The identification of gram-negative anaerobic bacilli isolated from clinical infections

Abstract

SUMMARY: Gram-negative anaerobic bacilli isolated from specimens submitted to the routine diagnostic bacteriology laboratory and regarded as significant pathogens were identified by conventional bacteriological tests; 399 strains isolated from 356 specimens submitted from 332 patients were studied and most were readily identified by the results of a combined set of morphological, biochemical, tolerance and antibiotic disk resistance tests.B. fragilishas particular pathogenic potential and was the commonest species isolated, accounting for < 50% of strains. The next commonest wasB. asaccharolyticuswith 55 strains, and 16 other species or groups were represented by smaller numbers. Many (68%) were from infections related to the gastro-intestinal tract, but there were significant numbers from infections of the male and female genito-urinary tracts, the head, neck and central nervous system and from a variety of soft tissue infections. Most infections were mixed, and a pure culture of aBacteroidessp. was obtained from only 26% of infections; two or more strains ofBacteroideswere recovered from 55 infections. The specific identification ofBacteroidesmay help the bacteriologist to judge the significance of laboratory findings, influence the patient's management and prognosis and help determine the source of infection.