# Antimicrobial Resistance Trends Among Obligate Anaerobic Bacteria Isolated From Chronic Suppurative Otitis Media Patients in a Tertiary Care Teaching Hospital in Central India

## TL;DR

This study examines antimicrobial resistance in anaerobic bacteria from chronic ear infections in India, finding that clindamycin is more effective than ciprofloxacin.

## Contribution

The study provides new insights into anaerobic bacterial profiles and resistance patterns in CSOM patients in Central India.

## Key findings

- Obligate anaerobes were isolated in 12% of CSOM cases, with Gram-positive species predominating.
- Clindamycin showed the highest susceptibility (84.6%) among tested antibiotics.
- Ciprofloxacin had the lowest susceptibility (38.5%) in obligate anaerobe isolates.

## Abstract

Introduction: Chronic suppurative otitis media (CSOM) remains a major public health concern, especially in low- and middle-income countries, contributing significantly to preventable hearing loss. While aerobic bacteria are well-recognized pathogens in CSOM, anaerobic bacteria’s role is increasingly acknowledged due to improved sampling and culture techniques. Anaerobes may synergize with aerobes, worsening disease severity and complicating management. This study aimed to identify the anaerobic bacterial profile in CSOM patients and assess antimicrobial susceptibility patterns of these isolates.

Methods: A 12-month observational cross-sectional study was conducted at a tertiary care center in Central India, enrolling 100 patients aged >12 years with clinically suspected CSOM and chronic purulent ear discharge lasting ≥6 weeks. Pus samples were collected aseptically, inoculated in Robertson’s cooked meat medium, and processed for anaerobic culture following standard protocols. Isolates were identified using matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF; VITEK® MS PRIME, bioMérieux, France). Antimicrobial susceptibility testing (AST) of obligate anaerobes was performed by the E-test for metronidazole, clindamycin, ciprofloxacin, amoxicillin-clavulanic acid, and imipenem.

Results: Obligate anaerobes were isolated in 12% of cases, with Gram-positive anaerobes predominating. Finegoldia magna and Bacteroides fragilis were the most common species. The AST pattern varied between Gram-positive and Gram-negative obligate anaerobes. Clindamycin showed the highest susceptibility (84.6%), whereas ciprofloxacin demonstrated the lowest (38.5%).

Conclusion: Anaerobic culture and susceptibility testing are critical in managing CSOM, especially in refractory cases. Empirical use of ciprofloxacin should be cautious due to limited anaerobic coverage. Clindamycin and amoxicillin-clavulanic acid offer more reliable treatment options, potentially improving outcomes and mitigating antimicrobial resistance.