Infiltration of hidden antimicrobial resistance among healthy people in a Japanese community.

BACKGROUND

Under non-antimicrobial selective pressure, antimicrobial-resistant bacteria do not easily become dominant in the microbiota. Furthermore, their low levels prevent detection by isolation, resulting in an underestimation of the prevalence of antimicrobial-resistant bacteria.

OBJECTIVES

We evaluated the infiltration of antimicrobial-resistant bacteria and their related β-lactamase genes among healthy people in non-clinical settings.

METHODS

Cephalosporin- and fluoroquinolone-resistant and genes were quantified in 217 faecal samples from healthy people in non-clinical settings in Japan. colonies grown on deoxycholate hydrogen sulphide-lactose (DHL) agar, with and without antimicrobials (cefotaxime and ciprofloxacin), were quantified, and isolates were analysed for their susceptibility to antimicrobials and the presence of genes. DNA extracted from faecal samples was used to quantify genes using quantitative PCR (qPCR).

RESULTS

The isolation rates of cefotaxime- and ciprofloxacin-resistant were 6.9% and 12.4%, respectively, using agars without antimicrobials, and 12.0% and 24.4%, respectively, using agars with antimicrobials. For samples from which cefotaxime- and ciprofloxacin-resistant were isolated only using agars with antimicrobials, the ratios of cfu on DHL agars with and without antimicrobials were below -2 log. harbouring genes were isolated from 35.0% of the faecal samples using agars, and genes were detected in 65.0% of faecal DNA samples using qPCR.

CONCLUSIONS

Among people carrying cefotaxime- and ciprofloxacin-resistant in non-clinical settings, cefotaxime- and ciprofloxacin-resistant were not dominant in half of the subjects. These individuals may play a role as reservoirs of antimicrobial-resistant bacteria.