Prevalence and Molecular Characterization of Extended-spectrum β–Lactamase - producing Escherichia coli Isolates from Dairy Cattle with Endometritis in Gansu Province, China

Background: The present study aimed to investigate the prevalence and molecular characterization of extended-spectrum β-lactamase ( ESBL )-producing Escherichia coli (E. coli ) isolated from dairy cattle with endometritis in China. The presence of ESBL-producing Escherichia coli in the sample was detected using ChromID ESBL agar, and genotyping of the ESBL producers was performed by PCR and DNA sequencing. Results: The results showed that 69.76% (180/258) of samples obtained from cows with clinical endometritis tested positive for pathogens, with E. coli accounting for 170 out of the 180 positive samples. The incidence rate of isolated E. coli infection was 39.14% (101/258), and co-infections with other pathogens were prevalent. Furthermore, among the 158 E. coli isolates, 50 (31.64%) were identified as producers of extended-spectrum beta-lactamases (ESBLs), with TEM and CTX-M prevalence rates of 78.00% and 32.00%, respectively. Drug sensitivity experiments indicated that the 50 ESBL-producing E. coli isolates were multidrug resistant, with 48.0% of them testing positive for both the class 1 integron gene and five gene cassettes responsible for resistance to trimethoprim (dfr1 and dfrA17) and aminoglycosides (aadA1, aadA5, and dfrA1), respectively. Conclusion: This investigation has demonstrated a substantial prevalence and elevated levels of antimicrobial resistance among ESBL-producing E. coli isolates derived from dairy cattle afflicted with endometritis in China.