Abstract
Objective: To assess the frequency of extended spectrum β- lactamases (ESBLs) producers in clinical isolates of Gram-Negative Bacilli (GNB) and analyze their distribution among the three common GNB pathogens.
Methodology: This prospective, cross-sectional study included GNB pathogens from the pus and urine samples collected from the patients suspected of urinary tract infections or wound infections, respectively. The isolated bacteria were identified based on their cultural, microscopic, and biochemical characteristics. API-E20 kit was used, where necessary. Antibiotic susceptibility profiling of the GNB isolates was determined according to CLSI guidelines. The production of ESBLs by GNB isolates were determined using double disc and combined disc synergy tests.
Results: Out of 256 growth positive clinical samples, 171 (66.79%) were identified as GNB, which included Escherichia coli (57.06%; n=101), Klebsiella pneumoniae (19.20%; n=36) and Pseudomonas aeruginosa (19.20%; n=34). Antibiotic susceptibility testing showed that the highest β- lactam resistance occurred in K. pneumoniae with 83.33% (n=30) resistant isolates followed by E. coli with 78.22% (n=79) isolates, while 29.41% (n=10) of P. aeruginosa isolates were resistant to the β- lactam antibiotics tested. The ESBLs production tests for the β- lactam resistant GNB isolates showed high prevalence of ESBLs producers among them.
Conclusion: Higher frequency of ESBLs producers among GNB pathogens were observed. It has caused the emergence of carbapenem resistance in these pathogens, resulting in limited treatment options for the cure of GNB associated infections.

Key words: Gram-negative bacilli, extended spectrum β-lactamases, β- lactams, antibiotics resistance.