TY - JOUR
T1 - A novel, widespread qacA allele results in reduced chlorhexidine susceptibility in staphylococcus epidermidis
AU - Addetia, Amin
AU - Greninger, Alexander L.
AU - Adler, Amanda
AU - Yuan, Shuhua
AU - Makhsous, Negar
AU - Qin, Xuan
AU - Zerr, Danielle M.
N1 - Funding Information:
This work was supported by the National Cancer Institute at the National Institutes of Health (R01CA163394 and UG1CA189955). The research was also supported by St. Baldrick’s Foundation.
Publisher Copyright:
Copyright © 2019 American Society for Microbiology. All Rights Reserved.
PY - 2019/6
Y1 - 2019/6
N2 - Chlorhexidine gluconate (CHG) is a topical antiseptic widely used in health care settings. In Staphylococcus spp., the pump QacA effluxes CHG, while the closely related QacB cannot due to a single amino acid substitution. We characterized 1,050 cutaneous Staphylococcus isolates obtained from 173 pediatric oncology patients enrolled in a multicenter CHG bathing trial. CHG susceptibility testing revealed that 63 (6%) of these isolates had elevated CHG MICs (4 g/ml). Screening of all 1,050 isolates for the qacA/B gene (the same qac gene with A or B allele) by restriction fragment length polymorphism (RFLP) yielded 56 isolates with a novel qacA/B RFLP pattern, qacA/B273. The CHG MIC was significantly higher for qacA/B273positive isolates (MIC50, 4 g/ml; MIC range, 0.5 to 4 g/ml) than for other qac groups: qacA-positive isolates (n 559; MIC50, 1 g/ml; MIC range, 0.5 to 4 g/ml), qacB-positive isolates (n 17; MIC50, 1 g/ml; MIC range, 0.25 to 2 g/ml), and qacA/ B-negative isolates (n 418, MIC50, 1 g/ml; MIC range, 0.125 to 2 g/ml) (P 0.001). A high proportion of the qacA/B273-positive isolates also displayed methicillin resistance (96.4%) compared to the other qac groups (24.9 to 61.7%) (P 0.001). Whole-genome sequencing revealed that qacA/B273-positive isolates encoded a variant of QacA with 2 amino acid substitutions. This new allele, named qacA4, was carried on the novel plasmid pAQZ1. The qacA4-carrying isolates belonged to the highly resistant Staphylococcus epidermidis sequence type 2 clone. By searching available sequence data sets, we identified 39 additional qacA4-carrying S. epidermidis strains from 5 countries. Curing an isolate of qacA4 resulted in a 4-fold decrease in the CHG MIC, confirming the role of qacA4 in the elevated CHG MIC. Our results highlight the importance of further studying qacA4 and its functional role in clinical staphylococci.
AB - Chlorhexidine gluconate (CHG) is a topical antiseptic widely used in health care settings. In Staphylococcus spp., the pump QacA effluxes CHG, while the closely related QacB cannot due to a single amino acid substitution. We characterized 1,050 cutaneous Staphylococcus isolates obtained from 173 pediatric oncology patients enrolled in a multicenter CHG bathing trial. CHG susceptibility testing revealed that 63 (6%) of these isolates had elevated CHG MICs (4 g/ml). Screening of all 1,050 isolates for the qacA/B gene (the same qac gene with A or B allele) by restriction fragment length polymorphism (RFLP) yielded 56 isolates with a novel qacA/B RFLP pattern, qacA/B273. The CHG MIC was significantly higher for qacA/B273positive isolates (MIC50, 4 g/ml; MIC range, 0.5 to 4 g/ml) than for other qac groups: qacA-positive isolates (n 559; MIC50, 1 g/ml; MIC range, 0.5 to 4 g/ml), qacB-positive isolates (n 17; MIC50, 1 g/ml; MIC range, 0.25 to 2 g/ml), and qacA/ B-negative isolates (n 418, MIC50, 1 g/ml; MIC range, 0.125 to 2 g/ml) (P 0.001). A high proportion of the qacA/B273-positive isolates also displayed methicillin resistance (96.4%) compared to the other qac groups (24.9 to 61.7%) (P 0.001). Whole-genome sequencing revealed that qacA/B273-positive isolates encoded a variant of QacA with 2 amino acid substitutions. This new allele, named qacA4, was carried on the novel plasmid pAQZ1. The qacA4-carrying isolates belonged to the highly resistant Staphylococcus epidermidis sequence type 2 clone. By searching available sequence data sets, we identified 39 additional qacA4-carrying S. epidermidis strains from 5 countries. Curing an isolate of qacA4 resulted in a 4-fold decrease in the CHG MIC, confirming the role of qacA4 in the elevated CHG MIC. Our results highlight the importance of further studying qacA4 and its functional role in clinical staphylococci.
KW - CHG
KW - Chlorhexidine
KW - Chlorhexidine gluconate
KW - Coagulase-negative staphylococci
KW - QacA
KW - QacA/B
KW - QacB
KW - Staphylococcus
KW - Staphylococcus epidermidis
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U2 - 10.1128/AAC.02607-18
DO - 10.1128/AAC.02607-18
M3 - Article
C2 - 30988144
AN - SCOPUS:85066431111
SN - 0066-4804
VL - 63
JO - Antimicrobial agents and chemotherapy
JF - Antimicrobial agents and chemotherapy
IS - 6
M1 - e02607-18
ER -