Dominance of Toxigenic Clostridioides difficile Strains and the Appearance of the Emerging PCR Ribotype 955 in Hospitals in Silesia, Poland

Klaudia Szarek¹Natalia Frankowska^2,3Monika Kabała^1*Wiep Klaas Smits⁴Dorota Wultańska⁵Piotr Lalowski⁵Hanna Pituch⁵Adam Iwanicki²Krzysztof Hinc²Céline Harmanus⁴Ingrid M J G Sanders⁶Robert Dariusz Wojtyczka⁷Tomasz J. Wasik¹

• ¹Department of Medical Microbiology, Faculty of Medical Science in Katowice, Medical University of Silesia, Katowice, Poland
• ²Division of Molecular Bacteriology, Medical University of Gdańsk, Gdańsk, Poland
• ³Intercollegiate Faculty of Biotechnology, University of Gdańsk, Gdańsk, Poland
• ⁴Leiden University Center for Infectious Diseases and Dutch National Expertise Center for Clostridioides difficile, Leiden University Medical Center, Leiden, Netherlands
• ⁵Department of Medical Microbiology, Medical University of Warsaw, Warsaw, Poland
• ⁶Leiden University Center for Infectious Diseases and Dutch National Expertise Center for Clostridioides difficile, Leiden University Medical Center,, Leiden, Netherlands
• ⁷Department of Medical Microbiology, Faculty of Pharmaceutical Sciences in Sosnowiec, Medical University of Silesia, Katowice, Poland

Introduction: Toxigenic strains of Clostridioides difficile are the leading cause of healthcare-associated bacterial infections in Poland. In the Silesian Voivodeship, with 4.5 million inhabitants, the incidence of C. difficile infection (CDI) in 2023 reached 65.1/100,000, slightly down from 70.0/100,000 in 2022. This study aimed to investigate the occurrence of toxigenic C. difficile ribotypes in hospitalized patients in Silesia. Material and Methods: A total of 130 stool samples from patients with confirmed antibiotic-associated diarrhea were tested. Multiplex PCR detected genes for GDH, toxins A/B, binary toxin CDT, and 16S rDNA. Ribotyping was performed by capillary PCR, and antibiotic susceptibility was tested with ETEST for 10 antibiotics. Results: Multiplex PCR confirmed the presence of all toxins (A+B+CDT+) in 97 isolates. Six strains (6%) represented ribotype 955 (RT955), first reported in Poland in 2023. RT027 remained dominant (60%, n=78). All isolates were susceptible to vancomycin, while 4% (5/130) showed metronidazole resistance. Conclusion: RT027 remains prevalent among CDI cases in Silesia. The emergence of RT955, closely related to a UK epidemic strain, suggests a possible shared origin and epidemiological link.