Biocide’s susceptibility and frequency of biocide resistance genes and the effect of exposure to sub-inhibitory concentrations of sodium hypochlorite on antibiotic susceptibility of Stenotrophomonas maltophilia

The overuse of biocides in healthcare-facilities poses risk for emergence and spread of antibiotic resistance among nosocomial pathogens. Hospital-acquired infections due to S. maltophilia have been increased. The objective of this study was to evaluate the susceptibility of S. maltophilia clinical isolates to commonly used biocides in hospitals, as well asthe frequency of biocides resistance genes among them. This study also intended to assess the effect of exposureof S. maltophilia isolates to sub-inhibitory concentrations of sodium hypochlorite upon the antimicrobial susceptibility patterns.This study included 97 S.maltophilia isolates.Biofilm formation was determined by microtiter plate assay. The susceptibility tests of five biocides were studied against all S. maltophilia isolates by microbroth dilution method. Susceptibility of isolates to antibiotics by disk diffusion method were compared before and after exposure to sub-inhibitory concentrations of sodium hypochlorite. Presence of qacE, qacE Δ 1, SugE genes was screened by PCR. Based on minimum inhibitory and bactericidal concentrations of biocidessodium hypochlorite 5% and ethyl alcohol 70% were the strongest and weakest against S. maltophilia isolates, respectively. The frequency of sugE gene resistance genes was found 90.7% in our clinical S. maltophilia isolates. None of the isolates carried qacE and qacEΔ1 gene. Exposure to sub-inhibitory concentration of sodium hypochlorite showed significantly change the susceptibility of isolates towards ceftazidime ( P = .019), ticarcillin/clavulanate ( P = .009), and chloramphenicol ( P = .028).This study demonstrated that exposure to sub-inhibitory concentrations of sodium hypochlorite leads to reduced antibiotic susceptibility and development of multidrug-resistant S.maltophilia strains.