Materials and Methods: A study was carried out from Jan 2012 to Jan 2013 in a referral university hospital. All neonates who had diagnosed as sepsis were enrolled in this study. Blood cultures were processed using the automated BACTEC 9120 system. Antibiotic resistance and beta-lactamase production of bacterial isolates was tested. All patients were followed till discharge.

Results: One hundred three neonates with gestation age 36.7±3.2 weeks were enrolled in this study and 56 cases (54%) were boys. The most common isolated gram negative pathogens were Klebsiella pneumoniae, Acinetobacter species, and Pseudomonas aeruginosa. The rate for beta-lactamase production were 97.7% in Klebsiella pneumoniae , 81.3% in Acinetobacter, 85.7% in E. coli, 53.3% in Pseudomonas aeruginosa and 100% in Serratia. Thirty eight (35.9%) neonates were dead, that 34 of them were beta-lactamase producers. The mean duration of hospitalization were longer in patients infected with beta-lactamase producers (30.2±20.5 vs. 22.8±16.6 days P=0.05) and ESBL producing strains (29.13±20.39 vs. 19±9.84 P=0.05). ESBL production rate were determined 95.5% and 86.7% in Klebsiella pneumoniae by combined disk test (CDT) and double disk synergy test (DDST) method, respectively. These methods were positive for ESBL production in 78.6% and 64.3% of E. coli isolates, respectively.

Conclusion: in our study, the high rate of beta-lactamase and ESBL production were determined for common isolated organisms in neonatal sepsis. Infection with ESBL producing pathogens was associated with longer hospital stay. CDT method was detected more ESBL producing pathogens than DDST method in our study. It is recommended future studies to determine the risk factors predisposing newborn infants with these pathogens.