Prevalence of Extended-Spectrum
-Lactamase class A among Acinetobacter baumannii isolates from patients of Imam Reza hospital, Tabriz

Resistance patterns among nosocomial bacterial pathogens in hospitals may vary in different part of the world. Acinetobacter (A.) baumannii is one of the most important nosocomial pathogens particularly in intensivecare- units. Production of extended-spectrum beta-lactamases (ESBL) is one of the main resistance mechanisms against new cephalosporins in A. baumannii. Therefore, surveillance of antibiotic resistance pattern of A. baumannii is necessary for infection control programs. In this study, a total of 100 clinical isolates A. baumannii were collected from patients hospitalized in Imam Reza hospital of Tabriz city. The isolates were identified using standard biochemical tests and antibiotic susceptibility was determined by the disk diffusion method. The double disk synergy test was used for detection of ESBL production among the isolates. Prevalence of ESBLs class A was determined by PCR technique. Results of antimicrobial susceptibility testing showed that the lowest resistance rate was against polymixin B (16%) and colistin (19%) whereas the highest resistance rate was observed against Ticarcillin (100%), Cefiexim (100%) and Ceftizoxim (100%). PCR results showed that among 60 ESBL positive A. baumannii isolates, ESBLs class A was responsible for 56% of ESBLs. A high frequency of ESBL production was seen among studied A. baumannii isolates where the SHV genotype was the most common ESBL type.