Isolation, characterization and classification of non-sporing gram-negative anaerobic bacilli (bacteroidaceae) from pathological specimens

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Bacteroides - Fusobacterium group of Gram-negative non-sporing anaerobic bacilli is known in hospital practice to be potential pathogens but the isolation and precise identification of these organisms are rarely attempt ted in most routine bacteriological laboratories. In my quest to investigate the major Bacteroides species frequently found in wound infections, six hundred and twenty (620) samples from the same number of patients with proven surgical infections were studied by conventional bacteriological methods and analysed. These specimens included pus, body fluids (including post-operative wounds), gingival abscesses and dental plaques taken from infected lesions associated with the mouth, the gastro-intestinal tract, the female genital tract and lower respiratory tract. Rapid anaercbic bacteria identification methods described by Rotimi, et al., 1980 were adopted. These in combination with Tolerance, Antibiotic disk resistance, physical and biochemical tests and a scheme by Duerden, et al., 1980 were employed in the quest to characterize and identify Gram-negative non-sporing anaerobic bacilli isolated from the various specimen sources. For purposes of isolation, samples were seeded on Columbia blood agar, selective Nalidixic Aoid-Vancomycin media and MacConkey agar and were incubated, both anaerobically and aerobically. It was noted that bacterial infections at the sites sampled were poly-microbial in nature. Fifty-five (55) bacterial isolates belonging to the species Bacteroides were identified, giving an isolation rate of 8.8% mostly as mixed cultures. From the mixed cultures could be identified aerobic and facultative anaerobic organisms by conventional methods suggested by Cowan, 1974. On the basis of growth characteristics, biochemical reactions and antibiotic sensitivity patterns, thirty (30) and, twenty five (25) isolates belonging to the Baoteroides fragilis group and the Baoteroidea melaninogenious - oralis group, respectively, were identified. The frequency of isolation of Baoteroides spp. from miscellaneous soft-tissue was 40%. It wan recognised that all the Beoteroides spp. identified tiers sensitive to metronidazole (Fingyl) but resistant to penicillin U. There were three hundred and twenty (320) aerobic and facultativo anaerobic organismt isolated and identified. Staiyloooocus aureus whioh represented 31, 2% of aerobic and feoultative anaerobic bacteria wan recorded. The importance of Baoteroides npp. involvement in post-operative wound infections was discussed. There is evidence that Bacteroides specie end aerobic organisms cooperate (synergistically) in the patho- genesis of Baoteroides spp. infection of wounds. Baoteroidees.-Fuso - bacterium bacilli commonly encountered in bacterial wound infections could be isolated and charaoterised using special media and 5e’t of biochemical tents. The importance of metronidazole (Flagyl) in anaerobic infections and in the control of sepsis complicating acute abdominal end pelvio conditions wan noted. In the study, it wan observed that Bacteroiden epp. played a role in the pãthogenenie of 8eptio surgical wounds. In conclusion it is suggested that further studies involving large numbers of patients in Teaching Hospitals should be recruited into the study, using improved techniques to demonstrate more fully’ the role and significance of anaerobic bacilli in acute abdomen and other surgical conditions seen in Ghana.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the award of the Degree of Master of Philosophy in Medical Microbiology, 1992