Objective To evaluate the organisms recovered from infected sinuses and associated intracranial abscesses (IAs).
Design Retrospective review of findings from aspirate of pus from 10 infected sinuses and their corresponding IAs.
Setting Academic medical center.
Patients Ten patients diagnosed as having sinusitis (age range, 7-58 years).
Main Outcome Measure Aerobic and anaerobic bacteria findings from infected sinuses and IAs.
Results Polymicrobial flora was found in 9 sinuses and 8 IAs. Anaerobes were isolated from all sinuses and 9 IAs. A total of 26 isolates (2.6 isolates per specimen) were recovered from the sinuses: 19 anaerobic, 6 aerobic or facultative, and 1 microaerophilic; 17 isolates were found in the IAs (1.7 isolates per site): 13 anaerobic, 2 aerobic or facultative, and 2 microaerophilic. The predominant anaerobes were Fusobacterium species (in 5 corresponding sinuses and abscesses, 1 in a sinus only, and 1 in an IA only), Prevotella species (in 3 corresponding sinuses and abscesses), Peptostreptococcus species (in 2 corresponding sinuses and abscesses, and 4 in a sinus only), Staphylococcus aureus, Haemophilus influenzae type b, microaerophilic streptococci, and Bacteroides ureolyticus (in 1 corresponding sinus and abscess each). Streptococcus pneumoniae was recovered 2 times, only from a sinus. 
-Hemolytic streptococci and 
-hemolytic streptococci group F were each isolated once from the sinus. Concordance in the microbiological findings between the sinus and the IA was found in all instances. However, certain organisms were present at only one or the other site.
Conclusion These data illustrate the concordance in the recovery of organisms from infected sinuses and their associated IA and confirm the importance of anaerobic bacteria in sinusitis and IA.
