Anaerobic bacteria are associated with infections and significant mortality. "Anaerobic infections usually occur when an anatomical barrier becomes disrupted and constituents of the local flora enter a site that was previously sterile."2
Any body location may succumb to infection with anaerobic bacteria. Anaerobes may be present in the body as part of the normal bacterial microbiota (flora) or enter the body through perforation or trauma, surgery, or necrosis, reducing the ability of the skin or tissue barrier to be compromised. Host immunity may also affect the ability of anaerobic bacteria to proliferate and propagate.
In humans, anaerobes are part of the normal flora of the oral cavity, intestinal tract, and female genital tract. The urinary tract, organs, bone, blood, tissue, and body fluids (e.g., joint, pleural, thoracic) are normally sterile and free from bacteria. Age and overall health of the individual may play a part in the process. For example, breastfeeding infants have gut flora composed primarily of Bifidobacterium spp.; an adult's gut contains Escherichia coli (aerobe), Enterococcus spp. (aerobe), and Bacteroides spp. (anaerobe).
Body sites frequently associated with anaerobic infections include:
- Head and neck: peritonsillar or retropharyngeal abscesses; dental abscesses; gingivitis/periodontitis; sinusitis; otitis (ear); conjunctiva (eye)
- Perineal or perianal (pilonidal abscesses)
- Abdomen: intestinal abscesses; pelvic inflammatory disease
- Organs (e.g., brain, lung, liver)
- Bite infections (animal or human)
- Soft tissue (necrotizing infections)
- Bone or joint
- Blood (positive blood cultures are usually secondary to the primary infection site)
Important: Foul-smelling discharge usually accompanies an anaerobic infection. Although infrequent, these infections may carry a high mortality rate if not treated promptly.
2. Lee DG. Clinical significance of anaerobic infections. Korean J Intern Med. 2009;24(1):11-12. (Quote from page 11.) doi:10.3904/kjim.2009.24.1.11.Figure 2. Centers for Disease Control and Prevention. (1965). This cut section of human liver revealed the presence of numerous suppurative, or pus-containing lesions. [Image]. https://phil.cdc.gov/Details.aspx?pid=16157.Figure 3. Wikipedia Commons. (2011). Gangrene of the right foot in a person with diabetes. [Image]. https://en.m.wikipedia.org/wiki/File:Gangrene_Foot_01.jpg.
