Antiseptic tolerance and antimicrobial susceptibility of nosocomial Staphylococcus aureus at Texas Children’s Hospital: 2007-2013
Methods: Isolates were obtained from an ongoing prospective S. aureus surveillance study; isolates obtained after more than 72 hours of hospitalization during the years 2007-2013 were identified. Antimicrobial susceptibility was determined by the clinical microbiology lab in the routine course of clinical care. All isolates underwent PCR for the antiseptic tolerance genes qacA/B and smr; isolates positive by PCR were further characterized by PFGE.
Results: 280 isolates were included in the study of which 114 (40.7%) were methicillin-resistant (MRSA). The median age of patients was 3.3 months (IQR: 0.9-73.2). Ninety isolates (32.1%) were positive for smr while 61 (21.4%) were positive for qacA/B; 28 isolates (10%) carried both genes. The proportion of isolates positive for these genes varied from year-to-year but was lowest in 2007 (<5%) and was highest for smr in 2009 (92%) and for qacA/B (87.2%) in 2013. smr positive isolates were more often MRSA (53.3% vs 34.7%, p 0.004), clindamycin resistant (33.3% vs 24.7%, p 0.08) and associated with invasive infections (78.9% vs 64.7%, p 0.01). qacA/B positive isolates were more often associated with the diagnosis of bacteremia specifically (50.8% vs 35.6% p 0.03). The most common PFGE type among antiseptic tolerant isolates was USA300 (20%); numerous other pulsotypes accounted for the remainder of isolates.
Conclusion: S. aureus possessing antiseptic tolerant genes are common among nosocomial isolates at our institution. These isolates are more often associated with a multidrug resistant phenotype and more severe infections. These trends should be monitored in light of the continued use of antiseptics both in the hospital and community settings.
K. Hulten, None
E. O. Mason Jr., None
S. L. Kaplan, Pfizer: Grant Investigator, Research grant
Cerexa: Grant Investigator, Research grant
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