Source tracking of Salmonella enterica in broiler production by Pulsed-Field Gel Electrophoresis (PFGE)

Abstract

The objectives of this study were to determine the chronological dissemination and the main sources of Salmonella introduction to broiler production throughout rearing period by Pulsed-Field Gel Electrophoresis (PFGE). The samples were collected from a commercial broiler farm up to 3 cycle productions from a commercial broiler farm in Northeastern part of Thailand during 2010-2012. The samples were collected from the same broiler house and the total number of samples from broiler and environment were 1,350 and 697, respectively. The isolates with common Salmonella serotypes between broiler and environment were chosen for source tracking by subtyping with PFGE. The result from the first flock showed that contaminated water and new feed were possibly the primary sources of Salmonella to the broiler flock because of the identical PFGE pattern of S. Albany (subtype ABa1) and S. Derby (subtype Da1) among feed, water and broiler. The contaminated water was also possibly the source of Salmonella contamination to broiler house and equipment because S. Albany PFGE subtype ABa1 was found from both water and broiler house equipment after disinfection. Salmonella isolates were not detected from broiler in the second flock. However, the same PFGE subtypes of S. weltevreden (subtype Wa1, Wa2) from house lizards and environment between the first and the second flock were found. The result indicated that house lizards may act as a reservoir between flocks. In the third flock, S. Corvallis (PFGE subtype Ca1) was found from the day old chick. This PFGE subtype was also found throughout the rearing period from broiler and also from pest and environment in the broiler house. So, the contaminated day old chick was the main source of Salmonella contamination in this flock. In conclusion, this study suggested that contaminated water and feed including infected day old chick were among the main sources of Salmonella contamination in broiler farm. In addition, the contamination of house and equipment, litter, transportation equipment and pest should also be concerned as a possible source of Salmonella contamination in broiler flock.