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

Abstract

SUMMARYGram-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. fragilis has particular pathogenic potential and was the commonest species isolated, accounting for > 50 % of strains. The next commonest was B. asaccharolyticus with 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 a Bacteroides sp. was obtained from only 26 % of infections; two or more strains of Bacteroides were recovered from 55 infections. The specific identification of Bacteroides may help the bacteriologist to judge the significance of laboratory findings, influence the patient's management and prognosis and help determine the source of infection.

The Bactericidal Action of Human Serum on Bacteroides Species

“…B. fragilis, the type-species of the group, is a less common member of the normal anaerobic flora of the faeces but is the commonest species isolated from clinical infections after abdominal or pelvic surgery (Holland et al, 1977;Duerden, 1980b).…”

“…and anaerobic cocci have been increasingly implicated in a number of clinical infections, some of which were life-threatening (Sinkovics and Smith, 1970;Felner and Dowell, 197 1;Bartlett and Finegold, 1972;Gorbach and Bartlett, 1974;Rotimi and Abudu, in press). B. fragilis, the type species of the B. fragilis group which includes B. thetaiotaomicron, B. vulgatus, B. fragilis, B. ovatus and B. distasonis, is the species most commonly isolated from human infections (Holland, Hill and Altemeier, 1977;Polk and Kasper, 1977;Duerden, 1980b). These anaerobes have often been regarded as opportunistic pathogens which express their pathogenic potential when the integrity of the host defence is breached.…”

A scheme for the identification of clinical isolates of gram-negative anaerobic bacilli by conventional bacteriological tests

“…This suggests that B. f r a g i h has either an effective mechanism to evade the host defences or special aggressive potential that may be related to cell-surface properties (Kasper, 1976) or the formation of diffusible products (Gesner and Jenkin, 1961;Muller and Werner, 1970). The identification of B. asaccharolyticus and B. melaninogenicus strains may also have particular significance (Duerden, 1979(Duerden, , 1980. The identification of Bacteroides isolates may, therefore, help in assessing the significance of laboratory findings and in determining the source of an infection when this is not immediately apparent.…”

Characteristics of a gram-negative anaerobe isolated from men with non-gonococcal urethritis

“…Suspensions of organisms prepared from pure cultures were seeded on BHIA-FFN and tested with Whatman A/A filter-paper disks (Baird and Tatlock) impregnated with sodium taurocholate 2.5%, sodium deoxycholate 0.5%, and a mixutre of both (Duerden et a/., 1980). Zones of inhibition were recorded after anaerobic incubation at 37'C for 3 days.…”

“…Anaerobes are now thought to be implicated in a wide variety of urogenital-tract infections in men (Duerden, 1980). They have also been associated, in women, with the so-called "urethral syndrome", also known as dysuria-frequency syndrome (Maskell, Pead and Allen, 1979;Gargan, Brumfitt and Hamilton-Miller, 1980).…”