Clinical and Molecular Features of Decreased Chlorhexidine Susceptibility among Nosocomial Staphylococcus aureus Isolates at Texas Children's Hospital
ABSTRACTOne of the strategies utilized to decrease infections in the hospital setting relies on topical antimicrobials and antiseptics. While their use is beneficial, concerns arise over the potential to develop resistance or tolerance to these agents. We examined nosocomialStaphylococcus aureusisolates from 2007 to 2013 for the presence of genes associated with tolerance to chlorhexidine. Isolates and patients were identified from anS. aureussurveillance study at Texas Children's Hospital. NosocomialS. aureusisolates (those causing infection at ≥72 h of hospitalization) were identified and underwent PCR for theqacAorqacB(qacA/B) andsmrgenes associated with elevated minimum bactericidal concentrations of chlorhexidine. Molecular typing with pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), andagrtyping and a review of the medical record were performed. Two hundred forty-seven nosocomialS. aureusinfections were identified. Overall, 111 isolates carried one or both genes (44.9%); 33.1% were positive forsmr, 22.7% were positive forqacA/B, and 10.9% of the isolates possessed both genes. Thesmr-positive isolates were more often resistant to methicillin, ciprofloxacin, and/or clindamycin. The isolates positive forqacA/Bwere more often associated with indwelling central venous catheters and a vancomycin MIC of ≥2 μg/ml. Isolates carrying eithersmrorqacA/Bwere associated with a diagnosis of bacteremia. Thesmr-positive isolates more often belonged to sequence type 8 (ST8) than the isolates that were positive forqacA/B. Mupirocin resistance was detected in 2.8% of the isolates. Antiseptic-tolerantS. aureusstrains are common in our children's hospital and are associated with decreased susceptibility to other systemic antimicrobials and with bloodstream infections. Further work is needed to understand the implications that these organisms have on the hospital environment and antiseptic use in the future.