Survey on sulfonamide antibiotic-resistant genotype and phenotype of avian Escherichia coli in North China

It is important for the prevention and treatment of colibacillosis to monitor drug resistance in Escherichia coli. To choose effective drugs to prevent and control avian colibacillosis in North China, we in- vestigated the resistance of 164 E. coli isolates (from Beijing, Tianjin, Inner Mongolia, Shanxi, and Hebei re- gions of China) to commonly used clinical sulfonamide antibiotics using a drug susceptibility test. The results show that the rates of resistance to sulfamonometh- oxine and sulfamethoxazole-trimethoprim were 90.24% (148/164) and 73.17% (120/164), respectively. To ex- plore the reasons for wide drug resistance, sulfonamide resistance genes were detected by PCR. Of the isolates, 90.85% (149/164) carried sulfonamide resistance genes. Therefore, resistance of avian E. coli to sulfonamide antibiotics is very serious in North China, perhaps be- cause of the existence of resistance genes, but other resistance mechanisms may also contribute to tolero- genesis.