Evaluation of temperature, drying time and other determinants for the recovery of Gram-negative bacterial pathogens in disinfectant efficacy testing.

ABSTRACT

BACKGROUND: In the clinical setting, surface disinfection is an important measure to reduce the risk of cross transmission of micro-organisms and the risk of nosocomial infections. Standardized methods can be used to evaluate disinfection procedures, as well as the effectiveness of the active ingredients used for disinfection. However, despite standardization, the results of such methodologies are still determined by several factors, and incorrect results may lead to invalid assumptions about the effectiveness of a disinfectant, posing significant health risks for patients and health personnel. AIM: The objective of this study was to evaluate several determinants for the recovery of Pseudomonas aeruginosa and other test organisms to establish their influence on the results of standardized disinfection methodologies, and to find Gram-negative strains that can be used as suitable replacements for P. aeruginosa. METHODS: The effects of inoculum application method, drying time, temperature and carrier material on the survival and recovery of the test organisms were evaluated using Student's t-test, one-way analysis of variance and Tukey's multiple comparison test. FINDINGS AND CONCLUSIONS: Temperature, drying time, application method and carrier material were found to affect the recovery of P. aeruginosa cells significantly, and therefore influence the outcome of the methodologies used. This study also showed thatP. aeruginosa could be replaced with the Gram-negative species Acinetobacter baumannii, a test organism used in many standardized methodologies, which responds better under the same circumstances and has a behaviour similar to that of P. aeruginosa in disinfectant efficacy tests.