Detection of CTX-M-15 Extended-Spectrum β-Lactamases Producing Escherichia coli Isolates from Colostrum and Faeces of Newborn Dairy Calves in China
Zhiyuan He, Sirui Yang, Yulin Ma, Shuyuan Zhang, Zhijun Cao
Abstract
Newborn dairy calves are often colonized by multidrug-resistant (MDR) extended-spectrum β-Lactamase producing Escherichia coli (ESBL-EC), which pose significant risks to global healthcare. As the first meal of calves, the role of dairy colostrum as a potential source of MDR-E. coli has not been well-studied. Here, we report on similar antibiotic resistance patterns of E. coli strains, isolated from colostrum fed to dairy calves and their faeces. Four ESBL-EC strains from colostrum and faeces of newborn dairy calves were isolated by double-disc synergy testing and multiplex PCR. Strikingly, isolates from colostrum or faeces were found to have similar MDR profiles, showing a high resistance to cephalosporins and other conventional antibiotics. In addition, coexistence of blaCTX-M-15 and blaTEM-171 was detected on a self-transferable plasmid with a typical IncHI2 backbone. To the best of our knowledge, this is the first case reporting on ESBL-EC strains carrying blaCTX-M-15 and blaTEM-171 genes, and isolated from faeces and the colostrum stock fed to the dairy calves.