Effect of tetracycline treatment regimens on antibiotic resistance gene selection over time in nursery pigs

Kaare Græsbøll,Øystein Angen,Inge Larsen,Anna Camilla Birkegård,John Elmerdahl Olsen,Jens Peter Nielsen,Lasse Engbo Christiansen,Anders Folkesson,Julie Clasen

doi:10.1186/s12866-019-1619-z

Kaare Græsbøll, Øystein Angen + Show 7 more

Open Access

https://doi.org/10.1186/s12866-019-1619-z

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Abstract

BackgroundThe majority of antimicrobials given during the production of pigs are given to nursery pigs. The influence of antimicrobial use on the levels of antimicrobial resistant (AMR) genes is important to quantify to be able to assess the impact of resistance on the food chain and risk to human and animal health.ResultsThis study investigated the response on the levels of nine AMR genes to five different treatment strategies with oxytetracycline, and the dynamics of gene abundance over time by following 1167 pigs from five different farms in Denmark.The results showed no significant difference between treatments and an increase in abundance for the efflux pump encoding tet(A) gene and the genes encoding the ribosomal protection proteins tet(O) and tet(W) tetracycline resistant genes following treatment, while tet(M) showed no response to treatment. However, it was also observed that the levels of tet(O), tet(W), and ermB in some farms would drift more over time compared to a single treatment-course with antibiotic.ConclusionThis study underlines the large variation in AMR levels under natural conditions and the need for increased investigation of the complex interactions of antimicrobial treatment and other environmental and managerial practices in swine production on AMR gene abundance.

Highlights

The majority of antimicrobials given during the production of pigs are given to nursery pigs
We study the impact of these different treatment regimens on the prevalence and levels of nine antimicrobial resistant (AMR) genes (ermB, ermF, sulI, sulII, tet(A), tet(B), tet(M), tet(O) and tet(W)) which are frequently present in pigs on Danish pig farms [37, 38] The aim of the present study was to determine the effect of five different oxytetracycline treatment regimens on a selection of AMR genes in the normal flora in nursery pigs in a randomized clinical field trial
Sample collection A total of five farms were included in the study, and samples were collected from a total of 1167 ear marked pigs. pigs received batch treatment with High Dose (HD), with Normal Dose (ND) and 224 with Low Dose (LD) of oxytetracycline (OTC). 241 pigs were included in the pen wise treatment group (PW), and 221 in the injection treatment group (IM)

Summary

Introduction

The majority of antimicrobials given during the production of pigs are given to nursery pigs. The intensive use of antibiotics in society in general, and in the food production systems in particular, may increase the chance of transmission of antibiotic resistant microorganisms to humans from livestock or the environment. Recent technological developments in molecular biology, have increased our ability to investigate and quantify the gene content of microbial communities without cultivation. This has enabled us to study to what extent the normal flora is affected by the use of Græsbøll et al BMC Microbiology (2019) 19:269 antimicrobials, and to detail the molecular ecology of AMR genes [21,22,23,24,25,26]

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