Abstract

Background: Antimicrobial resistance is a global threat in the medical society. Extended- Spectrum β-lactamase (ESBL) producing bacteria are increasing worldwide, including Nepal and causing more severe infections because of their continuous mutation and multidrug resistance (MDR) nature.

Objective: The objective of this study was to assess Gram-negative bacterial etiology of lower respiratory tract infections (LRTIs) and determine their antibiotic susceptibility pattern with a special focus on MDR, including ESBL production.

Methods: A total of 109 sputum specimens were analyzed. The bacterial isolates were identified by standard microbiological procedures, including Analytical Profile Index (API) 20E test panels for Enterobacteriaceae and subjected to antimicrobial susceptibility testing. Screening of ESBL producers among Gram-negative isolates was done by using third-generation cephalosporins (ceftazidime and cefotaxime) and confirmed by the combined disk method as recommended by CLSI (2019).

Results: Out of 109 sputum specimens, Gram-negative bacterial etiology was determined in 31(28.4%) cases. The age-wise distribution of LRTIs patients was found to be statistically significant with bacterial incidence (p<0.05). Altogether, 15(46.9%) isolates were multidrug-resistant. ESBL producers were observed only among Klebsiella spp. and Escherichia coli isolates. On the ESBL screening test of 9 isolates (3 of E. coli and 6 of Klebsiella spp.) 5(55.6%) gave a positive result, and only 3(33.3%) of them were further confirmed as ESBL producers. The majority of ESBL producers (66.7%) were Klebsiella spp.

Conclusion: The present study revealed that multidrug resistance is prevalent among Gram-negative bacterial pathogens isolated from the patients with lower respiratory tract infections, requiring routine laboratory testing for MDR and ESBL production in clinical isolates for better prophylaxis and reducing the risk of ESBL transmission.

Keywords: Lower respiratory tract infection, Gram-negative bacteria, Antibiotic susceptibility testing, MDR, ESBL, Combined Disk (CD) assay.

Graphical Abstract