Caracterización de integrones y casetes de resistencia a antimicrobianos y amino cuaternarios en cepas de Salmonella aisladas en el Estado de México

Abstract

Salmonella spp, is a public and animal health problem, due to the emergence of multiresistant strains to antimicrobials, this multiresistance has been related to resistance genes that are found in the bacterial chromosome or related with plasmids, transposons and recently to integrons resistance; therefore, the first objective of the study was to determine the phenotypic and genotypic resistance to antibiotics of Salmonella spp. isolated from bovine animals carcasses sacrificed in slaughterhouses of the Center-North of Mexico State. The presence of PSE-1, tetG, qnrS, FloR, STR genes was determined. The isolates which identified these genes showed resistance to ampicillin, tetracycline, nalidixic acid, Florfenicol and streptomycin; however, some isolates that presented the resistance genes, did not express phenotypic resistance, this result was associated mainly to the fact that some genes do not contain a promoter in their coding region, which prevents its phenotypic expression; therefore, the second objective of this work was to characterize the class 1 integron of resistance in Salmonella spp. isolates of beef, sheep and poultry carcasses. The class 1 integron is composed of two conserved regions and a variable region where there are various resistance genes called genes cassette. The region 3'CS is composed of qacEΔ1 and sul1 genes, these genes confer resistance to quaternary amino compounds and sulfonamides respectively; however, variants have been identified for this region. We analyzed 77 isolates of Salmonella spp. obtained from pigs, poultry and cattle from slaughterhouses of the State of Mexico, Mexico. Forty percent of the isolates belonged to the class 1 integron, where the majority of these isolates showed “Caracterización de integrones y casetes de resistencia a antimicrobianos y amino cuaternario en cepas de Salmonella aisladas en el Estado de México” M en C. Jorge Antonio Varela Guerrero vi multidrug resistance to antibiotics such as streptomycin, ampicillin, tetracycline, gentamicin, chloramphenicol and trimethoprim-sulfamethoxazole. The cassette genes that were found, were dfrA17, dfrA12 of resistance to trimethoprim and genes aaA1, aaA2 and aaA5 of resistance to streptomycin. In the class 1 integron distal portion, we identified qacEΔ1/sul1; however, deletions in one or both of them was observed, the same as an unusual distal region composed of qacH and sul1 genes which confer the same resistance of qacEΔ1 and sul1 genes; but, with different origin that has not yet been explained. The different genotypic structures found in the present study indicate that the evolution of bacteria and their genetic and phenotypic adaptation to survive are factors that help the emergence of variants in the integrons, which could cause the antimicrobial therapy and disinfection does not have the expected results, by which increase the concern in global public health.