Performances of the BD MAX™ CDIFF assay for the detection of toxigenic Clostridioides difficile using Cary-Blair preserved samples.

Toxigenic Clostridioides difficile infection (CDI) is a high concern because of its increasing prevalence, among both nosocomial infection and community-acquired infection contexts. A total of 1320 prospective stool samples collected on FecalSwab™ (Cary-Blair medium) were screened using BD Max™ CDIFF assay (BDM). Results were compared to the routine algorithm including immunochromatographic testing for glutamate dehydrogenase (GDH) and toxin A/B (tox) using C. DIFF QUIK CHEK COMPLETE® followed by Xpert C. difficile assay in case of GDH+/tox- results. The prevalence of toxigenic C. difficile was estimated to 5.3% (n=70/1320) using the routine algorithm but to 7.4% (n = 98/1320) using BDM. The overall agreement between BDM and the routine algorithm was 97.4%. After resolution of discrepant results between BDM and the algorithm using Xpert C. difficile assay (unless already perform) and toxigenic culture performed by the French National Reference Laboratory, the overall agreement was increased to 99.4%, demonstrating the excellent performances of the test.

Influence of operating conditions on the persistence of E. coli, enterococci, Clostridium perfringens and Clostridioides difficile in semi-continuous mesophilic anaerobic reactors.

This study examined the combined effect of hydraulic retention time (HRT), organic loading rate (OLR) and heat pretreatment of manure (70 °C, 1 h) on the fate of E. coli, enterococci, C. perfringens, C. difficile, and on chemical parameters (volatile fatty acids and ammonia) that may inactivate pathogens. Semi-continuous mesophilic anaerobic reactors were fed with pig manure and horse feed. The operating conditions were 2, 3, 4 COD.L-1.d-1 (OLR), 24, 35, 46 days (HRT) and use or not of a thermal pretreatment. The levels of the chemical parameters did not reach concentrations capable of inactivating the four bacteria. Anaerobic digestion led to a Log10 removal > 3 (E. coli), 0.9-2.1 (enterococci), 0.1-0.6 (C. perfringens) and 0-1 (C. difficile). Increasing HRT only reduced the concentration of E. coli in the digestate. Increasing OLR reduced the Log10 removal of enterococci and C. difficile. The heat pretreatment led to non-detection of E. coli in the digestate, reduced the concentration of C. perfringens by 0.8-1.3 Log10 and increased the concentration of C. difficile by 0.04-0.7 Log10. Enterococci, not detected in the heated manure, were present in the digestate. The distribution of genes encoding virulence factors of C. difficile (tcdA and tcdB) and C. perfringens (cpa, cpb2 and cpb) was not impacted by anaerobic digestion or by the heat pretreatment. Enterococci, C. perfringens, C. difficile were present in the digestate at relatively stable concentrations regardless of the operating conditions, indicating that even with heat pretreatment, the biosafety of digestate cannot be guaranteed in mesophilic conditions.