BACTEROIDES

(under the microscope)
The Bacteroides genus of anaerobic bacteria comprise the majority of microorganisms that inhabit the digestive tract. 50% of most fecal matter is actually Bacteroides fragilis cells! Bacteroides organisms are the anaerobic counterpart of E. coli except they are somewhat smaller. They grow well on blood agar, and under the microscope, they may contain large vacuoles that are similar in appearance to spores. Members of Bacteroides species are not spore-forming, but they do produce a very large capsule. Their pathogenicity is limited, however, because they possess no endotoxin in their cell membrane. Infection only occurs after severe trauma to the abdominal region. Infection could lead to abscess formation and possibly fever. Antibiotic treatment usually consists of metronidazole or clindamycin.

LABORATORY INDICATIONS (B. fragilis):
• Indole -
• Catalase +
• Esculin hydrolysis +
• Glucose fermentation
• Lactose +