C. canimorsus are normal commensal bacteria of the dog's oral microbiota that cause septicaemia to persons that have been in contact with a dog, with a frequency of about 4 cases per year and million inhabitants. The disease often evolves to a septic shock with peripheral gangrene. In spite of therapeutic amputations and adequate treatment, the mortality ranges between 18 and 40 % according to the studies. The disease is probably under-diagnosed because the growth of C. canimorsus is fastidious. For the same reason, the number of strains isolated from patients and available for research, worldwide, is very low. Our previous studies have shown that a small minority of dog-hosted C. canimorsus is more virulent for humans than the others. These strains can be identified by the kind of capsule they carry.
The proposal taken to proof of concept was to market a PCR test designed to identify the dogs carrying the more dangerous strains (capsular serovars) of C. canimorsus. The rationale is that the detection of potentially dangerous dogs could save human lives. Indeed, the persons in contact with a dog harbouring a virulent serovar could be secured by rigorous hygiene, by an immediate antibiotic treatment in case of bite or scratch and by a fast medical support when diffuse flu-like symptoms occur.
Before the test can be brought to the market, the prevalence of the dangerous serovars in strains isolated from human infections and from dog mouths had to be strengthened on a higher number of strains. With this POC, we could contact the University hospital of Helsinki who just published an excellent retrospective study of C. canimorsus human infections. In collaboration, we typed a great number of strains isolated from patients that were admitted in the intensive care unit, during a period of 10 years. The results showed that indeed all the pathogenic strains belong to the capsular serovars we had identified before.
To determine the sensitivity and the specificity of our proposed test, we analyzed the salivas of 285 different dogs by PCR and by classical bacteriology. The PCR test proposed initially failed because of a lack of specificity but we designed a new PCR test and we re-tested the 285 dogs salivas as well as 199 strains isolated from patients. The new test turned out to be specific and relatively sensitive. It will now be adapted for the machines generally used in clinical laboratories, with the help of a company.
