Drug Susceptibility and Molecular Epidemiology of Pseudomonas aeruginosa Isolated in a Burn Unit

Problem statement: Pseudomonas aeruginosa is an opportunistic pathogen that still develops life-threatening infections in patients with immunological system defects, like burn patients, especially in developing countries. Since this bacterium is naturally resistant to many drugs and is able to get resistance to all effective antibiotics, the infection with this organism is particularly problematic condition for patients. This study was design to evaluated drug susceptibility for determination of multidrug-resistant isolates and molecular epidemiology of P. aeruginosa colonization for investigation of the isolates routes in the burn unit of Shahid Motahhari Hospital in Tehran. Approach: About 127 clinical and 2 environmental P. aeruginosa isolates were collected during 6 months. All P. aeruginosa isolates were analyzed for drug susceptibility by disk diffusion method and molecular epidemiology assessment were done by RAPD-PCR analysis. Results: Drug susceptibility tests were shown high resistance for ceftizoxime (86.8%), aztreonam (80.6%), kanamycin (79.8%) and tetracycline (78.3%); furthermore, low resistance for some antibiotics like imipenem (30.2%), piperacillin/tazobactam (34.1%) and amikacin (41.1%) was showed. In addition, 42 multidrug-resistant P. aeruginosa isolates were recovered from clinical specimens and one isolate from environmental samples. Molecular typing revealed eight different profiles that include two profiles, RAPD1 and RAPD4, with environmental resource. The major RAPD profile was RAPD1 profile (n = 64, 50.4%), which includes 31 (72.1%) multidrug-resistant isolates with an environmental reservoir. Conclusion: In summery, we were found three different profiles for multidrug-resistant strains. Different RAPD profiles suggested the different resources of infection, two environmental resources were found, that one of them was multidrug-resistant strain. These findings highlighted the need for further attention to disinfection inanimate hospital environment and controlled contact between staff with patients to limit transfer of P. aeruginosa in this BU; moreover, use of some antimicrobial agents must be restricted due to existence of high resistance and using of combined effective antibiotics is recommend.