Characterization Of Tetracycline Resistance Of Salmonella Enterica Subspecies Enterica Serovar Infantis Isolated From Poultry In The Northern Part Of Serbia

Dalibor Todorović,Ljiljana Suvajdžić,Maja Velhner,Dejan Vidanović,Igor Stojanov,Dubravka Milanov,Dejan Krnjaić

doi:10.1515/acve-2015-0046

Abstract

Abstract Resistance to tetracycline was studied in Salmonella Infantis isolated from 28 poultry farms in the Northern part of Serbia (The Autonomous Province of Vojvodina). A total of 18 isolates were resistant to nalidixic acid (NAL) and tetracycline (TET). The minimal inhibitory concentration (MIC) to TET, ranged from 1-256 mg/L. Namely, 13 isolates exhibited MIC to TET at 256 mg/L, in four of the isolates, the MIC was 128 mg/L and one isolate had MIC 64 mg/L. Ten isolates were exhibiting a MIC of 1mg/L. It was evident that Salmonella Infantis had also spread to breeders and layers. In this work, we detected the tetA gene and the corresponding tetR gene (encoding the repressor protein) as well as the truncated transposon Tn1721, which are responsible for the resistance to TET. The presence of the non conjugative transposons from the conjugative plasmid has facilitated the spread of resistance to TET in Salmonella. It was concluded that higher biosecurity practice in poultry farming presents the best option to eliminate infections caused by Salmonella spp. from poultry flocks in Serbia. A rational use of antimicrobials is necessary to prevent any further spread of Salmonella Infantis resistant clones.

Highlights

Salmonella is one of the most important food borne pathogens worldwide
Infantis isolated from poultry in the northern part of Serbia quinolones and TET were recently found in all types of commercial chickens i.e. broiler breeders, layer breeders, broilers and layer chickens 3
A single mutation on the gyrA gene Ser83→Tyr was found in the nalidixic acid resistant strains, while in isolates with an increased minimal inhibitory concentration (MIC) to ciprofloxacin (CIP) of 2 mg/L, additional mutations were found on parC gene at Ser80→Arg 2

Summary

Introduction

Infantis) in poultry production in Serbia is important. By applying pulse field gel electrophoresis, it was determined that strains resistant to NAL and TET are indistinguishable 1,2. Infantis isolated from poultry in the northern part of Serbia quinolones and TET were recently found in all types of commercial chickens i.e. broiler breeders, layer breeders, broilers and layer chickens 3. Infantis has to be minimized in poultry farms in Serbia. The mechanism of resistance to (fluoro) quinolones is attributed to the mutations on the topoisomerase genes encoding GyraseA and the topoisomerase IV enzymes. A single mutation on the gyrA gene Ser83→Tyr was found in the nalidixic acid resistant strains, while in isolates with an increased MIC to ciprofloxacin (CIP) of 2 mg/L, additional mutations were found on parC gene at Ser80→Arg 2

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