Tetracycline resistance in Escherichia coli isolated from surface and wastewater from Tamaulipas, Mexico

Antibiotic resistance represents a threat to global health that increases morbidity and mortality in the population. The excessive and indiscriminate use of antibiotics has led to the emergence and spread of resistant bacteria. Tetracyclines have been one of the most widely used antibiotics because of their broad spectrum and low cost; they are frequently found in aquatic environments because of their low mobility and persistence in such sources. Therefore, the aim of this work was to evaluate tetracycline resistance in Escherichia coli strains isolated from surface water and wastewater in northeastern Tamaulipas, Mexico. In this study, 50 strains of E. coli were analyzed. Susceptibility testing showed that 54% of E. coli strains were resistant to tetracycline, of which 16 and 26% were resistant to minocycline and doxycycline, respectively. Resistance to streptomycin, ampicillin, and sulfamethoxazole-trimethoprim was also identified. Regarding the tet genes, tet (A) was the most prevalent at 74 %, while intI was found at 22 % (p > 0.05). In the conjugation assay, 41 % (11/25) of E. coli strains showed potential to transfer resistance to tetracycline, and only tet (A) was transferred to the recipients in 81 %, while intI was transferred in 27 %. Finally, E. coli strains isolated on the surface and wastewater of northeastern Tamaulipas represent a health and environmental risk because of the potential to spread their resistance in the aquatic environment and other environments and bacterial communities.