Isolation of presumptive Streptobacillus moniliformis from abscesses associated with the female genital tract.

We report three cases in which Streptobacillus moniliformis was isolated from abscesses. Abscess material in each case contained small, pleomorphic, gram-negative to gram-variable bacilli. Anaerobic blood agar cultures yielded pinpoint colonies adjacent to small gray-white colonies. The pinpoint colonies did not gram stain, and the gray-white colonies varied from gram-variable coccobacilli to long, curly, gram-variable rods. The pinpoint colonies microscopically resembled L-forms on Dienes-stained agar preparation. Subculture to serum-supplemented thioglycolate broth demonstrated "puff ball" colonies. Fatty acid profiles obtained with use of gas chromatography coupled with mass spectrometry showed major peaks for C16:0, C18:2, C18:1, and C18:0 fatty acids, a profile characteristic of S. moniliformis. Results of biochemical testing of each isolate were equivocal. S. moniliformis, bacterial L-forms, and common isolates from genital tract abscesses are discussed.