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.