Polyphasic characterization of Salmonella Enteritidis isolates on persistently contaminated layer farms during the implementation of a national control program with obligatory vaccination: A longitudinal study

Abstract

Since 2007, a national Salmonella control program including obligatory vaccination has been ongoing in Belgium. In this context, the aim of the present study was to investigate the diversity of Salmonella enterica serovar Enteritidis isolates on 5 persistently contaminated Belgian layer farms and to examine the potential sources and transmission routes of Salmonella Enteritidis contamination on the farms during successive laying rounds. A collection of 346 Salmonella isolates originating from the sampled farms were characterized using a combination of multilocus variable number of tandem repeat analysis (MLVA) and phage typing (PT). On each farm, one or 2 dominant MLVA-PT types were found during successive laying cycles. The dominant MLVA type was different for each of the individual farms, but some farms shared the same dominant phage type. Isolates recovered from hens' feces and ceca, egg contents, eggshells, vermin (mice, rats, red mites, and flies), and pets (dog and cat feces) had the same MLVA-PT type also found in the inside henhouse environment of the respective layer farm. Persistent types were identified in the layer farm inside environment (henhouse and egg collecting area). Furthermore, this study demonstrated cross-contamination of Salmonella between henhouses and between the henhouse and the egg collecting area. Additional isolates with a different MLVA-PT type were also recovered, mainly from the egg collecting area. A potential risk for cross-contamination of Salmonella between the individual layer farms and their egg trader was identified.

Application of Molecular Approaches for Understanding Foodborne Salmonella Establishment in Poultry Production

“…Strategies have been explored in attempts to either prevent establishment of Salmonella in laying hens at various stages of the production cycle or eliminate already established Salmonella. Attempts have been made to protect birds against Salmonella using a variety of live and attenuated vaccines that were specifically designed to limit Salmonella colonization and infection in young birds via resistance immunologically [231][232][233]. As more emphasis is being placed on preharvest prevention of Salmonella colonization there will be further need to develop and expand preventative interventions such as vaccines.…”

<i>Salmonella</i> Contamination in Layer Farms in China: Detection and Genetic Analysis

“…Previous studies have shown that the transfer process of eggs presents a potential risk for cross-contamination (Davies and Wray, 1994). Based on multilocus variable number of tandem repeat analysis-phage typing, Dewaele et al (2012a) also suggested that cross-contamination may occur between the henhouse and egg collection areas.…”

Phage and MLVA Typing of Salmonella Enteritidis Isolated from Layers and Humans in Belgium from 2000–2010, A Period in which Vaccination of Laying Hens was Introduced

“…Enteritidis isolates on five persistently S . Enteritidis contaminated Belgian layer farms in the period 2008–2011, PT4b and PT6c were predominantly isolated (Dewaele et al., ).…”

“…Enteritidis isolates and the diversity of isolates before and after the implementation of the NCP. Therefore, phage typing (PT) (NRCSS, ) and Multiple‐locus variable number tandem‐repeat assay (MLVA) typing (Beranek et al., ; Dewaele et al., ) of available layer farm related S . Enteritidis isolates from 2000 to 2010 were compared with strains isolated from humans from 2002 to 2010 and both sets were collected in Belgium.…”