Salmonella spp. transmission in a vertically integrated poultry operation: Clustering and diversity analysis using phenotyping (serotyping, phage typing) and genotyping (MLVA).

Helen Kathleen Crabb,Joanne Lee Allen,Joanne Maree Devlin,James Rudkin Gilkerson,Colin Reginald Wilks,Simon Matthew Firestone,Anderson De Souza Sant’Ana

doi:10.1371/journal.pone.0201031

Abstract

The transmission of Salmonella enterica within a vertically integrated poultry operation was investigated longitudinally over an 18-month period (2013–2014). Thirty six percent of all samples collected (1503 of 4219) were positive for salmonellae with seven Salmonella enterica subsp. enterica serovars, and one Salmonella enterica subsp. salamae serovar detected. Both Salmonella enterica subsp. enterica serovars Infantis and Typhimurium were detected in all locations sampled. Salmonella Typhimurium was the most frequently detected serovar (63% of serotyped samples) with 8 phage types (PT) and 41 multiple-locus variable-number tandem-repeats analysis (MLVA) profiles identified. The most frequently identified phage types were PT135a and DT135. A total of 62 PT/MLVA combinations were observed. MLVA profiles 03-14-10-09-525 and 03-15-11-11-525 were the most frequently identified and 83% of the isolates shared at least one MLVA profile with an isolate from another phage type. The use of phage typing and MLVA profiling, on their own or in combination, were insufficient to understand the complexity of the epidemiological relationships between locations within this production system. Despite the high level of apparent diversity, cluster analysis was unable to differentiate the transmission pathways of all S. Typhimurium variants detected within the integrated enterprise. Using additional epidemiological information, the parent breeder rearing site was identified as the most likely point of introduction of two S. Typhimurium isolates into the production system with subsequent dissemination to the broiler flocks via the hatchery. This complexity is unable to be resolved in the absence of intensive sampling programs at all generations of the production system.

Highlights

The epidemiology of Salmonella enterica transmission within a vertically integrated chicken meat operation is poorly described
There are a small number of studies that characterize S. enterica isolates beyond serovar identification across entire poultry meat production systems but none have been conducted in Australia [11,12,13,14]
Thirty six percent (1503/4219) of the samples collected were positive for Salmonella enterica subsp. (Table 1)

Summary

Introduction

The epidemiology of Salmonella enterica transmission within a vertically integrated chicken meat operation is poorly described. Three Australian publications from the 1970s describe the dissemination of S. enterica serovars within integrated broiler operations [8,9,10]. These studies were a descriptive analysis of the occurrence of S. enterica at each component of the production system and implicated feed as the common source of introduction. There are a small number of studies that characterize S. enterica isolates beyond serovar identification across entire poultry meat production systems but none have been conducted in Australia [11,12,13,14]. Enteritidis do occur in Australia but are most frequently associated with overseas travel [16] This offers a novel opportunity to understand Salmonella enterica subsp.

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