LEPTOTRICHIA BUCCALIS BACTEREMIA IN PATIENTS TREATED IN A SINGLE BONE-MARROW TRANSPLANT UNIT

We describe four cases of bacteremia due to Leptotrichia buccalis (an organism that is part of the normal human oral flora) that occurred in a bone marrow transplant unit over a 3-month period. All of the patie nts were neutropenic, all had mucositis or esophagitis, and all were r eceiving antimicrobial prophylaxis with ciprofloxacin and vancomycin ( drugs to which Leptotrichia is resistant). One patient died of adult r espiratory distress syndrome; the others had minimal symptoms. Pulsed field gel electrophoresis of bacterial DNA digested with Sma I demonst rated a unique banding pattern for each isolate, indicating that the i solates belonged to distinct strains. Quantitative gas-liquid chromato graphy of whole-cell free fatty acids confirmed the uniqueness of the strains, obviating the need to search for a common source of infection . We postulate that this outbreak resulted from antibiotic selection p ressure on the oral flora in patients who had been compromised by seve re neutropenia and mucosal disruption.