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 investigated the resistance of 164 E. coli isolates (from Beijing, Tianjin, Inner Mongolia, Shanxi, and Hebei regions of China) to commonly used clinical sulfonamide antibiotics using a drug susceptibility test. The results show that the rates of resistance to sulfamonomethoxine and sulfamethoxazole-trimethoprim were 90.24% (148/164) and 73.17% (120/164), respectively. To explore 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 because of the existence of resistance genes, but other resistance mechanisms may also contribute to tolerogenesis.