Detection of CTX-M-15 Extended-Spectrum β-Lactamases Producing <i>Escherichia coli</i> Isolates from Colostrum and Faeces of Newborn Dairy Calves in China

• Main Authors: Zhiyuan He, Sirui Yang, Yulin Ma, Shuyuan Zhang, Zhijun Cao
• Format: Article
• Language: English
• Published: MDPI AG 2021-09-01
• Series: Pathogens
• Subjects: dairy calves; colostrum; faeces; ESBL-EC; <i>bla</i>_CTX-M-15 gene; IncHI2 plasmid
• Online Access: https://www.mdpi.com/2076-0817/10/9/1162

Newborn dairy calves are often colonized by multidrug-resistant (MDR) extended-spectrum β-Lactamase producing <i>Escherichia coli</i> (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-<i>E. coli</i> has not been well-studied. Here, we report on similar antibiotic resistance patterns of <i>E. coli</i> 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 <i>bla</i>_CTX-M-15 and <i>bla</i>_TEM-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 <i>bla</i>_CTX-M-15 and <i>bla</i>_TEM-171 genes, and isolated from faeces and the colostrum stock fed to the dairy calves.