Answer: Leptotrichia buccalis bacteremia. On the second day of incubation, two FN anaerobic-blood-culture bottles yielded an anaerobic Gram-negative bacillus that could not be identified by the routine identification methods used in our laboratory. The isolate was sent to Mayo Medical Laboratories for additional testing. Partial 16S rRNA sequencing produced a result that was a 99.66% match to Leptotrichia buccalis from the MicroSeq database. Antimicrobial susceptibility testing performed by Mayo Medical Laboratories indicated that the isolate was susceptible to clindamycin, metronidazole, and penicillin. Before the organism identification was finalized, the patient was discharged home and completed a 6-day course of meropenem.
Leptotrichia buccalis is closely related to Fusobacterium spp. It is a large, fusiform, nonmotile, nonsporulating rod that is anaerobic or aerotolerant and saccharolytic. It is normal flora in the intestinal tract and the female genitourinary tract. L. buccalis has been identified as a causative agent of gingivitis and periodontitis (1), particularly affecting patients with hematologic malignancies (2–5), with a particularly high risk for bone marrow transplantation patients (2, 3). In a 4-year retrospective case-control study of patients undergoing bone marrow transplants, Leptotrichia buccalis was the second most common anaerobic Gram-negative organism isolated from blood cultures. Mucositis, such as was experienced by our patient, is a potential risk factor for septicemia (3). L. buccalis is usually resistant to vancomycin, macrolides, quinolones, and aminoglycosides and susceptible to tetracyclines, metronidazole, clindamycin, penicillins, and cephalosporins (5).
(See page 389 in this issue [doi: 10.1128/JCM.01154-12] for photo quiz case presentation)
ACKNOWLEDGMENT
We thank William Tyler for taking the photograph used in this photo quiz.
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