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Volume 45, Number 6, December 2012

Molecular epidemiology and clinical characteristics of hetero-resistant vancomycin intermediate Staphylococcus aureus bacteremia in a Taiwan Medical Center


Shang-Yi Lin, Tun-Chieh Chen, Feng-Jui Chen, Yen-Hsu Chen, Yee-In Lin, L. Kristopher Siu, Po-Liang Lu


Received: April 1, 2011    Revised: July 14, 2011    Accepted: July 3, 2011   

 

Corresponding author:
  • Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan
  • Laboratory Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan
  • School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
  • Corresponding Author InformationCorresponding author. Department of Internal Medicine, Kaohsiung Medical University Hospital, 100 Tzyou 1st Road, Kaohsiung City, Taiwan.


 

Background and purpose: 

Hetero-resistant vancomycin intermediate Staphylococcus aureus (hVISA) emerges worldwide in recent decade. The purpose of this study was to investigate the glycopeptide usage trend, the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) with reduced vancomycin susceptibility, the susceptible rates to newer antimicrobials, molecular epidemiology, clinical characteristics, as well as patient outcome among S. aureus bacteremia cases in a Taiwanese medical center.



 

Methods:

From March to December 2009, among 118 S. aureus blood isolates in a Taiwanese medical center, 62 MRSA isolates were screened for hVISA by Etest macromethod and further confirmed with modified population analysis profiling method. Molecular typing of hVISA isolates was performed.



 

Results:

Five (4.2%) isolates were hVISA. Compared with non-hVISA MRSA, hVISA isolates had higher resistant rates to ciprofloxacin, gentamicin, trimethoprim/sulfamethoxazole, and tetracycline. Among the MRSA infected, patients infected with hVISA had a higher in-hospital mortality rate than non-hVISA group (60% vs. 17.5%, p = 0.025). All hVISA isolates were nosocomial and had different pulsed field gel electrophoresis pulsotype. Four hVISA isolates carried type III staphylococcal cassette chromosome mec (SCCmec) and the remaining isolate carried SCCmec type II. Three of the 5 hVISA isolates belonged to sequence type 239, which is the most common type in Taiwan. Glycopeptide usage increased in the study hospital; however, these hVISA-infected patients did not receive glycopeptide treatment in the recent 6 months.



 

Conclusion:

Our results suggested hVISA might have disseminated in the hospital before we observed this highest hVISA rate in Taiwan and increasing glycopeptide usage might serve as selection pressure. Measures to prevent the transmission of MRSA with reduced vancomycin susceptibility and to treat such infection were urgently needed.



 

Key words:

GlycopeptideHetero-resistant vancomycin intermediate Staphylococcus aureusStaphylococcal cassette chromosomes