No 24 - 2020

Increase in Clostridioides (previously Clostridium) difficile ST37/PCR ribotype 017

Clostridioides difficile (C. difficile) is a bacterium that causes diarrhoea and inflammation of the bowel. This condition mainly affects weakened elderly persons and chronically ill patients who are receiving antibiotics treatment and who constitute a considerable challenge in relation to hospital infection control.

In the course of 2018 and 2019, Denmark has seen a rise in the number of registered cases of a novel type of C. difficile (ST37, PCR ribotype 017), which demands attention. In particular, two circumstances apply:

• This type has a 30-day mortality of 32% (calculated based on 2018-19 infections), which is considerably higher than that of other types.

• It is multi-resistant as it shows genotypic resistance to fluoroquinolone, aminoglycoside, tetracycline, macrolide and rifampicin.

A very limited number of cases were detected before 2018, but 2018 and 2019 recorded 16 and 12 cases, respectively. The type is also special in that it is positive to Toxin B (TcdB) and negative to both Toxin A (TcdA) and the binary toxin (CdtAB), meaning that it is mainly recorded in the sentinel surveillance, which covers approx. 16% of the samples made in Denmark. Therefore, the real number is probably substantially higher. The mentioned Danish cases are spread across the country with a preponderance in the Greater Copenhagen Area, and only very few cases were from the same hospital department or have been linked epidemiologically. The type has caused several serious outbreaks abroad and is considered endemic in parts of Asia (see, e.g., PMID:31138041) and is therefore considered a potentially travel-associated agent.

The Danish sentinel surveillance scheme for C. difficile is a collaborative effort involving all ten departments of clinical microbiology (DCM) and Section for Foodborne Infections at the SSI. The DCMs submit all toxin-positive samples/isolates (at least TcdA or TcdB) to the SSI for typing during one month in spring and one month in autumn. This ensures a more real and unselected image of the type distribution in the Danish reservoir, where increases and decreases may be followed more easily. It also serves to record unusual types as the one mentioned above, which due to its toxin profile is not registered through conventional monitoring, which has been focused on binary toxin-positive types like, e.g., PCR of ribotype 027.

(S. Persson, Section for Foodborne Infections, Department of Bacteria, Parasites and Fungi)