Biocide susceptibility in Staphylococcus epidermidis causing infection in pets

Abstract

Aim: To characterize biocide susceptibility of Staphylococcus epidermidis isolates causing infection in pets and evaluate proposed biocide epidemiological cut-off (tentative ECOFF) values. Methods: The study comprised a collection of 17 S. epidermidis isolates collected from several infection sources in cats and dogs from 2001 to 2016. Susceptibility to benzalkonium chloride (BAC), cetrim-ide, chlorhexidine digluconate, tetraphenylphosphonium bromide (TPP), triclosan (TCL) and ethidium bromide (EtBr) was evaluated by microdilution MIC determination. The efflux pump genes qacA/B, qacG, qacJ and smr, associated with biocide resistance, and the triclosan resistance gene sh-fabI were screened by PCR.Results: The MIC distributions for all biocides and EtBr were analyzed against the tentative ECOFF val-ues proposed for these compounds (see other poster by Costa et al, ISSSI 2018). Non-wild-type (NWT) populations were detected towards BAC (6/17), TPP (8/17) and TCL (4/17) and EtBr (9/17). The NWT populations towards BAC, TPP and EtBr were associated with the presence of either qacA or smr plas-mid-encoded genes, whereas the TCL NWT population was linked to sh-fabI carriage. One isolate carry-ing the smr gene was only detected taking into consideration the proposed EtBr ECOFF.Conclusion: This study illustrates the frequently reduced susceptibility towards relevant biocides of S. epidermidis infecting pets. It also supports the tentative ECOFF values suggested for BAC, TPP and TCL, as criteria to detect S. epidermidis harboring biocide resistance genes. The establishment of such crite-ria would enable early detection of S. epidermidis isolates with a non-wild-type phenotype and improve therapeutics in veterinary medicine.