A molecular based method for rapid detection of Salmonella spp. in poultry dust samples

Abstract

Salmonellosis, caused by Salmonella spp., is a widely reported foodborne zoonosis frequently associated with ingestion of poultry products. Salmonella vaccination of chickens can be used to reduce bacterial shedding and risk of human infection. To determine Salmonella burden in chicken farms, culture methods of environmental samples that require a turn-around time of 5-7 days are usually used. Rapid screening using molecular assays such as PCR of pre-enriched broth has been reported for Salmonella spp. detection in feed, floor dust, and drag swabs within 2-3 days. Here we report an adaptation of the method for detection of Salmonella in poultry dust samples collected using a settle plate method under experimental conditions. Key features:•Passive dust sample collection using dry settle plates without media suspended from dropper lines of drinkers.•Small amount of sample required for the pre-enrichment process.•Quantification of Salmonella DNA with high sensitivity using an inexpensive extraction protocol.

Keywords: Chicken; Disease monitoring; Poultry dust; Salmonella; qPCR.

Graphical abstract

Fig 1

Buffered peptone water broth media after incubation of 100 mg of dust samples in 10 ml of BPW at 37 °C for 18 h. Dust formed a sediment at the bottom of the broth culture tubes and turbidity was observed mostly in the middle of the tube. The arrow mark indicates the pipetting site for transfer of the pre-enriched sample for DNA extraction.

Fig. 2

Salmonella load in dust samples enriched or not by incubation in BPW with DNA extraction by a commercial kit or a simple sample boiling method. Dust samples were collected at the indicated time points from experimental flock challenged with a field isolate of S. Typhimurium DT 135 using a seeder bird technique at 1 day of age and vaccinated with a non-propagative strain of live Salmonella vaccine at 10 and 16 weeks of age.

Fig. 3

A. Intraclass correlation coefficient of Log₁₀Salmonella CFU/g of BPW enriched dust extracted by Kit and boiling method. Here, the intraclass correlation coefficient (ICC) = 0.99, degrees of freedom (df) = 39 and P < 0.0001.B. intraclass correlation coefficient of Log₁₀Salmonella CFU/g of non-enriched dust extracted by kit and BPW enriched dust extracted by kit. Here, the ICC value is 0.72, degrees of freedom (df) = 39 and P < 0.0001.