| Autor: |
Casagrande Proietti P; Department of Veterinary Medicine, University of Perugia, Via S. Costanzo 4, 06126 Perugia, Italy., Musa L; Department of Veterinary Medicine, University of Perugia, Via S. Costanzo 4, 06126 Perugia, Italy., Stefanetti V; Department of Veterinary Medicine, University of Perugia, Via S. Costanzo 4, 06126 Perugia, Italy., Orsini M; Istituto Zooprofilattico Sperimentale delle Venezie, 35020 Padova, Italy., Toppi V; Department of Veterinary Medicine, University of Perugia, Via S. Costanzo 4, 06126 Perugia, Italy., Branciari R; Department of Veterinary Medicine, University of Perugia, Via S. Costanzo 4, 06126 Perugia, Italy., Blasi F; Istituto Zooprofilattico Sperimentale dell'Umbria e Delle Marche 'Togo Rosati', 06124 Perugia, Italy., Magistrali CF; Istituto Zooprofilattico Sperimentale dell'Umbria e Delle Marche 'Togo Rosati', 06124 Perugia, Italy., Capomaccio S; Department of Veterinary Medicine, University of Perugia, Via S. Costanzo 4, 06126 Perugia, Italy., Kika TS; Faculty of Veterinary Medicine, Agricultural University of Tirana, 1029 Tirana, Albania., Franciosini MP; Department of Veterinary Medicine, University of Perugia, Via S. Costanzo 4, 06126 Perugia, Italy. |
| Abstrakt: |
This work aimed to evaluate phenotypically and genotypically the colistin susceptibility of 85 Salmonella Infantis strains isolated in Italy from the broiler production chain, and to apply a whole-genome approach for the determination of genes conferring antimicrobial resistance (AMR). All isolates were tested by the broth microdilution method to evaluate the colistin minimum inhibitory concentrations (MICs). A multiplex PCR was performed in all isolates for the screening of mcr-1 , mcr-2 , mcr-3 mcr-4 , mcr-5 genes and whole-genome sequencing (WGS) of six S . Infantis was applied. Three out of 85 (3.5%) S . Infantis strains were colistin resistant (MIC values ranged from 4 to 8 mg/L) and mcr-1 positive. The mcr-1.1 and mcr-1.2 variants located on the IncX4 plasmid were detected in three different colistin-resistant isolates. The two allelic variants showed identical sequences. All six isolates harbored blaCTXM-1 , aac(6')-Iaa and gyrA/parC genes, mediating, respectively, beta-lactam, aminoglycoside and quinolone resistance. The pESI-megaplasmid carrying tet(A) (tetracycline resistance), dfrA1 , (trimethoprim resistance) sul1 , (sulfonamide resistance) and qacE (quaternary ammonium resistance) genes was found in all isolates. To our knowledge, this is the first report of the mcr-1.2 variant described in S . Infantis isolated from broilers chickens. Our results also showed a low prevalence of colistin- resistance, probably due to a reduction in colistin use in poultry. This might suggest an optimization of biosecurity control both on farms and in slaughterhouses. |
