The characterization and pathogenicity of Morganella morganii strains isolated from beef cattle in Sichuan Province, China

Morganella morganii (M. morganii) is a member of the genera Morganella in the Enterobacteriaceae family. We tried to better understand the prevalence and characterization of M. morganii strains in cattle. A total of 191 nasal swab samples from beef cattle in Guang'an, Yibin, and Ziyang, Sichuan province, China were collected. The presence of M. morganii in the swabs was determined by PCR. Then positive swabs were processed using bacterial isolation and identification. The M. morganii isolates were assayed for antimicrobial susceptibility and pathogenicity using a mouse model. The prevalence of M. morganii in three cities was 10.5% (20/191). Three M. morganii strains (16GA7, 17GA61.2, and 17YB9) were isolated and identified from positive swab samples. Phylogenetic analysis demonstrated that the 16S rRNA gene of M. morganii isolates could be clustered with known Genbank M. morganii strains. All three M. morganii strains were sensitive to penicillin-type and quinolone antibiotics and were resistant to some cephalosporins, carbapenems, macrolide antibiotics and polymyxin B. Lesions in mice inoculated with M. morganii included pulmonary hemorrhage, thickened alveolar walls and pulmonary inflammatory cell infiltration, although lesions varied by strain. Through research on the M. morganii in beef cattle, it was found that mice were susceptible to M. morganii isolates. To the best of our knowledge, the present study is the first to report the prevalence of M. morganii in beef cattle.