Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2021

Genomic Insights into the Zoonotic Transmission of Clostridioides difficile Sequence Type 35 Reveals a Clone of Emerging One Health Importance (#109)

Yun Luo 1 , Guangzhong Song 2 , Jun Yang 2 , Xiaojun Song 3 , Shan Lin 2 , Qian Liang 4 5 , Linli Sun 4 5 , Yi-Wei Tang 6 , Dazhi Jin 2 3
  1. School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
  2. School of Laboratory Medicine, Hangzhou Medical College, Hangzhou, Zhejiang, China
  3. Centre of Laboratory Medicine, Zhejiang Provincial People’s Hospital, People’s Hospital of Hangzhou Medical College, Hangzhou, Zhejiang, China
  4. Key Laboratory of Microorganism technology and bioinformatics research of Zhejiang Province, Hangzhou, Zhejiang, China
  5. NMPA Key Laboratory For Testing and Risk Warning of Pharmaceutical Microbiology, Hangzhou, Zhejiang, China
  6. Cepheid, Danaher Diagnostic Platform, Shanghai, China

Background

Clostridioides difficile sequence type (ST) 35 has been reported as one of the predominant genotypes associated with diarrhea in hospitalized patients, but is rarely found colonizing animals. It is still questionable whether ST35 causes zoonotic C. difficile infection.

Methods

We performed whole sequencing and high-resolution core genome phylogenetics on 123 isolates of C. difficile ST35 from both human and piglet origin in Asia, North America, Europe, and Australia. Virulence and antimicrobial resistance genes, PCR ribotyping (RT), toxin concentration, and sporulation capacity were also analyzed.

Results

C.difficile ST35 has two main genotypes, RT046 and RT220. Phylogenetic analysis presented two genetically distinct evolutionary clonal groups, clonal group1 (CG1) and clonal group2 (CG2), both of which were almost in accordance with RT types. Few virulence loci were found in ST35 genomes except tcdA and tcdB. Antimicrobial resistance elements were widely distributed with mainly tetM, ermB, blaCDD-1, APH (2'')-Ih, and van cassettes, but catD, aadE, gyrA and rpoB mutations existed in CG1. Core genome single-nucleotide polymorphisms (SNPs) analysis found one human strain showed a closely genetic relationship (separated by < 10 SNPs in their core genomes) with six animal strains from different farms spreading across interspecies in Sub-CG comprised of RT220 under CG2. These strains were obtained less than 124 apart in the same county with a direct epidemiological link, indicative of possible zoonotic transmission. Additionally, ST35 produced significantly stronger sporulation capacity than other STs did (Z=-8.12 and -7.75, P<0.001), but no difference among different origins (Z=-1.77, P=0.077).

Conclusion

This study provides novel insights into the phylogenetic evolution and genetic diversity of C. difficile ST35, revealing a clone of emerging One Health importance. The strong sporulation capacity enables ST35 to be easily spread among interspecies and transmitted zoonotically from piglets in China.