关键词: 山羊；混合感染；山羊支原体山羊肺炎亚种；大肠埃希菌

Abstract: To identify the causative agent responsible for goat deaths on a large?scale farm in Lufeng City，Yunnan Province，lung tissue and tracheal secretion samples were collected from deceased animals. PCR was used for initial pathogen screening， followed by bacterial isolation， mycoplasma culture， morphological observation， biochemical identification，antimicrobial susceptibility testing，sequencing，and phylogenetic analysis. The results showed that samples were positive for Mycoplasma capricolum subsp. Capripneumoniae （Mccp）nucleic acid. One bacterial strain and one Mycoplasma strain were successfully isolated from lung tissue. The bacterial strain was identified biochemically as Escherichia coli，which was sensitive to colistin，kanamycin，gentamicin，apramycin， and nitrofurantoin. The Mycoplasma strain was confirmed by PCR amplification，yielding a a 670 bp target gene fragment with 100.00% sequence identity to the Mccp strain（GenBank accession number：CP144022.1）. These findings indicate that the mortality in goats on this farm was caused by mixed infection with Mccp and E. coli. This study provides a reference for the diagnosis，treatment，and control of infectious respiratory diseases in local goats in Yunnan.

Key words: Goat；Coinfection；Mycoplasma capricolum subsp. Capripneumoniae；Escherichia coli