Clinical and Microbiological Characteristics of Heteroresistant and Vancomycin-Intermediate Staphylococcus aureus from Bloodstream Infections in a Brazilian Teaching Hospital

PLoS One. 2016 Aug 30;11(8):e0160506. doi: 10.1371/journal.pone.0160506. eCollection 2016.

Abstract

This study analyzed clinical and microbiological characteristics of heteroresistant (hVISA) and vancomycin-intermediate Staphylococcus aureus (VISA) from bloodstream infections (BSI) in a Brazilian teaching hospital, between 2011 and 2013. Minimum inhibitory concentrations (MIC) of antimicrobials were determined by broth microdilution method and SCCmec was detected by PCR. Isolates with a vancomycin MIC ≥ 2mg/L were cultured on BHI agar with 3, 4 or 6 mg/L (BHIa3, BHIa4 or BHIa6) of vancomycin and BHIa4 with casein (BHIa4ca). Macromethod Etest® and Etest® Glicopeptides Resistance Detection were also used. VISA and hVISA isolates were confirmed by the population analysis profile then typed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing. Medical data from the patients were obtained from their medical records. Among 110 consecutive isolates, 31 (28%) were MRSA and carried the SCCmec type II (15 isolates) or IV (16 isolates). Vancomycin MIC50 and MIC90 were 1 and 2 mg/L, respectively. MRSA isolates had increased non-susceptibility to daptomycin (p = 0.0003). Six (5%) isolates were VISA, four of which were MRSA, three SCCmec type II/USA100/ST5 and one type IV/USA800/ST3192. One MRSA SCCmec II isolate grew on agar BHIa3, BHIa4 and BHIa4ca, and it was confirmed as hVISA. Among the six VISA isolates, five (83%) grew on BHIa3 and three (50%) on BHI4ca. Four of the six VISA isolates and the one hVISA isolate were from patients who had undergone dialysis. Thus, a possible dissemination of the SCCmec II/USA100/ST5 lineage may have occurred in the hospital comprising the VISA, hVISA and daptomycin non-susceptible S. aureus Brazilian isolates from health care associated bloodstream infections.

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Bacteremia / microbiology*
  • Cross Infection / microbiology
  • Female
  • Hospitals, Teaching
  • Humans
  • Male
  • Methicillin-Resistant Staphylococcus aureus / drug effects
  • Methicillin-Resistant Staphylococcus aureus / genetics
  • Methicillin-Resistant Staphylococcus aureus / isolation & purification
  • Microbial Sensitivity Tests
  • Multilocus Sequence Typing
  • Renal Dialysis / adverse effects
  • Staphylococcal Infections / microbiology*
  • Staphylococcus aureus / classification
  • Staphylococcus aureus / drug effects
  • Staphylococcus aureus / genetics
  • Staphylococcus aureus / isolation & purification*
  • Vancomycin Resistance*

Substances

  • Anti-Bacterial Agents

Grants and funding

This work was supported by grants of Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro to KRNS and SAN; Conselho Nacional de Desenvolvimento Científico e Tecnológico to KRNS, TMC, PGMM and FSC. APD is sponsored by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.