Emergence of Clostridium difficile tcdC variant 078 in Marseille, France.

The purpose of this investigation was to evaluate the epidemiology of hypervirulent Clostridium difficile ribotypes from January 2013 to February 2017 in the Marseille area of southern France. By using the Xpert Clostridium difficile Epi polymerase chain reaction (PCR) assay and sequencing the tcdC gene, we characterised C. difficile isolates from symptomatic patients diagnosed with C. difficile infection (CDI) in Marseille university hospitals. We first tested retrospectively 278 C. difficile samples isolated from January 2013 to December 2014 and observed a high prevalence of isolates with tcdC mutations and deletions previously described in both hypervirulent ribotypes RT027 and RT078 (16.4% and 10.7%, respectively). We highlighted the co-circulation of these two hypervirulent C. difficile tcdC variants (tV) with distinct epidemiological characteristics. While an RT027 outbreak occurred mainly as healthcare-associated infection in the elderly, CDI caused by tV078 occurred mainly in a younger population as community-associated infection. From January 2016, a systematic survey of these two hypervirulent C. difficile ribotypes revealed the emergence of CDI caused by tV078, currently being more prevalent than RT027 in the Marseille area. The present study is the first report of the emergence of CDI caused by tV078 in southern France. We showed the simultaneous circulation and sequential spread of hypervirulent ribotypes, such as RT027 and tV078. This emphasises the need for an efficient surveillance system for CDI with ribotyping and an optimised management of CDI caused by hypervirulent strains.

Careful use of 16S rRNA gene sequence similarity values for the identification of Mycobacterium species.

In order to evaluate the suitability of 16S rRNA nucleotide sequence similarity for the classification of new Mycobacterium isolates at the species level, we systematically studied the pairwise identity values of this gene for 131 Mycobacterium species with standing in nomenclature. Only one of the studied species, M. poriferae (0.76%), strictly respected the 95% and 98.65% threshold values currently recommended to determine the affiliation of bacterial isolates to an existing or new genus or species, respectively. All other species exhibited at least an identity value >98.65% and/or <95% with another Mycobacterium species. Therefore, we suggest that interpretation of interspecies 16S rRNA identity values should be made cautiously when classifying a new mycobacterial isolate at the species level.