-positive strain was confirmed to carry SCCmec IV by both methods employed, and belonged to t318 in spa typing with a repeat succession 15-12-16-16-02-16-02-25-17-24. S. aureus with spa type t318 has been found in Cape Verde, the UK, Denmark, Norway, Belgium, Germany, and France (http://spa.ridom.de/frequencies.shtml). Further investigation is necessary for the clarification of the dissemination and frequency of this clone both locally and nationally. In the present study, the pvl-positive MRSA isolate was detected from a patient with a breast abscess. The case was a typical soft tissue infection that occurred in a previously healthy, young woman with no known risk factors for MRSA acquisition. According to the available case history, the infection was acquired outside the hospital setting, which was also supported by the genotypic findings for this strain. To our knowledge, this is the first report from mainland China of an infection caused by pvl-positive MRSA. Clinically, pvl-positive S. aureus shows a predilection for causing necrotic lesions of the skin and respiratory mucosa. In addition, the mortality associated with pvl-positive S. aureus has been shown to be significantly higher than that caused by pvl-negative S. aureus (37% vs. 6% at 48 hours).10Gillet Y. Issartel B. Vanhems P. Fournet J.C. Lina G. Bes M. et al.Association between Staphylococcus aureus strains carrying gene for Panton–Valentine leukocidin and highly lethal necrotising pneumonia in young immunocompetent patients.Lancet. 2002; 359: 753-759Abstract Full Text Full Text PDF PubMed Scopus (1271) Google Scholar MRSA isolates with reduced susceptibility to teicoplanin were also observed in the study, which has not yet been reported in Shanghai. Although the five isolates were intermediately susceptible to teicoplanin, this is a warning that S. aureus strains with full resistance might emerge in the future if this kind of antibiotic is widely used without control. Strict infection control practices, routine screening for resistance, and controlled use of antibacterial agents, especially glycopeptides, are critical steps in preventing the further development of resistance among staphylococci. In conclusion, this is the first reported case of an infection caused by MRSA carrying the Panton–Valentine leukocidin (PVL) gene in Shanghai, China. The emergence of such strains in Shanghai, a densely populated city with a high incidence of MRSA, indicates the necessity of epidemiological surveillance of these clinically important strains. Conflict of interest: No conflict of interest to declare.