Nosocomial , , , and : Sensitivity to Chlorhexidine-Based Biocides and Prevalence of Efflux Pump Genes.

The widespread use of disinfectants and antiseptics has led to the emergence of nosocomial pathogens that are less sensitive to these agents, which in combination with multidrug resistance (MDR) can pose a significant epidemiologic risk. We investigated the susceptibility of nosocomial , , , and to a 0.05% chlorhexidine (CHX) solution and a biocidal S7 composite solution based on CHX (0.07%) and benzalkonium chloride (BAC, 0.055%). The prevalence of efflux pump genes associated with biocide resistance and their relationship to antibiotic resistance was also determined. Both biocides were more effective against Gram-positive than Gram-negative bacteria. The most resistant strains were strains, which were mainly killed by 0.0016% CHX and by 0.0000084% (CHX)/0.0000066% (BAC) S7. The S7 bactericidal effect was observed on and after 10 min, while the bactericidal effect of CHX was only observed after 30 min. and efflux pump genes were prevalent among and , while was more often detected in . , , , , and were prevalent in . The observed prevalence of efflux pump genes highlights the potential problem whereby the sensitivity of bacteria to biocides could decline rapidly in the future.