Microbiology of subperiosteal orbital abscess and associated maxillary sinusitis.

Aspirate of pus from eight subperiosteal orbital abscesses (SPOAs) and their corresponding infected sinuses were studied for aerobic and anaerobic bacteria. Polymicrobial flora was found in all instances, and the number of isolates varied from two to five. Anaerobes were recovered from all specimens. The predominant isolates were Peptostreptococcus spp, Prevotella spp, Fusobacterium spp, Staphylococcus aureus, and microaerophilic streptococci. Concordance in the microbiological findings between SPOA and the infected sinus was found in all instances. However, certain organisms were only present at one site and not the other. Fourteen beta-lactamase-producing organisms were present in nine specimens. These data confirm the importance of anaerobic bacteria in sinusitis and demonstrate their predominance in the associated SPOA.