We describe two recent cases of bacteraemia caused by Leptotrichia trevisanii in febrile neutropenic patients with haematological malignancies. Identification of the organism is important to direct appropriate antibiotic therapy in this group of severely immunocompromised patients. Some clinical and diagnostic information will be presented.

Leptotrichia species are non-motile, aerotolerant, anaerobic Gram negative rods belonging to the family Fusobacteriaceae that are found as part of the normal flora of the oral, intestinal and female genital tract in humans.

Identification of this organism was problematic using conventional methods based on biochemical reactions. Matrix-asssisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS )  identified this organism. Molecular methods with 16S r DNA gene sequencing confirmed the isolate as Leptotrichia trevisanii.

These cases highlight the opportunistic nature and pathogenic potential of Leptotrichia species. They serve as a reminder to scientists and clinicians in the  diagnostic microbiology laboratory  to consider this organism when conventional tests fail to identify anaerobic Gram negative rods from blood cultures. Furthermore, the use of new laboratory technologies such as MALTI-TOF  have the potential to identify difficult organisms accurately and rapidly.