Abstract

Lower respiratory tract infection (LRTI) caused by extended-spectrum β-lactamase (ESBL)-producing bacteria is a major health concern worldwide. Prompt diagnosis of ESBL-producing bacteria is critical for guiding appropriate antibiotic therapy and limiting the spread of ESBL pathogens. This study aimed to evaluate the antimicrobial susceptibility profile of Gram- negative isolates from sputum samples and to determine the proportion of multidrug-resistant (MDR) and ESBL Gram- negative isolates. The study was conducted in the microbiology laboratory of B & B Hospital Pvt. Ltd. from January to June 2023. The antimicrobial susceptibility pattern of the Gram-negative isolates was assessed using the modified Kirby-Bauer disc diffusion method on Mueller-Hinton agar (MHA), in accordance with Clinical and Laboratory Standards Institute (CLSI, 2020) guidelines, and MDR phenotypes were assigned accordingly. Ceftazidime and cefotaxime discs were used to screen isolates phenotypically for ESBL production, and combination discs with clavulanic acid were used to confirm ESBL production. A total of 148 sputum samples were collected and processed from clinically suspected LRTI patients. Of these, 39 (26.35%) samples showed bacterial growth. Gram-negative bacteria (34, 87.1%) were the most common isolates, most frequently recovered from male patients aged 41-60 years, and the majority of Gram-negative isolates (85.3%) were recovered from inpatients rather than outpatients. Gram-negative isolates were identified by colony morphology, Gram-stain reaction, and standard biochemical tests. Of the total isolates, Klebsiella pneumoniae (23, 58.97%) was the most frequently isolated organism. Among the 34 Gram-negative isolates, 20 (59%) were MDR. Of the 34 Gram-negative isolates, 13 (38.23%) were confirmed ESBL producers. Amikacin, gentamicin, and the carbapenems (imipenem and meropenem) were the most effective agents against the ESBL-producing isolates, whereas resistance to third-generation cephalosporins, fluoroquinolones, and cotrimoxazole was high; these agents should therefore be avoided for empirical LRTI therapy pending susceptibility results.