130. Decreased susceptibility to retapamulin, mupirocin and chlorhexidine among Staphylococcus aureus isolates causing skin-and-soft-tissue infection in otherwise healthy children
Session: Oral Abstract Session: Potpourri of Pediatric Infections
Thursday, October 3, 2013: 11:45 AM
Room: The Moscone Center: 250-262
Background: Topical antimicrobial and antiseptic agents are commonly used in the management of minor skin and soft tissue infections (SSTI).  Resistance to mupirocin has been documented in S. aureus isolates causing pediatric SSTIs.  Data are limited on the prevalence of retapamulin resistance or tolerance to antiseptics among SSTI isolates.  We sought to determine the prevalence of decreased susceptibility to retapamulin, mupirocin and chlorhexidine of S. aureus isolates from community-acquired SSTIs in children.

Methods: Isolates were selected from a prospective S. aureus surveillance study.  Two-hundred isolates from patients with a single SSTI and 200 isolates from patients with ≥3 previous episodes from the years 2010-2012 were selected for inclusion.  Screening for retapamulin resistance was performed by the macrobroth dilution method; mupirocin and linezolid MICs were determined by E-test.  PCR was performed for the presence of the chlorhexidine tolerance gene qacA/B. This study was supported by Stiefel, Inc.

Results: Among the 400 isolates, 269 were methicillin-resistant S. aureus (MRSA, 67.3%); 14.3% were clindamycin resistant.  Among those screened, 45 isolates (11.3%) exhibited retapamulin resistance.  28/45 (62.2%) retapamulin-resistant isolates were MRSA; all were SCC mec type IV.   Three isolates (0.7%) displayed cross-resistance to retapamulin and linezolid.  Thirty-nine isolates (9.8%) were found to have mupirocin resistance; nine isolates displayed cross-resistance to retapamulin.  The proportion of retapamulin and mupirocin resistant isolates increased significantly with the number of SSTIs.  qacA/B-positive S. aureus accounted for 14% of isolates.  The proportion of retapamulin and mupirocin resistance was stable during the study period while the proportion of qacA/B-positive organisms increased (p=0.005).

Conclusion: There is a high prevalence of in vitro resistance to topical antimicrobials among S. aureus causing SSTI in healthy children.  Retapamulin resistance was associated with cross resistance to mupirocin or linezolid in 2.2% and 0.7% of isolates, respectively.  In addition, there was a dramatic increase in the proportion of isolates with genotypic tolerance to antiseptics.  Further research involving clinical correlations with these findings is warranted.

Jonathon Mcneil, MD1, Kristina G. Hulten, PhD2, Sheldon L. Kaplan, MD, FIDSA2 and Edward Mason Jr, PhD3, (1)Department of Pediatrics, Baylor College of Medicine, Houston, TX, (2)Baylor College of Medicine and Texas Children's Hospital, Houston, TX, (3)Baylor College of Medicine, Houston, TX


J. Mcneil, Stiefel, Inc.: Grant Investigator, Research support

K. G. Hulten, None

S. L. Kaplan, None

E. Mason Jr, Stiefel, Inc.: Co-investigator, investigator initiated study, Research support

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