Biocide efficacy against extensively drug-resistant (XDR) Pseudomonas aeruginosa patient isolates during planktonic and biofilm growth.

BACKGROUND

Pseudomonas aeruginosa is a major cause of hospital-acquired infections and presents a growing threat due to the emergence of extensively drug-resistant (XDR) strains. In addition to antibiotic resistance, they can survive exposure to hospital disinfectants, particularly when embedded in biofilms. We hypothesized that XDR P aeruginosa strains exhibit increased tolerance to hospital disinfectants in both planktonic and biofilm states.

METHODS

We evaluated the susceptibility of XDR P aeruginosa isolates to sodium hypochlorite, ethanol, 4 commercial hospital disinfectants, and chlorhexidine gluconate (CHG). Minimum inhibitory concentrations and minimum bactericidal concentrations were determined by broth microdilution and time-kill assays.

RESULTS

All disinfectants eliminated > 99.9% of planktonic bacteria, except 0.63% sodium hypochlorite, where a small subpopulation persisted. In contrast, biofilms exposed to sodium hypochlorite showed 55% to 90% survival after 4 minutes, while exposure to disinfectant wipes and CHG resulted in < 9% survival at all time points. All strains demonstrated decreased susceptibility to sodium hypochlorite when present in biofilms.

DISCUSSION AND

CONCLUSIONS

Our results highlight differences in disinfectant and CHG performance between planktonic and biofilm associated bacteria under laboratory conditions and underscore the importance of considering biofilm-associated organisms when interpreting disinfectant efficacy data.