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Anaerobic bacteria are the greatest component of the human body's normal bacterial flora colonizing the skin, oral cavity, and genitourinary and lower gastrointestinal tracts. Their presence is important in promoting vitamin and other nutrient absorption and in preventing infection with pathogenic bacteria.
Anaerobes generally are of low pathogenicity, but may possess virulence factors such as endotoxin or polysaccharide capsules or produce extracellular toxins. Disease occurs when a large inoculum develops in an area lacking oxygen or with a poor blood supply.
Typical anaerobic infections include peritonitis, abdominal or pelvic abscesses, endometritis, pelvic inflammatory disease, aspiration pneumonia, empyema, lung abscesses, sinusitis, brain abscesses, gas gangrene, and other soft tissue infections. Many Bacteroides produce beta-lactamase and are resistant to penicillins and cephalosporins. Imipenem, metronidazole, and clindamycin are effective agents, although resistance to clindamycin is increasing.
Identification of anaerobic bacteria involved in human infections
Isolation of anaerobes in significant numbers from well-collected specimens from blood, other normally sterile body fluids, or closed collections of purulent fluid indicates infection with the identified organism.
No significant cautionary statements
Identification of organism
1. Jousimies-Somer HR, Summanen P, Citron DM, et al: Wadsworth Anaerobic Bacteriology Manual. Sixth edition. Belmont, CA, Star Publishing Co. 2002
2. Anaerobic Bacteria. Chapters 50-54. In Manual of Clinical Microbiology. 11th edition. Edited by JH Jorgensen, MA Pfaller. Washington, DC, ASM Press, 2015
3. Hall GS: Section 4. Anaerobic bacteriology. In Clinical Microbiology Procedures Handbook. Vol 1. Third edition. Edited by LS Garcia. Washington, DC, ASM Press, 2010