Class A and D Extended-Spectrum β-Lactamases in Imipenem Resistant Pseudomonas aeruginosa Isolated From Burn Patients in Iran

BACKGROUND: Pseudomonas aeruginosa remains a leading cause of severe wound infection and mortality in burn patients. OBJECTIVES: The current study aimed to determine the prevalence of Ambler class A and D β-lactamases among P. aeruginosa isolated from infected burn injuries in Tehran, Iran. PATIENTS AND METHODS: Bacteriological samples were taken from burn patients with clinical symptoms of burn infection. Fifty Gram-negative, oxidase-positive, catalase- positive bacilli, grown at 42ºC and production of pigment on Mueller-Hinton agar were identified as P. aeruginosa. All of the 50 isolates were examined for antibiotic susceptibility via disk diffusion method, and production of Ambler class A and and D β-lactamases by phenotypic screening test. The presence of Ambler class A and D β-lactamases was confirmed by polymerase chain reaction technique. RESULTS: The results showed that the majority of isolates (88%) were multi-drug resistant. Out of these 50 imipenem resistant isolates, 7 (14%), 18 (36%), 18 (36%) and 18 (36%) strains were positive for bla(PER), bla(OXA-10), bla(TEM) and bla(SHV) genes alone or in combination, respectively. None of the isolates possessed bla(KPC) or bla(GES) genes. CONCLUSIONS: The current study highlights that the high level of resistance to many antibacterial agents and a gradual increase in the degree of PER, OXA-10, SHV and TEM ESBLs among the majority of imipenem resistant P. aeruginosa isolated from patients with burn infection is an enormous threat in burn centers in Iran.