Abstract:

In order to identify the causative agent of sudden death of guinea pigs at a farm, clinical observation, pathological dissection and bacterial isolation were conducted on guinea pigs suspected of bacterial infection. Gram staining, 16S rDNA sequencing and antimicrobial susceptibility test were performed following bacterial isolation. The results showed that the same pathogenic bacteria could be isolated from multiple organs of dead guinea pigs, which had obvious β- hemolytic rings, Gram positive staining, and were arranged in pairs or short chains. The 16S rDNA sequence of the isolated bacterial strain had a high homology of 99.77% with that of Streptococcus equi subsp. zooepidemicus (MK614224). The results of antimicrobial susceptibility test showed that the isolated bacterial strain was sensitive to 4 drugs, including ceftiofur and doxycycline; Moderate sensitivite to erythromycin and ciprofloxacin; Resistant to 15 drugs including cefotaxime and penicillin. The results of this experiment confirmed that Streptococcus equi subsp. zooepidemicus was the pathogen causing sudden death of guinea pigs, and the isolated strain showed strong drug resistance, providing a reference for the prevention and control of Streptococcus equi subsp. zooepidemicus.

Key words: guinea pig, Streptococcus equi subsp. zooepidemicus, isolation and identification, drug resistance