Thesis (M.Sc.) - Cairo University - Faculty of Medicine - Department of Microbiology and Immunology

The genus Pseudomonas consists of a group of medically important bacteria that are inhabitants of a wide range of niches including water and hospital environments. Improper use of disinfectants leads to appearance of resistance mechanisms to antibiotics. The aim of this study was to assess the effect of exposure of antibiotic susceptible pseudomonas isolates to sublethal concentrations of two disinfectants: didecyldimonium chloride (Virusolve+concentrate) and sodium hypochlorite (Chlorox 5.25%) on their antibiotic susceptibility pattern. This study involved 50 pseudomonas isolates collected from Kasr Alainy hospitals laboratories. Antibiotic susceptibility pattern of the isolates was assessed using disk diffusion and broth microdilution methods. The minimal inhibitory concentrations (MICs) of each antibiotic were compared before and after exposure to sublethal concentrations of virusolve+concentrate and Chlorox 5.25%. There was a statistically significant increase in the MICs of colistin (P=0.012), ceftazidime (P<0.001), amikacin (P<0.001), meropenem (P<0.001), gentamicin (P<0.001), piperacillin-tazobactam (P=0.003) and ciprofloxacin (P=0.004) after 24-hour incubation with sublethal concentration of clorox, whereas exposure to sublethal concentration of virusolve + showed a statistically significant increase in MICs of amikacin (P=<0.001), gentamicin (P<0.001), meropenem (P=0.041), and ciprofloxacin (P=0.008). The results of this study suggest that the standard disinfection policy using the recommended concentrations of disinfectants should be strictly followed in hospitals to avoid the emergence of drug resistant strains of bacteria

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