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Published on: February 23, 2014
Human case of bacteremia caused by Streptococcus canis sequence type 9 harboring the scm gene
Daisuke Taniyama1, Yoshihiko Abe2, Tetsuya Sakai1
1Department of General Internal Medicine, Tokyo Saiseikai Central Hospital, Tokyo, Japan.
Abstract:
Streptococcus canis (Sc) is a zoonotic pathogen that is transferred mainly from companion animals to humans. One of the major virulence factors in Sc is the M-like protein encoded by the scm gene, which is involved in anti-phagocytic activities, as well as the recruitment of plasminogen to the bacterial surface in cooperation with enolase, and the consequent enhancement of bacterial transmigration and survival. This is the first reported human case of uncomplicated bacteremia following a dog bite, caused by Streptococcus canis harboring the scm gene. The similarity of the 16S rRNA from the infecting species to that of the Sc type strain, as well as the amplification of the species-specific cfg gene, encoding a co-hemolysin, was used to confirm the species identity. Furthermore, the isolate was confirmed as sequence type 9. The partial scm gene sequence harbored by the isolate was closely related to those of other two Sc strains. While this isolate did not possess the erm(A), erm(B), or mef(A), macrolide/lincosamide resistance genes, it was not susceptible to azithromycin: its susceptibility was intermediate. Even though human Sc bacteremia is rare, clinicians should be aware of this microorganism, as well as Pasteurella sp., Prevotella sp., and Capnocytophaga sp., when examining and treating patients with fever who maintain close contact with companion animals.
Insights
This report details the first human bacteremia case from Streptococcus canis (Sc) after a dog bite. The infection involved the M-like protein (scm) gene, highlighting zoonotic risks from companion animals.
Area of Science:
- Microbiology
- Zoonotic Diseases
- Infectious Diseases
Background:
- Streptococcus canis (Sc) is a zoonotic pathogen transmitted from companion animals.
- The M-like protein (scm gene) is a key virulence factor in Sc, aiding bacterial survival and spread.
- Human Sc infections are rare, but potential risks exist, especially after animal bites.
Purpose of the Study:
- To report the first human case of uncomplicated bacteremia caused by Streptococcus canis following a dog bite.
- To characterize the infecting Sc isolate, including its virulence genes and antimicrobial susceptibility.
- To raise clinical awareness of Sc as a potential pathogen in patients with animal contact.
Main Methods:
- Species identification using 16S rRNA gene sequencing and amplification of the species-specific cfg gene.
- Genotyping of the isolate using sequence typing (ST9).
- Analysis of the scm gene sequence and screening for macrolide/lincosamide resistance genes (erm(A), erm(B), mef(A)).
- Antimicrobial susceptibility testing, including azithromycin.
Main Results:
- The first documented human case of uncomplicated bacteremia due to Streptococcus canis after a dog bite.
- The isolate carried the virulence-associated scm gene, with its sequence closely related to other Sc strains.
- The isolate was identified as sequence type 9 and possessed the cfg gene.
- While lacking common macrolide resistance genes, the isolate showed intermediate susceptibility to azithromycin.
Conclusions:
- Clinicians should consider Streptococcus canis in patients presenting with fever after close contact with companion animals, particularly following bites.
- The presence of the scm gene in this human isolate underscores its potential role in zoonotic infections.
- Awareness of other potential pathogens like Pasteurella, Prevotella, and Capnocytophaga is also crucial in managing such cases.
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