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Tetracycline resistance tet(A) plasmids transferring multiresistance in enterotoxigenic E. coli strains from pigs.

Szmolka, Ama and Lestár, Barbara and Fekete, Péter Zsolt and Nagy, Béla (2013) Tetracycline resistance tet(A) plasmids transferring multiresistance in enterotoxigenic E. coli strains from pigs. In: 4th Central European Forum for Microbiology, October 16-18, 2013., Keszthely.

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Abstract

Enterotoxigenic E. coli (ETEC) bacteria are frequent pathogens causing watery diarrhea in weaned pigs. Plasmids encoding different enterotoxins (estA, estB, elt) and fimbrial adhesins (f4, f18) are of prime importance in the pathogenesis of ETEC strains. Recently, the complete sequence of the ETEC pTC plasmid was described, as a first representative of hybrid ETEC plasmids carrying the tetracycline resistance gene tet(B) in combination with enterotoxin genes estA and estB. Similarly, unraveling the impact of tet(A)-plasmids in the transfer of resistance and/or virulence would also be important for the efficient therapy of ETEC infections. The main objective of the present study was to provide a comparative description of antimicrobial resistance and virulence profiles of porcine post-weaning ETEC strains representing three middle-European neighboring countries: Hungary, Austria and the Czech Republic. Furthermore, the characterization of genetic vectors for tetracycline resistance was also attempted, with special regard to plasmids responsible for the transfer of tetracycline resistance gene tet(A) and putative co-resistance/virulence genotypes. A total of 87 porcine ETEC strains isolated from post-weaning diarrhea were included in this study. Majority of them were isolated in Europe: Hungary (n=16), Austria (n=34) and the Czech Republic (n=17), and 20 ETEC strains were derived from the USA. Antimicrobial resistance phenotype of the strains was determined for 17 antimicrobial compounds with clinical relevance. Strains resistant to tetracycline were subjected to further studies, including the PCR subtyping of the tet genes, and the detection and characterization of plasmids mediating tetracycline resistance and ETEC-specific virulence in two tet(A)-positive monoplasmidic derivatives of F18+ ETEC strains from Hungary and from the Czech Republic (2172/11 and 11732/71 respectively). Regardless of the geographical origin, majority of the ETEC strains shared a common MDR pattern of sulfamethoxazole (91%), tetracycline (84%) and streptomycin (80%) resistance. The tetracyclin resistant phenotype was most frequently covered by the presence of the tet(B) gene (38%), when tet(A) was identified in 26% of the isolates. The virulence gene profile included enterotoxin genes (elt, estA and/or estB), as well as adhesin genes (f4, f18) without geographic differences. Characterization of these tet(A) plasmids revealed, that the IncI1 plasmid of the Hungarian strain mediated the co-transfer of tet(A), aadA1 (streptomycin/spectinomycin) and strA (streptomycin) genes, when the IncF plasmid of the Czech strain carried tet(A) in association with catA1 for chloramphenicol resistance. Furthermore, the tet(A) plasmid of the Hungarian strain carried a class 1 integron with an unusual variable region of estX-aadA1 responsible to streptothricin-spectinomycin/streptomycin resistance phenotype. In conclusion, the presence of IncI1 and IncF type plasmids, responsible for the co-transfer of the tet(A) gene and additional resistance determinants were demonstrated for the first time in F18+ ETEC strains. In addition to the pTC hybrid plasmid of tet(B)-type, the first description of tet(A) plasmids was provided as a vector of multidrug resistance in porcine ETEC strains.

Item Type: Conference or Workshop Item (Lecture)
Subjects: S Agriculture / mezőgazdaság > SV Veterinary science / állatorvostudomány
Depositing User: PhD Ama Szmolka
Date Deposited: 19 Sep 2014 10:16
Last Modified: 03 Apr 2023 08:13
URI: http://real.mtak.hu/id/eprint/15468

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