Abstract: [Objective] To determine the causive agent of calf diarrhea in a family livestock farm in New Barag Right Banner of Hulun Buir City, Inner Mongolia, and to provide references for drug selection for treatment of calf diarrhea in this farm. [Method] Diseased calves′ anal swabs were obtained aseptically for bacterial culture, identification and in vitro antimicrobial sensitivity test. [Result] A bacterial strain was isolated from the anal swab samples of the diarrhea calves. The colonies were similar in morphology in the culture. The strain was identified as Providencia rettgeri by Gram′s staining, physiological and biochemical identification, and 16S rDNA sequence analysis. It was resistant to aztreonam, ceftazidime, cefotaxime, cefepime, ceftriaxone, tetracycline, chloramphenicol, and furantoin, moderately sensitive to ampicillin and gentamicin, and sensitive to cefoxitin, streptomycin, piperacillin, amikacin, ofloxacin, norfloxacin, and levofloxacin. [Conclusion] Providencia rettgeri is the causive agent of calf diarrhea in this farm. For clinical treatment, streptomycin is recommended.

Key words: Providencia rettgeri, calf, isolation and identification