Program Schedule

Antiseptic tolerance and antimicrobial susceptibility of nosocomial Staphylococcus aureus at Texas Children’s Hospital:  2007-2013

Session: Poster Abstract Session: Pediatric Healthcare – associated Infection Epidemiology and Prevention
Friday, October 10, 2014
Room: The Pennsylvania Convention Center: IDExpo Hall BC
  • nosocomial qac poster.pdf (298.5 kB)
  • Background: Antiseptics such as chlorhexidine have been utilized to decrease the incidence of healthcare associated infections.  A number of genes in S. aureus, notably qacA/B and smr, have been associated with tolerance to antiseptics.  Work at our institution has revealed the emergence of S. aureus possessing these genes among pediatric cancer and cardiac surgery patients.  We examined the prevalence of antiseptic tolerant S. aureus among all nosocomial isolates at our institution as well as provided molecular and clinical characterization of these organisms.

    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.

    Jonathon Mcneil, MD1, Eric Kok2, Kristina Hulten, PhD3, Edward O. Mason Jr., PhD3 and Sheldon L. Kaplan, MD, FIDSA3, (1)Pediatrics, Baylor College of Medicine and Texas Children's Hospital, Houston, TX, Houston, TX, (2)Baylor College of Medicine and Texas Children's Hospital, Houston, TX, (3)Pediatrics, Baylor College of Medicine and Texas Children's Hospital, Houston, TX


    J. Mcneil, None

    E. Kok, None

    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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