A survey of the frequency of aminoglycoside antibiotic-resistant genotypes and phenotypes in Escherichia coli in broilers with septicaemia in Hebei, China.

1. The aim of this study was to investigate the occurrence of aminoglycoside resistance and the prevalence of 6 important modifying enzyme genes, i.e. (strA, strB, aph(3')-IIa, aac(3)-IIa, aac(6')-Ib and ant(3")-Ia), in Escherichia coli strains in broilers with septicaemia in Hebei, China. 2. A total of 111 clinical isolates of E. coli were collected from 46 large-scale farms. Antimicrobial susceptibility tests, using the Kirby-Bauer disc diffusion method, were performed on all 111 isolates. In addition, all were screened for the presence of modifying enzyme genes using the polymerase chain reaction (PCR). 3. The results show that the rates of resistance were as follows: streptomycin: 97.3%, kanamycin: 97.0%, gentamicin: 95.5%, neomycin: 50.5%, amikacin: 46.0%, spectinomycin: 22.5%. Of the genes examined, strB (73.9%) was the most frequently identified gene in the phenotypic resistant isolates, followed in order by: ant(3")-Ia, aac(3)-IIa, aac(6')-Ib, aph(3')-IIa and strA. 4. It is concluded that aminoglycoside resistance in E. coli from broilers with septicaemia remains a serious problem in Hebei, China. This emphasises the need to ban the non-therapeutic use of antibiotics, discourage their misuse and to be continually vigilant by providing appropriate scientific and technological support for the poultry industry.