title: Prevalence of vancomycin-intermediate Staphylococcus aureus (VISA) and heterogeneous VISA among methicillin-resistant S. aureus with high vancomycin minimal inhibitory concentrations in Taiwan: A multicenter surveillance study, 2012-2013.
abstract: OBJECTIVE
  Intermediate-resistance and heteroresistance to vancomycin in methicillin-resistant Staphylococcus aureus (MRSA) is reported worldwide. A surveillance study in 2003 showed that the prevalence rates of vancomycin-intermediate S. aureus (VISA) and heterogeneous VISA (hVISA) in Taiwan were 0.2% and 0.7%, respectively. This study aimed to investigate the updated prevalence of VISA and hVISA in Taiwan.
  
  
  METHODS
  MRSA isolates from sterile sites with minimal inhibitory concentrations (MICs) of 1 μg/mL or more to vancomycin were collected from 15 participating hospitals in Taiwan. Enrolled MRSA isolates were submitted to antimicrobial susceptibility testing, staphylococcal cassette chromosome mec (SCCmec) element typing, and multilocus sequence typing. Isolates with vancomycin MIC of 1 μg/mL or 2 μg/mL were screened for vancomycin heterogeneous resistance by Etest glycopeptide-resistance detection (GRD). Those with positive GRD screening results were then analyzed by modified population analysis profiling-area under the curve method for confirmation of vancomycin heteroresistance.
  
  
  RESULTS
  Between 2012 and 2013, a total of 622 MRSA isolates from sterile sites with vancomycin MIC of 1 μg/mL or more were studied. The prevalence rates of hVISA and VISA among these isolates were 10.0% and 2.7%, respectively. The hVISA prevalence increased significantly compared to that in 2003. Compared with vancomycin-susceptible S. aureus, hVISA and VISA isolates were less susceptible to ciprofloxacin, clindamycin, daptomycin, gentamicin, rifampin, and trimethoprim/sulfamethoxazole, and are thus, more likely to have SCCmec II or III element. A twofold increase in either vancomycin or teicoplanin MIC doubled the probability of being hVISA.
  
  
  CONCLUSIONS
  Growing hVISA prevalence was highly suspected. Longitudinal surveillance of this phenomenon and monitoring of its clinical impact are necessary.
authors: Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
authors: Sung-Hsi
authors: SH
authors: Huang
authors: Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
authors: Yee-Chun
authors: YC
authors: Chen
authors: Department of Medical Research, Chi Mei Medical Center, Tainan County, Taiwan.
authors: Yin-Ching
authors: YC
authors: Chuang
authors: Division of Infectious Diseases and Tropical Medicine, Department of Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.
authors: Sheng-Kang
authors: SK
authors: Chiu
authors: Section of Infectious Diseases, Department of Medicine, Taipei Veterans General Hospital, National Yan-Ming University, Taipei, Taiwan.
authors: Chang-Phone
authors: CP
authors: Fung
authors: Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors: Po-Liang
authors: PL
authors: Lu
authors: Department of Infectious Diseases, Buddhist Tzu Chi General Hospital, Hualien, Taiwan.
authors: Lih-Shinn
authors: LS
authors: Wang
authors: Department of Laboratory Medicine, Chang Gung Memorial Hospital, Kweishan, Taoyuan, Taiwan.
authors: Tsu-Lan
authors: TL
authors: Wu
authors: Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan. Electronic address: wang.jt1968@gmail.com.
authors: Jann-Tay
authors: JT
authors: Wang
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015373:Bacterial Typing Techniques; D024901:Drug Resistance, Multiple, Bacterial; D006801:Humans; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D058885:Multilocus Sequence Typing; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000453:epidemiology*; D013624:Taiwan / Q000453:epidemiology; D014640:Vancomycin / Q000494:pharmacology*; D020713:Vancomycin Resistance
chemical_list: D000900:Anti-Bacterial Agents; D014640:Vancomycin
keywords: Taiwan; epidemiology; heterogeneous vancomycin-intermediate Staphylococcus aureus