HMW-profiling using MALDI-TOF MS: A screening method for outbreaks of Clostridioides difficile.

Clostridioides difficile (CD), previously known as Clostridium difficile, is an anaerobic Gram-positive rod-shaped bacterium that causes mild to severe diarrhea mainly in hospitalized patients. The bacteria are easily spread between patients and can persist in hospital wards due to its ability to form spores. An outbreak of CD causes great sufferings for patients and is in many aspects very expensive for the health care organization. Continuously monitoring circulating CD isolates in the hospital as well as being able to detect possible spread between patients at an early phase would be of great benefit. Recently a new method was published by Rizzardi et al. (2015) where CD can be typed to a High Molecular Weight (HMW)-profile using Matrix-Assisted Laser Desorption Ionization -Time of Flight Mass Spectrometry (MALDI-TOF MS). We analyzed 1000 isolates of toxin-positive CD with this method and compared the frequency of profiles within different hospitals as well as between two counties in the south-east part of Sweden. During the study period we could detect three outbreaks of CD in three different hospitals. One was an outbreak of CD with ribotype 027, resulting in severe consequences. The method was easily implemented at the clinical microbiology routine diagnostic laboratory and in collaboration with the hospitals Infection Control Units it is a very useful and cost-effective tool to detect outbreaks of CD at an early stage.