Spread of Antimicrobial Resistance by Salmonella enterica Serovar Choleraesuis between Close Domestic and Wild Environments.

María Gil Molino,Alberto Quesada,Sofía Gabriela Zurita,David Risco,Francisco Eduardo Martín-Cano,Waldo García-Jiménez,Pedro Fernández-Llario,Joaquín Rey,Alfredo García

doi:10.3390/antibiotics9110750

María Gil Molino, Alberto Quesada + Show 7 more

Open Access

https://doi.org/10.3390/antibiotics9110750

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Abstract

The Salmonella enterica serovar Choleraesuis affects domestic pig and wild boar (WB), causing clinical salmonellosis. Iberian swine production is based on a free-range production system where WB and Iberian pig (IP) share ecosystems. This study focuses on the negative impact on the pork industry of infections due to this serotype, its role in the spread of antibiotic resistance, and its zoonotic potential. Antibiotic resistance (AR) and genetic relationships were analyzed among 20 strains of S. Choleraesuis isolated from diseased WB and IP sampled in the southwest region of the Iberian Peninsula. AR was studied using the Kirby–Bauer method with the exception of colistin resistance, which was measured using the broth microdilution reference method. Resistance and Class 1 integrase genes were measured using PCR, and the genetic relationship between isolates and plasmid content by pulsed field gel electrophoresis. The results show a higher incidence of AR in isolates from IP. Phylogenetic analysis revealed seven profiles with two groups containing isolates from IP and WB, which indicates circulation of the same clone between species. Most pulsotypes presented with one plasmid of the same size, indicating vertical transmission. AR determinants blaTEM and tetA were routinely found in IP and WB, respectively. One isolate from IP expressed colistin resistance and presented the mcr-1 gene carried by a plasmid. This study suggests that S. Choleraesuis circulates between WB and IP living in proximity, and also that the mobilization of AR genes by plasmids is low. Furthermore, the detection of plasmid-mediated colistin resistance in bacteria from IP is alarming and should be monitored.

Highlights

Salmonellosis in swine results in tremendous economic losses in the pork industry [1].Salmonella enterica subsp. enterica serovar Choleraesuis
Choleraesuis is still very common in North America and Asia and, it is not considered a dominant serovar in pigs from Europe [4,5], different outbreaks have occasionally been reported in recent years [6,7] including in wild boar (WB) [2,3,8,9,10,11]
The Iberian pig (IP) is an autochthonous breed that originated in the Iberian Peninsula, for which the production system is mainly associated with extensive management deeply linked to the Mediterranean ecosystem and traditional agroforestry in the southwest of the Iberian Peninsula [12]

Summary

Introduction

Salmonellosis in swine results in tremendous economic losses in the pork industry [1].Salmonella enterica subsp. enterica serovar Choleraesuis Choleraesuis is still very common in North America and Asia and, it is not considered a dominant serovar in pigs from Europe [4,5], different outbreaks have occasionally been reported in recent years [6,7] including in WB [2,3,8,9,10,11]. The Iberian pig (IP) is an autochthonous breed that originated in the Iberian Peninsula, for which the production system is mainly associated with extensive management deeply linked to the Mediterranean ecosystem and traditional agroforestry in the southwest of the Iberian Peninsula [12].

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