The study of influence of some physicochemical agents in resistance pattern of Escherichia coli and Pseudomonas aeruginosa

Introduction and objective: Nowadays the microbial resistance to antibiotics and other physicochemical agents has caused various problems in the process of disinfecting devices and surfaces of the hospitals and in treatment of the patients. Thus, the aim of this study has been to examine resistance patterns of some penicillin resistant bacteria to physiochemical agents (UV and gamma radiation, cetrimide, and some of heavy metals).

Materials and methods: In the present study, strains of penicillin resistant bacteria isolated from Alzahra hospital of Esfahan, including 39 strains of Escherichia coli and 23 strains of Pseudomonas aeruginosa were studied. To screen for cetrimide and cadmium, mercury and arsenate resistance was measured using micro titer plates, steer‘s replicator and serial dilution for determining minimal inhibitory concentration (MIC).

Results: The most MIC determined in E. coli and P. aeruginosa strains respectively were 50 and 400mg/ml (Cd and Hg). MIC of metals was determined in adaptation condition for some of resistant bacteria. Results showed that in the most cases bacteria were selected and radiated with intensity of 0.25J/m²s. Mean of cfu/0.1ml after 240s radiation in E. coli and P. aeruginosa were, respectively 4.7 and 3.6. Gamma radiation was performed with intensity of 20Gray /min (GY/min) in different times in these resistance bacteria. Mean of cfu/ml for E. coli and P. aeruginosa strains in 1000Gray dose were, respectively 2.4×10² and 8.2×10².

Conclusion: Pseudomonas aeruginosa strains showed higher resistance than E. coli. But there was no significant difference in MIC of arsenate between these bacteria.

Significance and impact of the study: The impact of this study is to find E. coli and P. aeruginosa strains that are multi resistant to physicochemical agents; and to suggest a solution for destroying these specific strains.