Molecular characterization of Extended Spectrum Beta lactamases producing bacteria causing Chronic Suppurative Otitis Media in South India

Chronic suppurative otitis media (CSOM) is one of the most common middle ear infections leading to extra and intracranial complications if not diagnosed promptly. Early identification and detection of the etiological agents and antibiotic susceptibility patterns assist in preventing complications.

Two hundred twelve ear swabs were collected using sterile cotton swabs. Direct gram staining was done and then inoculated into blood, MacConkey, and Nutrient agar. Bacterial isolates were identified using conventional methods. According to CLSI guidelines, Antibiotic susceptibility testing was performed by Kirby-Bauer disc diffusion method. Minimum inhibitory concentration (MIC) was performed by the agar dilution method. Extended-spectrum beta-lactamases producing bacteria were detected by the phenotypic confirmatory test and then corroborated by uniplex PCR.

Out of 212 samples, 157 samples (74.06%) were culture-positive for bacteria. The isolated bacteria included Pseudomonas aeruginosa (46.24%), Staphylococcus aureus (26.59%), Klebsiella pneumoniae (14.45%), coagulase-negative Staphylococcus aureus (5.20%), Proteus mirabilis (4.05%), Enterococcus faecalis (2.89%), and Escherichia coli (0.58%). The P. aeruginosa isolates showed 96.25% and 95% susceptibility to amikacin and ofloxacin, respectively. All Gram-negative bacilli isolates were 100% sensitivite to imipenem. Ten (30.30%) isolates were ESBL producers with the CTX-M-14 gene detected in most of them.

Our study found that P. aeruginosa was the most common isolated pathogen bacteria. Knowledge of CSOM causing bacteria and their susceptibility to antibiotics would help choose an appropriate treatment, thereby preventing antibiotic resistance and complications in these cases.