Bacteriology of brain abscess--observations on 50 cases.

The bacteriology of brain abscess is complex--both aerobic and anaerobic organisms are involved, and their incidence varies from centre to centre. In this study of 50 consecutive cases of brain abscess, the value of both modern imaging techniques and the time-honoured Gram's stain was demonstrated. The Gram's stain showed organisms in 41 cases (82%) and culture was positive in 44 cases (88%). Thirty cultures yielded pure aerobic growth: Staphylococcus aureus, beta-haemolytic streptococci and Proteus spp. were predominant. Five cases gave mixed aerobic cultures, and in seven cases anaerobes were isolated. Of these, three showed a mixed aerobic and anaerobic flora. Mycobacterium tuberculosis was cultured from one of the samples, which had shown acid-fast bacilli on direct smear. M. fortuitum was cultured from one sample, although no organisms were seen in the gram-stained preparation.