Aerobic and anaerobic microbiology of acute suppurative parotitis. Aspirates of pus from acute suppurative parotitis were studied for aerobic and anaerobic bacteria. Bacterial growth was present in 23 specimens. A total of 36 bacterial isolates (20 anaerobic and 16 aerobic and facultative) were recovered, accounting for 1.6 isolates per specimen (0.9 anaerobic and 0.7 aerobic and facultative). Anaerobic bacteria only were present in 10 (43%) patients, aerobic and facultatives in 10 (43%), and mixed aerobic and anaerobic flora in 3 (13%). Single bacterial isolates were recovered in 9 infections, 6 of which were Staphylococcus aureus and 3 were anaerobic bacteria. The predominant bacterial isolates were S. aureus (8 isolates), Bacteroides sp. (6 isolates, including 4 Bacteroides melaninogenicus group), and Peptostreptococcus sp. (5). beta-Lactamase-producing organisms were recovered from 11 (73%) of the 15 specimens tested. This study highlights the polymicrobial nature and importance of anaerobic bacteria in acute suppurative parotitis. 