Molecular epidemiological analyses of Clostridioides difficile isolates in a university hospital in Japan.

Background: We performed molecular epidemiological analyses of Clostridioides difficile isolates in a university hospital in Japan to reveal the risk of C. difficile infection. Methods: Cultured isolates from 919 stool samples from 869 patients obtained from July 2015 to August 2016 were subjected to toxin gene detection, ribotyping, multilocus sequence typing, antimicrobial susceptibility testing, and quantitative real-time polymerase chain reaction testing for C. difficile toxin gene expression. Results: Of the 919 stool samples from 869 patients, C. difficile was isolated from 153 samples (16.6%), of which 49 (32%) and 104 (68%) were from patients with and without C. difficile infection, respectively. Analyses showed genetic diversity, with ST8 and ST17 strains of healthcare-associated infections, some of which caused C. difficile infections. There was no significant difference in the transcription levels of C. difficile toxin genes between isolates from patients with and without C. difficile infection. Conclusions: Major Japanese clonal strains, ST8 and ST17, have been in the hospital environment for a long time and cause healthcare-associated C. difficile infections. The C. difficile toxin genes were transcribed in the isolates from both patients with and without C. difficile infection but were no significant relationship with the development of C. difficile infection.

Evaluation of a novel Clostridioides difficile-selective growth broth under aerobic conditions.

A newly developed Clostridioides difficile-selective growth broth, which can be cultured under aerobic conditions, was found to have a sensitivity/specificity (98%/89%) comparable to conventional anaerobic culture methods. This might be a powerful tool for diagnosing Clostridioides difficile infection in resource-limited regions and health care settings in the future.

Whole-Genome Sequencing Analysis of blaNDM-5/IncX3 Plasmid Estimated to Be Conjugative-Transferred in the Gut.

We characterized plasmids carrying blaNDM-5 detected in Escherichia coli isolated from the infection site and stool sample of a Japanese patient, with no international travel history, by whole-genome sequencing (WGS). WGS was performed using MiSeq and MinlON sequencer followed by hybrid de novo assembly. blaNDM-5 was detected on IncX3 (blaNDM-5/IncX3) plasmids; pMTY18530-4_IncX3 in E. coli TUM18530 isolated from a wound above the pubis; pMTY18780-5_IncX3 and pMTY18781-1_IncX3 in E. coli TUM18780 and TUM18781, respectively, isolated from stool. These three plasmids resembled each other and pGSH8M-2-4, previously detected in E. coli isolated from a Tokyo Bay water sample. E. coli TUM18530 and TUM18780 belonged to sequence type (ST) 1011 and had only two single nucleotide polymorphisms on the core-genome, whereas TUM18781 belonged to ST2040. Three blaNDM-5/IncX3 plasmids (pMTY18530-4_IncX3, pMTY18780-5_IncX3, and pMTY18781-1_IncX3) exhibited conjugative transfer in vitro at an average frequency of 1.71 × 10-3 per donor cell. The transconjugant was resistant to only ß-lactams, including carbapenem, except aztreonam. Similarity of the blaNDM-5/IncX3 plasmids isolated from our patient compared with that isolated from the Tokyo bay water sample suggested that the plasmids may have already spread throughout the Japanese community. The blaNDM-5/IncX3 plasmid exhibited potential for easy transmission to different strains in the patient's intestine.