Source Tracking of Salmonella enterica in Broiler Production

Introduction: Salmonella is one of the major causes of foodborne disease throughout the world. Among foods of animal origin, poultry is among the most common sources of Salmonella. To effectively control the contamination of Salmonella in poultry, sources of the contamination should be identified throughout the production process.  Possible source of contamination can be identified by assessing clonal relationship between the suspected sources and the product of interest. Pulsed-Field Gel Electrophoresis (PFGE) was used to assess the genetic clonality of Salmonella isolates in this study.

Purpose:  To determine the main sources of Salmonella introduction to broiler during production in farm level by PFGE.

Methods:  Samples were collected chronologically from broiler and broiler farm environment throughout production period (6-weeks) from the same house, two times (2 flocks). Salmonella were isolated according to ISO 6579 method and serotyped according to the Kauffmann-White scheme. The serotypes common to both broiler and environment were selected and their clonal relationships were identified by PFGE according to the PulseNet standard protocol.

Results:  In the first flock, we found three Salmonella serotypes common to both broiler and farm environment, i.e., S. Derby, S. Albany, and S. Weltevreden. The sources of these serotypes were broiler house, feed, water, and house lizards. Indistinguishable PFGE patterns were obtained from all S. Derby isolates from feed, water and cloacal swab; S. Albany isolates from farm equipments, water, and broiler samples; and S. Weltevreden isolates from house lizards and broiler samples. In the second flock, we found one serotype, S. Albany, that was common to the catching boxes before used and live broiler at slaughterhouse. However, the PFGE analysis revealed that those isolates were unrelated. Interestingly, we also found Salmonella isolates of the same serotype with indistinguishable PFGE patterns in house lizards from different flocks that were collected at different time, indicating that this pest may play a significant role as a continuous reservoir for the Salmonella in the broiler farm. 

Significance: The study emphasized importance of effective cleaning and disinfecting farm environment, feed quality control, and pest management, especially house lizard, in controlling Salmonella in broiler.