Potential public health impact of the development of antimicrobial resistance in clinical isolates of Pseudomonas aeruginosa on repeated exposure to biocides In vitro

Abstract

Background: Antimicrobial resistance (AMR) is a real threat having the potential of impacting public health immensely. Biocides may contribute to AMR as they are routinely used in household formulations, often in suboptimal concentrations. Gram-negative bacteria like Pseudomonas aeruginosa (P. aeruginosa) can adapt to biocides such as chlorhexidine and cetrimide (CHX + CET) on repeated exposure and develop cross-resistance to antibiotics. Aim and Objective: The aim was to test CHX + CET laboratory-adapted clinical isolates of P. aeruginosa for the development of cross-resistance to antipseudomonal antibiotics. Materials and Methods: Ten clinical isolates of P. aeruginosa were included in the study. The initial antibiotic susceptibility pattern was noted before they were exposed to increasing concentrations of CHX + CET over several days. Briefly, 10 μl of bacterial suspension was inoculated into 10 ml of nutrient broth with the biocide and incubated at 37°C for 48 h. New series of tubes with increasing concentration of biocide were inoculated with growth from the previous tube every 48 h. Till, no further growth was obtained. Antibiotic susceptibility testing for antipseudomonal antibiotics by the disc diffusion as well as the minimum inhibitory concentration (MIC) by VITEK 2 bacterial identification system was performed and repeated before and after exposure to the biocide. The difference in the zone diameter and MIC was noted. Results: Significant difference (P < 0.05) in the mean of the zone size before and after exposure to CHX + CET was noted. Furthermore, there was an increase in MIC postexposure to the biocide. Conclusions: P. aeruginosa on exposure to biocides developed antibiotic resistance.

Keywords

• antimicrobial resistance
• biocides
• chlorhexidine
• pseudomonas aeruginosa