PurposeTo determine the cause of diarrhea and death of calves in a cattle farm.
MethodA dominant strain was isolated from the pathological samples of causing diarrhea and even death of calves and analyzed by morphological characteristics, biochemical test, 16S rRNA genetic analysis, mouse pathogenicity test and drug susceptibility test.
ResultThe isolates were short rod-shaped or filamentous gram-negative bacteria. Except that the biochemical results of glucoside and malonate were “+”, the other biochemical characteristics were consistent with that of Proteus mirabils; the 16S rRNA sequence shares 100% homology with the P. mirabilis sequence in NCBI. The results showed that the isolated strain was P. mirabilis and named SS-1. SS-1 has strong pathogenicity, intraperitoneal injection of 2.9×109 CFU/mL bacterial solution 0.2 mL, 6 strains of SPF Kunming mice all died within 24 h, dissection showed cardiac effusion, pulmonary hemorrhage, liver congestion, swelling, intestinal congestion, thinning of the intestinal wall, and a large amount of yellow transparent mucous contents in the intestine; histopathology changes include pulmonary hemorrhage, hepatic, spleen, and kidney congestion, and inflammatory cell infiltration; drug sensitivity test results showed that SS-1 had special drug resistance, only sensitive to penicillin partial antibiotics such as ampicillin, aminoglycoside antibiotics such as amikacin, quinolones antibiotics such as ofloxacin, and cephalosporins antibiotics such as cefoperazone; it can be resistant to lincoa, tetracyclines, carbapenem and macrolides.
ConclusionThe SS-1 isolated from cows with diarrhea disease has some differences in biochemical characteristics, drug sensitivity characteristics and pathogenicity in mice from the previous reports of P. mirabilis, indicating that the bacteria may be mutated to increase the virulence, which caused the cow important pathogenic bacteria of diarrhea and even death should be highly regarded.
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