Tracking Clostridium Difficile Outbreaks with Multi-Locus Sequence Typing. R Sunday, Z Wang, Department of Molecular Diagnostics, Thomas Jefferson University Hospital, Philadelphia PA
Multi Locus Sequence Typing (MLST) is a powerful method for identifying unique bacterial strains that has recently be applied to tracking the changing epidemiology of Clostridium difficile (Griffiths et al). Common older methods for typing C. difficile infections such as PFGE, REA, and PCR Ribotyping, are too time consuming and cost inefficient for large scale studies. In order to help investigate increased rates of C. difficile infections at Thomas Jefferson University Hospital on the Bone Marrow Transplant Unit (P14A), MLST was set up to test stool specimens from C. difficile positive patients on the Bone Marrow Transplant Unit (P14A), as well as patients on the General Oncology Unit (N3WS) and on random other units. This study sought to evaluate the methodology from Griffiths et al to help determine the role of cross-transmission of C. difficile on P14A. Altogether, 66 samples, including 8 cultured isolates and 58 frozen whole stool specimens, were sequenced by MLST. A total of 22 stain types were identified across 3 of 4 major evolutionary lineages. The analysis of 27 samples from P14A/N3WS has shown a wide range of strains. Notably, typing of 3 isolates from a cluster of cases linked to an individual room on P14A revealed 3 different strains. These data suggest that most cases of C. difficile infections on the BMT unit are a result of prior colonization rather than cross-transmission. Future use of this methodology will require additional optimization of the DNA isolation protocol and the multiplex PCR reactions. Nonetheless this proved to be a powerful technique able to successfully sequence up to 12 samples in 2.5 days.