Prevalence of Metallo-β-lactamases Encoding Genes Among Pseudomonas aeruginosa Strains Isolated From the Bedridden Patients in the Intensive Care Units

Background: Pseudomonas aeruginosa is one of the most important agents causing nosocomial infections worldwide. Multidrug resistance of isolated bacteria from nosocomial infections makes it difficult and sometimes impossible to treat. Objectives: The aim of the present study was to investigate the antibiotic resistance and association between blaIMP and blaVIM genes with resistance to meropenem and imipenem among P. aeruginosa strains isolated from Iranian patients in ICU wards of Hamadan, IR Iran. Patients and Methods: In this cross-sectional study, ۱۰۰ P. aeruginosa strains were isolated from bedridden patients in ICU wards of three university hospitals during five months in ۲۰۱۲. Isolates were confirmed at species level using biochemical tests. Their susceptibility to ۱۸ antibiotics was assessed using Kirby-Bauer disc diffusion method. The minimum inhibitory concentration (MIC) was determined by E-test method. Single PCR was used for detecting blaVIM, and blaIMP genes. Results: The highest resistance rates of the isolates to ampicillin/sulbactam, tigecycline, and cefotaxime were ۹۵%, ۷۶%, and ۶۷%, respectively. The lowest resistance rates were observed by colistin sulfate (۹۶%), piperacillin/tazobactam (۸۱%), amikacin (۷۷%), aztreonam (۷۷%), meropenem (۷۶%), imipenem (۷۶%), cefepime (۷۶%), piperacillin (۷۴%), ceftazidime (۷۴%), gentamycin (۷۲%), tobramycin (۷۳%), and levofloxacin (۷۰%) . E-test illustrated that ۲۴% of the isolates were resistant to imipenem (MIC: ۳۲ µg/mL). In contrary to blaVIM gene that was not detected in any isolate, blaIMP gene was detected in ۴% of the isolates. No statistically significant association was observed between resistance rates to imipenem and meropenem with aforementioned genes. Conclusions: Prevalence of P. aeruginosa strains drug resistance in our areas was very high and alerting, but the other antibiotics were effective enough to be used in treatment of the infection. Overall, low resistance rate in this region was probably resulted from low prevalence of metallo-β-lactamases producing strains. Permanent monitoring of changes in P. aeruginosa resistance would help to determine national priorities for local intervention efforts.