Very little up-to-date information is available on the microbiology of complicated acute bacterial rhinosinusitis. Reliable microbiology testing is necessary to inform current empirical antimicrobial treatments. This study was conducted in response to recent US guidelines on antimicrobial treatments for acute bacterial rhinosinusitis. It aimed to describe the pathological micro-organisms involved in complicated acute bacterial rhinosinusitis in the UK and their antimicrobial susceptibility.

This study collected retrospective data on cases of complicated acute bacterial rhinosinusitis with sinogenic orbital and/or intracranial infections from 2007 to 2012. Bacteria identified in paranasal sinus pus were compared with those identified in orbital and/or intracranial infections.

Streptococcus anginosus group bacteria were isolated from 61.3 per cent of paranasal sinus pus samples, 83.3 per cent of orbital infections and 77.8 per cent of intracranial infections. All S anginosus isolates were sensitive to penicillin; no penicillin-resistant organisms were isolated.

S anginosus was the predominant organism isolated from complicated acute bacterial rhinosinusitis samples at our UK centre. S anginosus is sensitive to penicillin, suggesting that penicillin can be used as an appropriate first-line empirical antibiotic for uncomplicated acute bacterial rhinosinusitis.