Systematic Analysis of Efflux Pump-Mediated Antiseptic Resistance in Staphylococcus aureus Suggests a Need for Greater Antiseptic Stewardship

Abstract

Staphylococcus aureus-associated infections can be difficult to treat due to multidrug resistance. Thus, infection prevention is critical. Cationic antiseptics, such as chlorhexidine (CHX) and benzalkonium chloride (BKC), are liberally used in health care and community settings to prevent infection. However, increased administration of antiseptics has selected for S. aureus strains that show reduced susceptibilities to cationic antiseptics. This increased resistance has been associated with carriage of specific efflux pumps (QacA, QacC, and NorA). Since prior published studies focused on different strains and on strains carrying only a single efflux gene, the relative importance of these various systems to antiseptic resistance is difficult to ascertain. To overcome this, we engineered a collection of isogenic S. aureus strains that harbored norA, qacA, and qacC, individually or in combination. MIC assays showed that qacA was associated with increased resistance to CHX, cetrimide (CT), and BKC, qacC was associated with resistance to CT and BKC, and norA was necessary for basal-level resistance to the majority of tested antiseptics. When all three pumps were present in a single strain, an additive effect was observed in the MIC for CT. Transcriptional analysis revealed that expression of qacA and norA was significantly induced following exposure to BKC. Alarmingly, in a strain carrying qacA and norA, preexposure to BKC increased CHX tolerance. Overall, our results reveal increased antiseptic resistance in strains carrying multiple efflux pumps and indicate that preexposure to BKC, which is found in numerous daily-use products, can increase CHX tolerance. IMPORTANCE S. aureus remains a significant cause of disease within hospitals and communities. To reduce the burden of S. aureus infections, antiseptics are ubiquitously used in our daily lives. Furthermore, many antiseptic compounds are dual purpose and are found in household products. The increased abundance of antiseptic compounds has selected for S. aureus strains that carry efflux pumps that increase resistance to antiseptic compounds; however, the effect of carrying multiple pumps within S. aureus is unclear. We demonstrated that an isogenic strain carrying multiple efflux pumps had an additive resistance phenotype to cetrimide. Moreover, in a strain carrying qacA and norA, increased chlorhexidine tolerance was observed after the strain was preexposed to subinhibitory concentrations of a different common-use antiseptic. Taken together, our findings demonstrate cooperation between antiseptic resistance efflux pumps and suggest that their protective phenotype may be exacerbated by priming with subinhibitory concentrations of household antiseptics.

Cetylpyridinium Chloride: Mechanism of Action, Antimicrobial Efficacy in Biofilms, and Potential Risks of Resistance

“…Currently, there is still poor understanding of whether transcription of these genes can be affected by antiseptic exposure and, in turn, confer antibiotic resistance (72,77). In a recent study, LaBreck et al showed that exposure to the QAC benzalkonium chloride induced a sustained 10-fold increase in qacA expression as well as a sustained 2-fold increase in norA expression in isogenic strains of S. aureus (77). Although suchlike effects have not been studied for CPC so far, it must be kept in mind that genetic determinants conferring resistance to antibiotics and antiseptics are often linked to each other and located on the same plasmids (72).…”

Persistence against benzalkonium chloride promotes rapid evolution of tolerance during periodic disinfection

“…Several studies showed examples of reduced susceptibilities to QACs, occurring in natural, clinical, and industrial isolates and, to a lesser extent, in laboratory evolution experiments 9 , 14 – 16 . Reduced susceptibility to QACs is underpinned by acquiring mutations in genes that increase QAC efflux by upregulation of inherent multidrug-efflux pumps 17 or by acquiring specialized QAC efflux pumps via horizontal gene transfer 18 , 19 . In addition, strains that have been evolved towards decreased susceptibility show reduced expression of porins related to reduced QAC uptake 20 , 21 and changes in membrane structure or composition 21 , 22 .…”

Antimicrobial and Antioxidative Activity of Newly Synthesized Peptides Absorbed into Bacterial Cellulose Carrier against Acne vulgaris

“…The application of a common antiseptic agent, chlorhexidine, may cause accidental or recurrent inflammatory and allergic reactions [ 48 ], while the use of polihexanide may display toxic effects to keratinocytes and lead to dermatitis in patients [ 49 ], and wound irrigation with octenidine dihydrochloride may result in severe complications, such as aseptic necrosis and chronic inflammation in penetrating hand wounds [ 50 ]. No such side effects were reported as a result of the studied peptide’s activities, and, additionally, increased microbial tolerance/reduced susceptibility towards chlorhexidine [ 51 ], octenidine [ 52 ] and polihexanide [ 53 ] has already been indicated.…”