Diversity of tetracycline resistant genes in Escherichia coli from human and environmental sources

Worldwide tetracycline resistance (Tc^r) is increasing dramatically,causing serious environmental and health problems. A total of 201 samples were collected from chicken intestine,human feces and treated sewage effluent (TSE). One hundred and eighteen Escherichia coli strains were isolated and identified using MALDI-Biotyper. Single and multiplex PCR were used to screen isolates for 14 tet genes,among which only 7 tet genes (A,B,C,M,Q,W,32) were found. Among the resistant isolates,tet A was the most frequent gene,followed by tet B and tet 32 while the rest of tet determinants occurred at a lower frequency. Many strains contained multiple Tc^r determinants. Some strains contained 4 tet gene-combination,tet (A/B/C/32) and tet (A/B/M/32). The 4 tet gene combination is reported for the first time in this region. The Tcr isolates showed a high variation of tet gene combination. The increase in the resistance of tetracycline with high diversification is an indication of antibiotics overuse. Strict enforcement of regulation is urgently needed to control and prevent the spread of tetracycline resistant strains which are detrimental to the environment.