Bacteroides Bacillemia

Abstract

Bacteroidesspecies are anaerobic, aero-intolerant, nonsporeforming, nonmotile, gram-negative bacilli that colonize the oropharynx, female genital tract, and large bowel, comprising 95% of the colonic bacterial population and 20% of the dry weight of stool. Bacteriologic identification ofBacteroidesorganisms is frequently difficult because they are fastidious, sometimes slow-growing, and often resembleEscherichia coliand other gram-negative bacilli morphologically. Specimens infected byBacteroidesorganisms may contain many gram-negative rods on gram stain but show no growth on culture if not inoculated promptly into anaerobic media. Infections are often mixed and sometimes fail to yieldBacteroidesorganisms because of overgrowth by less fastidious bacteria. Commonly, the clinician first recognizesBacteroidesinfection in his patient when the laboratory reports blood cultures positive. Accumulating experience suggests that the apparent incidence of bacillemia due toBacteroidesorganisms is rising. In 1971 in the Mayo Clinic,Bacteroideswas the second most common gramnegative bacillus isolated from