Bacteriological spectrum, antimicrobial susceptibility, and year-to-year variation among referred culture-positive presumed chronic suppurative otitis media specimens in a Syrian reference laboratory (2022-2025).

backgroundChronic suppurative otitis media (CSOM) remains an important cause of chronic otorrhea and preventable hearing impairment, particularly in resource-limited settings. Because bacterial profiles and antimicrobial susceptibility patterns vary across settings, local laboratory surveillance may support culture-guided management, especially in persistent or previously treated cases.

methodsWe conducted a retrospective laboratory-based study at a private reference laboratory in Damascus, Syria. The analyzed cohort primarily represents referred laboratory specimens rather than a population-based CSOM sample. Culture-positive aerobic bacterial isolates recovered from purulent ear-discharge specimens classified as presumed CSOM were included between January 1, 2022, and December 31, 2025. Presumed CSOM was operationally defined as culture-positive purulent otorrhea associated with documented tympanic membrane perforation in the referral/laboratory context. Isolates were deduplicated across the study period by retaining only the first isolate of a given bacterial species per patient. Antimicrobial susceptibility testing was performed as part of routine laboratory workflow and interpreted according to CLSI M100, 30th edition, 2020. Susceptibility was reported as percent susceptible with corresponding denominators.

resultsA total of 638 culture-positive bacterial isolates were analyzed. The mean age was 34.75 ± 24.42 years, and 322 patients were male (50.5%). Gram-positive organisms slightly predominated over Gram-negative organisms (56.0% vs 44.0%). Methicillin-susceptible Staphylococcus aureus was the most frequent isolate (311/638, 48.7%), followed by Pseudomonas aeruginosa (233/638, 36.5%). MRSA accounted for 26 isolates (4.1%). MSSA showed high in vitro susceptibility to vancomycin, linezolid, and teicoplanin, but low susceptibility to ciprofloxacin, azithromycin, clindamycin, and trimethoprim-sulfamethoxazole. P. aeruginosa showed highest in vitro susceptibility to colistin, meropenem, amikacin, imipenem, and piperacillin-tazobactam, while ciprofloxacin susceptibility was low. Exploratory annual analyses showed year-to-year variation in susceptibility for several agents among MSSA and P. aeruginosa.

conclusionsThis Damascus reference-laboratory study provides contemporary bacteriological and susceptibility data for referred culture-positive purulent otorrhea specimens classified as presumed CSOM. The findings should be interpreted as local laboratory surveillance data rather than nationally representative CSOM epidemiology or direct treatment guidance for uncomplicated community cases. The low fluoroquinolone susceptibility observed in this referred cohort supports culture and susceptibility testing in recurrent, persistent, or previously treated otorrhea, while preserved activity of reserve systemic agents should be interpreted within antimicrobial stewardship principles.