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Limited Emergence of Salmonella enterica Serovar Infantis Variants with Reduced Phage Susceptibility in PhagoVet-Treated Broilers
by
, , , , and
Sandra Sevilla-Navarro
1,†,
Jennifer Otero
2,†,
Júlia López-Pérez
2,
Jan Torres-Boncompte
1,
Tiago Prucha
3, 
Maarten De Gussem
3,
Daniela Silva
4,
Julia Burgan
4,
Pablo Catalá-Gregori
1,
Pilar Cortés
2,* and
Montserrat Llagostera
2 1
Centro de Calidad Avícola y Alimentación Animal de la Comunidad Valenciana (CECAV), 12539 Alquerias NP, Castellón, Spain
2
Molecular Microbiology Group, Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Spain
3
VETWORKS BVBA, Knokstraat 38, 9880 Poeke, Belgium
4
ALS Life Sciences Portugal, Zona Industrial de Tondela ZIM II lote 6, 3460-070 Tondela, Portugal
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Animals 2024, 14(16), 2352; https://doi.org/10.3390/ani14162352
Submission received: 18 July 2024
/
Revised: 9 August 2024
/
Accepted: 12 August 2024
/
Published: 14 August 2024
(This article belongs to the Special Issue Salmonella and Salmonellosis: Implications in Public Health)
Simple Summary
Simple Summary: One of the main concerns associated with phage applications is the potential emergence of bacterial variants exhibiting reduced susceptibility to bacteriophages, which may jeopardize the success of such applications, as occurs with antibiotics. In this work, we studied the emergence of reduced-phage-susceptibility variants in broiler trials challenged with Salmonella enterica serovar Infantis and treated with the PhagoVet product. We characterized the bacteriophages composing the PhagoVet product at both a microscopic and genomic level, which displayed a broad host range of infection against 271 strains representing 18 Salmonella serovars. Our results indicate that the emergence of reduced-phage-susceptibility variants is unlikely to compromise the efficacy of oral PhagoVet against S. Infantis.
Abstract
Salmonella enterica serovar Infantis (S. Infantis) poses a growing issue in the poultry sector, with phage-based products emerging as a safe and effective control measure. This study investigated the emergence of reduced-phage-susceptibility variants (RPSV) of S. Infantis in PhagoVet-treated broilers, given that RPSV could undermine phage treatment efficacy. The bacteriophages in the PhagoVet product were characterized using transmission electron microscopy (TEM), genome sequencing, and infection profiling. Furthermore, two broiler trials were conducted: a challenge group (T1) and a challenge-and-treated group (T2). The S. Infantis infective dose was set at 104 and 106 colony-forming units (CFUs) per animal, with PhagoVet administration at 106 and 108 plaque-forming units (PFUs) per animal, in Trials 1 and 2, respectively. The results revealed that the four PhagoVet bacteriophages belonged to different genera. PhagoVet evidenced broad-spectrum efficacy against 271 strains representing 18 Salmonella serovars. In Trial 1, PhagoVet reduced bacterial counts in feces to nearly undetectable levels by day 42, with no RPSV detected. However, in Trial 2, three and five RPSVs were detected in feces and ceca, respectively. Consequently, PhagoVet demonstrated efficacy against S. Infantis in broilers, and the potential impact of RPSV is deemed unlikely to compromise its efficacy.
