Tolerance to disinfectants (chlorhexidine and isopropanol) and its association with antibiotic resistance in clinically-related isolates.

Disinfectants play an essential role in controlling the dissemination of bacteria in health care settings, but it may also contribute to the selection of antibiotic resistance bacteria. This study looked at isolates collected from three hospitals in Lima, Peru, in order to evaluate: their susceptibility to chlorhexidine [CHG] and isopropanol [ISP]), and their association with antimicrobial susceptibility. We analyzed 59  isolates and assessed their CHG and ISP susceptibility by minimum inhibitory concentrations (MICs). Additionally, we performed a regression analysis to assess the association between disinfectant tolerance and antibiotic resistance (measured by the disc diffusion method), colistin resistance (by microdilution), carbapenemases presence (by polymerase chain reaction [PCR]), and clonal relationships (by pulsed-field gel electrophoresis [PFGE]). Eleven strains were isolated from fomites, and 48 strains from clinical samples. The MIC range of these isolates was 8-128 µg/ml for CHG and 16-256 mg/ml for ISP. We found that resistance to trimethoprim/sulfamethoxazole (TMP/SMX) was the main factor associated with CHG log MIC (ß = 0.65; 95%CI: 0.03, 1.27; R = 0.07). In the case of ISP, the log(MIC) was associated with the institution of origin, showing lower ISP log(MIC) in fomites compared to clinical samples(ß = -0.77; 95%CI: -1.54, -0.01; R = 0.08). Resistance to CHG and ISP among isolates found in Peruvian hospitals seems to be elevated and highly variable. Further studies are needed to confirm our results and implement actionable interventions if necessary.