Impact of Health Care Exposure on Genotypic Antiseptic Tolerance in Staphylococcus aureus Infections in a Pediatric Population

Abstract

Staphylococcus aureus possessing either the smr gene or the qacA/B genes is associated with decreased susceptibility to chlorhexidine gluconate (CHG) and other antiseptics. Previous studies of antiseptic-tolerant staphylococci have focused largely on high-risk populations, and the exact role of health care exposure in the acquisition of these organisms is unclear. We sought to describe the risk factors and features of infection caused by antiseptic-tolerant S. aureus in a general pediatric population. Isolates were selected from an ongoing S. aureus surveillance study. Every third sequential isolate in the year 2014 was selected for inclusion. All isolates underwent PCR for the genes qacA/B and smr. Medical records were reviewed. Five hundred six isolates were included in the study, with 377 (74.3%) being community acquired. One hundred (19.8%) isolates were smr positive and 79 (15.6%) qacA/B positive. In univariable analyses, the presence of either gene was associated with underlying medical conditions, nosocomial acquisition, recent hospitalization, central venous lines, and CHG exposure. In multivariable analyses, only differences between patients with chronic medical conditions (odds ratio [OR] ϭ 1.72; 95% confidence interval [CI], 1.22 to 2.64) and nosocomial acquisition (OR ϭ 2.48; 95% CI, 1.16 to 8.17) remained statistically significant. Among patients without risk factors, 27.9% had infection with an antiseptic-tolerant isolate. smr-or qacA/B-positive S. aureus isolates are common in children and are independently associated with nosocomial acquisition and underlying medical conditions. These findings imply a role for the health care environment in acquisition of these organisms. However, genotypic antiseptic tolerance was seen in Ͼ25% of healthy children with an S. aureus infection, indicating that these organism are prevalent in the community as well.

Clinical and Molecular Characteristics of qacA - and qacB -Positive Methicillin-Resistant Staphylococcus aureus Causing Bloodstream Infections

“…In the present study, patients infected with qacA-and qacB-positive MRSA had common risk factors for health care-associated infections, including prior antibiotic use, central venous catheter in situ, ICU-acquired bacteremia, and nosocomial infection. These findings are consistent with previous studies revealing an association between the presence of qacA and qacB and health care exposure and provide evidence that the widespread use of CHG in hospital settings selects for genotypic chlorhexidine-tolerant strains that are able to survive in the presence of this antiseptic (14,19,23). In addition, as several previous studies have reported, we also found an association between chlorhexidine tolerance genes and resistance to non-␤-lactam antibiotics and a higher chlorhexidine MIC (11,14,23).…”

“…These findings are consistent with previous studies revealing an association between the presence of qacA and qacB and health care exposure and provide evidence that the widespread use of CHG in hospital settings selects for genotypic chlorhexidine-tolerant strains that are able to survive in the presence of this antiseptic (14,19,23). In addition, as several previous studies have reported, we also found an association between chlorhexidine tolerance genes and resistance to non-␤-lactam antibiotics and a higher chlorhexidine MIC (11,14,23). Although prior antibiotic use was independently associated with qacA-and qacB-positive MRSA in the present study, we could not determine whether there was antibiotic pressure on the selection of these microorganisms or whether this finding was simply a reflection of the coexistence of antimicrobial resistance genes on mobile genetic elements (24).…”

“…Another study reported that qacA and qacB genes in combination with low-level mupirocin resistance was related to failure of MRSA decolonization (13). Although a recent study reported that health care exposure, specifically nosocomial S. aureus acquisition and underlying medical conditions, was associated with chlorhexidine tolerance genes, factors predictive of the presence of qacA and qacB genes have not been well described (14). In the present study, we investigated the molecular epidemiology of qacA-and qacB-positive MRSA in bloodstream infection (BSI) isolates, and we describe the clinical significance of these isolates.…”

The prevalence of antiseptic tolerance genes among staphylococci and enterococci in a pediatric population

“…20,[22][23][24] Pediatric-specific data are of relevance given the variable use of CHG in children's hospitals, particularly in neonatal intensive care units (NICUs), arising from concerns for systemic absorption and safety in young children. 25,26 We have reported that among a random sample of S. aureus isolates at Texas Children's Hospital (TCH), 32.8% possessed either smr or qacA/B, 21 suggesting our center represents a high prevalence region for AT.…”

“…[17][18][19][20] In a recent study by our group, the presence of genotypic AT in S. aureus was independently associated with chronic medical comorbidities in the host and nosocomial acquisition of infection. 21 The relative prevalence of these genes among S. aureus in pediatric populations varies widely, ranging from 1% to 44.5% depending on geographic location and the type of patients studied. 20,[22][23][24] Pediatric-specific data are of relevance given the variable use of CHG in children's hospitals, particularly in neonatal intensive care units (NICUs), arising from concerns for systemic absorption and safety in young children.…”