Characterization of Clostridium difficile PCR-ribotype 018: A problematic emerging type.

Recent surveys indicate that the majority of toxigenic Clostridium difficile strains isolated in European hospitals belonged to PCR-ribotypes (RTs) different from RT 027 or RT 078. Among these types, RT 018 has been reported in Italy and, more recently, in Korea and Japan. In Italy, strains RT 018 have become predominant in the early 2000s, whereas the majority of strains isolated before were RT 126, a type belonging to the same lineage as the RT 078. In this study, we have found that Italian strains RT 018 are resistant to erythromycin, clindamycin, moxifloxacin and rifampicin. Rifampicin resistance is rarely observed in strains RT 018 from other countries and in Italian strains RT 078 and RT 126, therefore the decennial use of rifamycin antibiotics in Italy may be one of the driving factors for the spread of RT 018 in our country. The strains RT 018 examined showed a significant higher adhesion to Caco-2 cells compared to strains RT 078 and RT 126. Furthermore, strains RT 018 became predominant in in vitro competition assays with strains RT 078 or RT 126. If maintained in vivo, these characteristics could lead to a rapid colonization of the intestine by strains RT 018. Under the conditions used, isolates RT 018 produced significantly higher toxins levels compared to strains RT 078 and RT 126, while heat-resistant CFUs production seems to be strain-dependent. Robust toxin production and enhanced sporulation could in part explain the high diffusion and interpatient transmissibility observed for strains RT 018 in the hospital environment. In conclusion, the characteristics observed in the Italian isolates RT 018 seem to contribute in conferring an adaptive advantage to these strains, allowing their successful spread in our country.