Abstract

Objective: To investigate the inducer AmpC (class C beta-lactamases) and extended spectrum β-lactamase in P. aeruginosa isolated from Chronic Suppurative Otitis Media (CSOM) patients.
Methodology: This cross-sectional study included 186 patients with CSOM and was conducted at the department of Ear, Nose and Thorat (ENT) at Jinnah Postgraduate Medical Centre (JPMC) in Karachi, Pakistan, from October 2022 to July 2023. Convenient sampling technique was applied. The microorganisms were identified using standard microbiological techniques. Subsequently, antibiotics susceptibility testing was carried out using the disk diffusion method, while the presence of AmpC and ESBL enzymes was determined through the D-test and double-disc synergy test (DDST), respectively.
Results: Out of 186 ear swab samples, 90% (169) showed significant bacterial growth. Among the growth positive, two samples showed fungal growth (1.18%). Gram-negative bacteria were found in 131 (77.51%) patients and Gram-positive bacteria in 36 (21.31%). Gram-negative bacteria, particularly P. aeruginosa, was found to be high 78 (59.54%). The resistance pattern of P. aeruginosa showed a higher resistance to ciprofloxacin and levofloxacin 35 (45%), gentamicin 33 (42%), ceftazidime 32 (41%) and cefepime 30 (38%) in comparison to imipenem 25 (32%), amikacin 24 (31%), meropenem 22 (28%), ticarcillin-clavulanate 34 (44%), and piperacillin-tazobactam 20 (26%). AmpC and ESBL were detected in 43 (55%) and 14 (18%) of P. aeruginosa isolates, respectively.
Conclusion: P. aeruginosa predominated in CSOM cases, showing a high incidence of AmpC production, highlighting treatment challenges.

Key words: Antibiotic resistance, AmpC beta-lactamase, chronic suppurative otitis, Pseudomonas aeruginosa.