Bacteriology of abscesses of the central nervous system: a multicentre prospective study

Pus from 46 patients with abscesses of the central nervous system (CNS) was examined for bacteria; bacteria were found in all patients. Streptococci were isolated from 36 patients and most isolates were Streptococcus milleri, Lancefield Group F, Ottens and Winkler type O III. Staphylococci were isolated from nine patients, organisms of the bacteroides group from 11, Proteus spp from seven, Klebsiella aerogenes from one, and Haemophilus aphrophilus from one. Pure cultures predominated over mixed cultures. Streptococci were isolated from abscesses of all types, and at all sites, but members of the Enterobacteriaceae and of the bacteroides group were isolated, in mixed cultures, principally from abscesses of the temporal lobe secondary to infection of the middle ear. Staphylococci predominated in abscesses that followed accidental or surgical trauma. Compared with fully sensitive control organisms, microbes infecting half the patients were resistant to penicillin. The prognosis of abscess of the CNS is grave, and the microbiological findings have important consequences for treatment. Prompt inoculation of specimens to culture plates and prompt incubation are mandatory if bacteria are to be cultured. Inhibitors of antimicrobial agents should be added to culture media if antibiotics have been administered. Provided that the site of the abscess and the antecedent history are ascertainable, the neurosurgeon should be able to start appropriate treatment while awaiting the results of culture.