P12 | Dissemination of biocide resistance genes in staphylococci isolated from the hands of collective catering workers: correlation with the antibiotic resistance profile

Purpose. The spread of microorganisms resistant to antibiotics and biocides is currently one of the main public health problems worldwide. With the COVID-19 pandemic, the use of chemicals for surface disinfection and hand sanitization has significantly intensified in various community settings, including collective catering, increasing selective pressure and consequently favoring the risk of the spread of resistant strains. The aim of this study was to evaluate the prevalence of the main genes involved in biocide tolerance mechanisms in various species of staphylococci, both coagulase-positive and negative, with different antibiotic resistance profiles, isolated from the hands of food service workers. Methods. A total of 176 strains of staphylococci isolated between 2021 and 2024 from swabs taken from the hands of food handlers preparing meals for children (school canteens) and the elderly (nursing home canteens) were analyzed. For all bacterial strains, the species was determined by mass spectrometry (MALDI-TOF) and the antimicrobial resistance profile (Kirby-Bauer method) was assessed using a panel of 13 molecules (amoxicillin/clavulanic acid, ampicillin, cefoxitin, cefotaxime, ciprofloxacin, clindamycin, erythromycin, gentamicin, imipenem, oxacillin, penicillin G, tetracycline, and trimethoprim/sulfamethoxazole). Genes for resistance to chemical disinfectants (qacA/B and qacC, which confer tolerance to chlorhexidine and quaternary ammonium compounds) were investigated using real-time PCR with SYBR Green chemistry, after bacterial DNA was extracted by boiling. Results. The 176 bacterial isolates analyzed were found to belong to different species of the genus Staphylococcus: 37.5% S. warneri, 25% S. epidermidis, 14.2% S. pasteuri, 9.66% S. haemolyticus, 5.68% S. hominis, 2.84% S. aureus, 2.27% S. lugdunensis, 1.14% S. capitis, 1.14% S. saprophyticus, and 0.57% S. xylosus. Most strains (75%) were resistant to at least one of the antibiotic molecules tested, with a higher frequency of resistance to penicillin (55.7%), followed by erythromycin (31.8%) and gentamicin (13.6%). 15.9% of the 176 bacterial isolates analyzed tested positive for the qacA/B gene, 35.2% for the qacC gene, and 0.6% tested positive for both genes tested. For staphylococci positive for the qacA/B gene, a higher frequency of resistance to various antibiotics was observed compared to negative isolates. This association, however, was less evident in the isolates positive for the qacC gene, where no significant differences in antibiotic resistance were recorded compared to the negative strains. Conclusions. The results obtained highlighted the spread of staphylococci carrying resistance genes to chemical disinfectants in the context of collective catering for vulnerable users (elderly and children). The presence of such genes, especially if located on mobile genetic elements like plasmids, poses a serious risk to public health due to the possibility of being easily transferred to other pathogenic bacteria and the potential existence of co-resistance phenomena to biocides and antibiotics.