ISMJ

Background: Extended-spectrum beta-lactamases (ESBLs) have emerged as important mechanism of resistance among enterobacteriaceae family. These ESBL positive strains are major problem in hospitalized patients. The goal of this study was the survey emergence of multi-drug resistant ESBL producing strains among enterobacteriaceae members isolated from patients blood samples using BACTEC 9240 automatic system in south of Iran.

Materials & Methods: In this cross-sectional study, 4825 blood samples were collected from hospitalized patients, and positive samples were detected by BACTEC automatic system. Positive blood cultures removed from BACTEC and subculture was performed on microbiological media including blood agar, chocolate agar and MacConkey agar. The isolates were identified based on biochemical tests embedded in the API-20E system. Susceptibility testing (disc diffusion) was performed according clinical and laboratory standards institute (CLSI, 2013) guidelines. Phenotypic detection of extended spectrum beta-lactamase producing isolates was performed by double disk synergy test (DDST).

Results: Total 1145 (24%) blood cultures were positive that among them 248 (21.5%) belonged to the enterobacteriaceae family. The most common isolates in this family were Escherichia coli (46.5%), Klebsiella spp. (28%), Enterobacter spp. (13.5%). Among enterobacteriaceae family, ampicillin was most effective drug against Salmonella isolates. Escherichia coli was the most common ESBL-producing isolate (58% of isolates were ESBL positive). Respectively, polymyxin B, colistin, imipenem were the most effective drugs against ESBL-positive Klebsiella strains. The ESBL-positive Enterobacter strains showed lowest resistance to imipenem (7.7%). All ESBL positive Serratia isolates were sensitive to chloramphenicol, co-trimoxazole and imipenem.

Conclusion: Results showed unfortunately betalactam antibiotics are not effective against more than 40% of bacteremia caused by Escherichia coli and Klebsiella and 39% bacteremia caused by Enterobacter. Multi drug resistance strains are increasing and treatment of infections causing by this isolates are major problem in Iran.