Occurrence of antibiotic resistant bacteria and resistance genes in agricultural irrigation waters from Valencia city (Spain)

The increasing use of antibiotics has become one of the main environmental and health problems today, worldwide. In addition to causing toxic effects on non-targeted organisms, their presence in the environment promotes the horizontal transfer of resistance genes, thus increasing the presence of resistant bacteria in the environment and, consequently, the risk of super-resistant bacterial infections. In the present work, we have investigated the occurrence of antibiotic-resistant E. coli and genes (blaTEM, qnrS, tetW, sulI and ermB) in surface water samples from different agricultural irrigation ditches located around Valencia city (Spain). Results of the research showed the presence of antibiotic resistance genes in all the analysed samples with mean percentages of 100% for tetW, 96% for blaTEM, 80% for sulI, 72% for qnrS and ermB in 60% of samples. The higher antibiotic resistance rates were detected in the samples whose waters had more contact with human or animal activities. Our study detected a high proportion (79.2%) of multi-resistant E. coli isolates, which presented a total of 26 multi-resistance patterns. The high levels of antibiotic resistances in irrigation waters observed in this work could help to both, better understanding and management, of the contamination caused by antibiotics and related resistance genes in agricultural environments, in order to implement appropriate measures for control. Moreover, appropriate surveillance of the quality of these waters as well as developing sanitation techniques are necessary to decrease antibiotic resistance rates in irrigation water in our geographical area.