title: Clinical and Molecular Features of Decreased Chlorhexidine Susceptibility among Nosocomial Staphylococcus aureus Isolates at Texas Children's Hospital.
abstract: One 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 nosocomial Staphylococcus aureus isolates from 2007 to 2013 for the presence of genes associated with tolerance to chlorhexidine. Isolates and patients were identified from an S. aureus surveillance study at Texas Children's Hospital. Nosocomial S. aureus isolates (those causing infection at ≥72 h of hospitalization) were identified and underwent PCR for the qacA or qacB (qacA/B) and smr genes associated with elevated minimum bactericidal concentrations of chlorhexidine. Molecular typing with pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and agr typing and a review of the medical record were performed. Two hundred forty-seven nosocomial S. aureus infections were identified. Overall, 111 isolates carried one or both genes (44.9%); 33.1% were positive for smr, 22.7% were positive for qacA/B, and 10.9% of the isolates possessed both genes. The smr-positive isolates were more often resistant to methicillin, ciprofloxacin, and/or clindamycin. The isolates positive for qacA/B were more often associated with indwelling central venous catheters and a vancomycin MIC of ≥2 μg/ml. Isolates carrying either smr or qacA/B were associated with a diagnosis of bacteremia. The smr-positive isolates more often belonged to sequence type 8 (ST8) than the isolates that were positive for qacA/B. Mupirocin resistance was detected in 2.8% of the isolates. Antiseptic-tolerant S. aureus strains 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.
authors.affiliation: Department of Pediatrics, Section of Infectious Diseases, Baylor College of Medicine, Houston, Texas, USA jm140109@bcm.tmc.edu.
authors.forename: J Chase
authors.initials: JC
authors.lastname: McNeil
authors.affiliation: Department of Pediatrics, Section of Infectious Diseases, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Eric Y
authors.initials: EY
authors.lastname: Kok
authors.affiliation: Department of Pediatrics, Section of Infectious Diseases, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Jesus G
authors.initials: JG
authors.lastname: Vallejo
authors.affiliation: Department of Pediatrics, Section of Infectious Diseases, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Judith R
authors.initials: JR
authors.lastname: Campbell
authors.affiliation: Department of Pediatrics, Section of Infectious Diseases, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Kristina G
authors.initials: KG
authors.lastname: Hulten
authors.affiliation: Department of Pediatrics, Section of Infectious Diseases, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Edward O
authors.initials: EO
authors.lastname: Mason
authors.affiliation: Department of Pediatrics, Section of Infectious Diseases, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Sheldon L
authors.initials: SL
authors.lastname: Kaplan
mesh_terms: D000293:Adolescent; D000328:Adult; D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D002710:Chlorhexidine / Q000494:pharmacology*; D003428:Cross Infection / Q000382:microbiology* / Q000517:prevention & control; D024881:Drug Resistance, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D006801:Humans; D007223:Infant; D017053:Infection Control; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D058885:Multilocus Sequence Typing; D016712:Mupirocin / Q000494:pharmacology; D013203:Staphylococcal Infections / Q000382:microbiology* / Q000517:prevention & control; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D013781:Texas; D055815:Young Adult
chemical_list: D000891:Anti-Infective Agents, Local; D016712:Mupirocin; D002710:Chlorhexidine