Comparison of the performances and validation of three methods for Yersinia spp. detection from animals stools samples in Abidjan: a non-endemic and a tropical area
Objective: Animals are the main reservoir for human enteropathogenics Yersinia. The aim of this survey was to compare the performances through three methods for detection of Yersinia enterocolitica 2/O: 9 and 1A/O: 14 bioserotypes in animals faecal samples contaminated in an artificial way and to validate the most efficient on animals samples from a tropical area.
Methods and results: The compared methods were the direct plating of samples on selective agar CIN, (M1) the cold enrichment at +4°C) in PBS (Phosphate-buffered saline), (M2) and the prior-enrichment at 25°C in a BCC broth containing 2.5 mg / l of novobiocin followed by an enrichment modified PBS supplemented with 1% mannitol, 0.15% of bile salts, 0.5% of soy peptone (M3). These methods respectively had a sensitivity of 0.66, 0.73 and 0.88 on the non-pathogenic strain 1A/O: 14 and 0.54, 0.59 and 0.78 on the pathogenic strain 2/O: 9. The negative predictive value was 0.39, 0.45 and 0.65 respectively. The limit of detection of the two enrichment methods was 102 CFU ml-1 versus 103 CFU ml-1 for the direct plating. When detection rates of these methods were compared, it was observed that a significant difference on the one hand between the direct plating and the PBS modified and on the other hand between the enrichment in the cold weather and the PBS modified. No significant difference has been observed between the direct plating and the cold enrichment in Phosphate-buffered saline. It has been observed that no method encouraged significantly the detection of one of the two reference strains.The validation of the enrichment methods out of 496 samples showed that only the method of M3 enrichment permitted isolation of two strains of Yersinia intermedia, biotype 4, serotype 7,8-8-8,19 in piglets’ faeces.
Conclusion: It appears from this study that the prior-enrichment at 25 ° C in a Brain Heart Infusion broth containing 2.5 mg / l novobiocin followed by a modified PBS (Phosphate-buffered saline) enrichment are appropriate methods for monitoring the epidemiology of enteropathogenics Yersinia in the animal faecal samples.
Key words: Yersinia enterocolitica, Livestock animals, faecal samples, Methods of detection, sensitivity, limit of detection