Tabaqchali S*, and Mitchelmore I.
Dept. of Medical Microbiology, St Bartholomew's Hospital, London EC1A 7BE, UK

Sinusitis is a common condition giving rise to increased morbidity and high economic costs. Treatment of sinusitis depends in part on the understanding of the microbial flora of the sinuses in these conditions. In this paper we report the findings in retrospective and prospective studies, specimens were obtained at surgery and cultured aerobically and anaerobically using specialised techniques.
327 samples obtained from 239 patients with sinusitis were cultured for aerobic and anaerobic bacteria and the results were analysed retrospectively. There were 683 bacterial isolates (2.1 isolate per specimen) of which 378 (55.3%) were aerobes or facultative aerobes and 305 (44.7%) were obligate anaerobes. Haemophilus influenzae and Streptococcus pneumoniae accounted for 72.9% of the aerobic flora, followed by S. aureus and Streptococcus milleri. Amongst the wide range of anaerobic bacteria, Peptostreptococcus micros, fusobacteria and pigmented Gram negative rods accounted for 68% of those grown in moderate to heavy growth.
This study was followed by a prospective study using gassed out bottles for transport of specimens. Forty five patients with sinusitis yielded 62 samples of which 48 were from chronic sinusitis and 9 from acute infections. The acute infections tended to have a single predominant isolate and only one of 9 grew an anaerobe. The chronic infections tended to be mixed with aerobes/anaerobes. Strep milleri were the comonest, usually associated with anaerobes, followed by H. influenzae, then Staph. aureus and Strep. pneumoniae. Peptostreptococcus micros was again the commonest anaerobic isolate followed by Prevotella buccae and F. nucleatum. Nine of the ten anaerobic infections grew one of the pigmented species of anaerobic Gram negative bacteria. B-lactamase producing bacteria were found in the sinuses of 20% patients.
These studies provide insight into the microbiology of sinusitis which has therapeutic implications and also show for the first time that Peptostreptococcus micros appears to play a prominent role in the infections of sinuses.