Emergence of a ribotype 244 strain of Clostridium difficile associated with severe disease and related to the epidemic ribotype 027 strain.
BACKGROUND
We identified 12 patients with Clostridium difficile infection between July 2011 and March 2012 from whom an unusual C. difficile strain was isolated. This strain had a single-nucleotide deletion of the tcdC gene at position 117 and binary toxin genes, which are characteristic of the hypervirulent ribotype (RT) 027 strain.


METHODS
A retrospective cohort study of 12 patients infected with C. difficile RT244 and 24 patients infected with non-RT244/non-RT027 strains matched for place of diagnosis and time of collection of specimen was performed. We performed whole-genome sequencing to understand the relationship of the RT244 strain to other C. difficile strains and further understand its virulence potential.


RESULTS
Clostridium difficile RT244 was associated with more severe disease and a higher mortality rate. Phylogenomic analysis using core genome single-nucleotide polymorphisms showed that RT244 is in the same genetic clade (clade 2) as RT027 but is distinct from all RT027 strains. The pathogenicity locus of the RT244 strain encodes a variant toxin B, and this was confirmed by demonstration of Clostridium sordellii-like cytopathic effect on Vero cells. Toxin B production in culture supernatants was lower than that seen with a RT027 strain.


CONCLUSIONS
Our findings demonstrate the pathogenic potential of this RT244 C. difficile strain and emphasize the importance of ongoing surveillance for emergent strains.
Monash Infectious Diseases, Monash Health.
Sze K
SK
Lim
Monash Infectious Diseases, Monash Health Department of Medicine, Southern Clinical School, Monash University.
Rhonda L
RL
Stuart
Department of Microbiology, Monash University.
Kate E
KE
Mackin
Department of Microbiology, Monash University.
Glen P
GP
Carter
Monash Infectious Diseases, Monash Health.
Despina
D
Kotsanas
Department of Microbiology, Monash Health, Clayton.
Michelle J
MJ
Francis
Microbiological Diagnostic Unit, University of Melbourne, Parkville.
Marion
M
Easton
Microbiological Diagnostic Unit, University of Melbourne, Parkville.
Karolina
K
Dimovski
School of Pathology and Laboratory Medicine, The University of Western Australia.
Briony
B
Elliott
School of Pathology and Laboratory Medicine, The University of Western Australia PathWest Laboratory Medicine, Nedlands.
Thomas V
TV
Riley
Microbiological Diagnostic Unit, University of Melbourne, Parkville.
Geoff
G
Hogg
School of Public Health and Preventive Medicine.
Eldho
E
Paul
Monash Infectious Diseases, Monash Health Department of Medicine, Southern Clinical School, Monash University Department of Microbiology, Monash Health, Clayton.
Tony M
TM
Korman
Victorian Bioinformatics Consortium, Monash University, Clayton.
Torsten
T
Seemann
Department of Microbiology and Immunology, University of Melbourne, Parkville, Australia.
Timothy P
TP
Stinear
Department of Microbiology, Monash University.
Dena
D
Lyras
Monash Infectious Diseases, Monash Health Department of Microbiology, Monash University Department of Microbiology, Monash Health, Clayton Department of Microbiology and Immunology, University of Melbourne, Parkville, Australia.
Grant A
GA
Jenkin
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001426:Bacterial Proteins / Q000235:genetics; D001427:Bacterial Toxins / Q000235:genetics; D016360:Clostridioides difficile / Q000235:genetics*; D021821:Communicable Diseases, Emerging / Q000453:epidemiology* / Q000382:microbiology*; D004196:Disease Outbreaks; D004761:Enterocolitis, Pseudomembranous / Q000453:epidemiology* / Q000382:microbiology*; D005260:Female; D016368:Frameshift Mutation; D016680:Genome, Bacterial; D006801:Humans; D008297:Male; D008875:Middle Aged; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide; D012097:Repressor Proteins / Q000235:genetics; D012189:Retrospective Studies; D021521:Ribotyping; D012720:Severity of Illness Index
D001426:Bacterial Proteins; D001427:Bacterial Toxins; D012097:Repressor Proteins; C105615:TcdC protein, Clostridium difficile; C031815:toxB protein, Clostridium difficile
Clostridium difficile; toxin B; virulence; whole-genome sequencing