Detection of beta-lactam resistance genes in swine, soil and wastewater isolates from a production unit

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Abstract

Beta-lactam antibiotics, such as cephalosporins, are widely used in pig farming to treat respiratory diseases and gastrointestinal disorders, and also for the prophylaxis against bacterial infections in weaned piglets. Carbapenems, in turn, are not licensed for use in swine, but are used in hospital settings to treat multidrug-resistant infections caused by Gram-negative bacteria. However, there are reports of resistance to carbapenems in non-hospital environments, such as livestock, food-producing animals, wastewater and soil. The main mechanism of resistance against beta-lactams among Gram-negative bacteria is hydrolysis of the antibiotic molecule through enzymes called beta-lactamases. Previous studies have shown a high frequency of resistance to these antibiotics in swine, soil and wastewater. Therefore, the aim of this work was to investigate the presence of genes associated with carbapenem resistance and ESBL production in the isolates. For this, the phenotypic profile of 131 bacterial carbapenem-resistant isolates (29 from swine, 58 from soil and 44 from wastewater) was determined and a molecular analysis was performed to screen for the following genes: blaCTX-M, blaKPC, blaOXA-48, blaNDM, blaVIM, blaIMP. Gene detection was performed by conventional PCR using primers listed in the literature. The presence of genes associated with resistance to beta-lactams (blaCTX-M, blaVIM and blaIMP) was observed, and 85% of the isolates from the three environments carried at least one resistance determinant. The blaVIM gene was the most frequent among soil isolates (65%), followed by blaCTX-M (58%), in addition to two isolates that also carried the blaIMP gene simultaneously. In wastewater, the blaVIM gene was present in 70% of the isolates, followed by the blaCTX-M gene (42%). In the swine isolates blaCTX-M was the most frequent gene (76%), followed by blaVIM (34%). The probability of an isolate carrying the blaCTX-M gene was 54%, while the probability of the isolate carrying the blaCTX-M and blaVIM genes simultaneously was 95%. Our study suggests a possible cross-resistance between cephalosporins and carbapenems mediated by resistance determinants associated with Gram-negative bacteria recovered from swine, soil and wastewater. Furthermore, we demonstrated that genes that confer resistance to cephalosporins and carbapenems are widely distributed among the three environments, even without a history of these antibiotics being used in the pig farm.

Institutions
  • 1 Departamento de Microbiologia / Centro de Ciências Biológicas e da Saúde / UFV - Campus Viçosa (Universidade Federal de Viçosa - Campus Viçosa)
Track
  • Microbiologia Veterinária
Keywords
beta-lactamase
cross-resistance
livestock