Clinical audit of the microbiology of otorrhoea referred to a tertiary hospital in Singapore

Cheong C, Tan ML, Ngo RY
Correspondence: Dr Raymond Ngo, raymond_ngo@nuhs.edu.sg

ABSTRACT
Introduction Otorrhoea is a common complaint in Ear, Nose and Throat clinics. This study aimed to establish the pathogens involved in cases of otorrhoea in Singapore, their sensitivity patterns and the effectiveness of empirical  management. 
Methods A retrospective chart review was conducted on 91 patients with otorrhoea who had undergone swab cultures between July 2010 and February 2011. 
Results Of the 91 cases, 53% were diagnosed empirically as bacterial otitis externa and 25% as otomycosis. Aerobic bacteria accounted for 35.8% of the microorganisms cultured, while 34.7% were fungi and 29.5% were anaerobic bacteria. Pseudomonas (P.) aeruginosa and Staphylococcus (S.) aureus made up 31.6% and 21.0% of the microorganisms, respectively. 20% of S. aureus grown was methicillin-resistant. Aspergillus was the most common fungus and 19% of cultures were polymicrobial. 38% of patients had their treatment changed on the basis of culture results, as no improvement was observed on follow-up. P. aeruginosa was sensitive to ciprofloxacin and gentamicin in 81.8% and 76.0% of patients, respectively, while S. aureus was sensitive to cloxacillin in 93.8% and clindamycin in 87.5% of patients. 
Conclusion The common microorganisms involved in otorrhoea in Singapore are P. aeruginosa, Aspergillus and S. aureus. Resistant strains of Pseudomonas spp. are now present. Methicillin-resistant S. aureus is increasingly prevalent and highly sensitive to vancomycin. Aminoglycoside and fluoroquinolone-containing eardrops are suitable first-line topical antimicrobials. Cloxacillin may be started should a concomitant oral antimicrobial be warranted empirically or for S. aureus infections. Otomycosis should be considered in patients who show no improvement with antibiotics.

Keywords: chronic suppurative otitis media, ear discharge, otitis externa, otomycosis, otorrhoea
Singapore Med J 2012; 53(4): 244–248