Identifying PCR-ribotype 017-lineage isolates of Clostridioides difficile using MALDI-TOF MS

The PCR-ribotype (RT) 017-lineage of Clostridioides difficile, which is toxin A-negative, toxin B-positive, and binary toxin-negative (A^-B⁺CDT^-), has been endemic/epidemics particularly in Asia. In Japan, since the early 2000s, among RT017-lineage C. difficile, RT017 has been replaced by RT369, which is multidrug-resistant and has been responsible for outbreaks. We report a rapid method for identifying A^-B⁺C. difficile using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS).

We analyzed 79 toxigenic isolates, including 37 A^-B⁺CDT^- isolates and 42 isolates with other toxin profiles (A⁺B⁺CDT^-, A⁺B⁺CDT⁺, and A^-B⁺CDT⁺).

Peaks at m/z 3289 and 3245 were detected in all 37 A^-B⁺CDT^-C. difficile, including the 22 RT369 isolates, but not in 42 non-A^-B⁺CDT^- isolates. The method showed 100 % sensitivity and specificity in detecting A^-B⁺CDT^-.

The Identification of RT017-lineage C. difficile including RT369, which is an A^-B⁺CDT^- strain causing outbreaks in Japan, by MALDI-TOF MS can be used as an additional tool to be implemented in the routine identification processes. The difference of media often used for C. difficile culture in clinical laboratories, did not affect the MALDI-TOF MS results.