Newly emerging metronidazole-resistant Clostridioides difficile PCR ribotype 955 identified in Poland, 2021 to 2023 but not in Czechia, 2012 to 2023 and Slovakia, 2015 to 2023

Abstract

Background: On 29 January 2024, the European Centre for Disease Prevention and Control distributed an alert about a metronidazole-resistant Clostridioides difficile outbreak of PCR ribotype (RT) 955 in England. Aim: We aimed to investigate the presence of RT955 in Czech, Slovak and Polish C. difficile isolates and evaluate different culture media for detecting its metronidazole resistance.

Methods: Isolates with binary toxin genes identified as 'unknown' by the WEBRIBO PCR ribotyping database up to 2023 were re-analysed after adding the RT955 profile to the database. The RT955 isolates were characterised by whole genome sequencing and tested for susceptibility to 15 antimicrobials.

Results: We did not find RT955 in Czech (n = 6,661, 2012-2023) and Slovak (n = 776, 2015-2023) isolates, but identified 13 RT955 cases (n = 303, 2021-2023) in three hospitals in Poland. By whole genome multilocus sequence typing, 10 isolates clustered into one clonal complex including a sequence of United Kingdom strain ERR12670107, and shared similar antimicrobial resistance genes/mutations. All 13 isolates were resistant to ciprofloxacin/ moxifloxacin, erythromycin/clindamycin and ceftazidime. All isolates had a mutation in the nimB gene promoter and in NimB (Tyr130Ser and Leu155Ile). The metronidazole resistance was detected in all isolates using brain-heart-infusion agar supplemented with haemin and Chocolate agar. Results were discrepant with the European Committee on Antimicrobial Susceptibility Testing-recommended Fastidious anaerobe agar and Brucella blood agar. Conclusion: The identification of clonally related haem-dependent metronidazole-resistant C. difficile RT955 in multiple hospitals indicates a need for prospective surveillance to estimate its prevalence in Europe.