Salmonella is one of the most important bacterial pathogens responsible for many zoonotic food-related infectious diseases. Quantitative detection of the foodborne Salmonella contamination in various food sources is therefore critical for preventing the related disease outbreaks. In this study, we developed and evaluated a reliable real-time polymerase chain reaction (RT-PCR) assay to detect the Salmonella contamination quantitatively. The experimental results showed that our invA gene-specific quantitative RT-PCR (qRT-PCR) assay provides a strong correlation between the Cq values and the direct plate counts of Salmonella species in the artificially formulated samples. Further study may be necessary to identify more accurate correlation and equation that can apply to Salmonella spp.

Salmonella are widespread in humans and animals worldwide and are public health concern as causative pathogens of food poisoning. The aim of this study was to survey the level of Salmonella contamination in a chicken slaughter plant and to analyze the characterization of Salmonella isolates by serotype, antimicrobial resistance and phage type. Among 170 feces of transport box from 17 farms and 100 carcasses originated 20 farms, Salmonella were identified in 54 feces (13 farms) and 29 carcasses (11 farms). A total of 150 Salmonella isolates from feces and 73 isolates from carcasses were analyzed. One hundred and forty five isolates (96.7%) from feces and 68 isolates (93.2%) from carcasses were Salmonella enteritidis (S. Enteritidis) and 3 isolates and 2 isolates from feces were S. isangi and S. blockley, respectively. Three isolates from carcasses were S. blockley, and S. isangi was not detected at carcasses. The most common phage type (PT) of S. Enteritidis was PT 1, followed by PT 1c, PT 21, PT 24var, PT 6a, and PT 7. Antimicrobial resistance testing was performed by disk diffusion method using 19 antibiotics. The highest percentage of antimicrobial resistance of isolates from feces and carcasses were found to the following antibiotics: trimethoprim/sulfamethoxazole (Sxt, 83.3% and 93.2%), tetracycline (Te, 40.0% and 15.1%) and ampicillin (Am, 16.0% and 20.5%). Also, the most frequent multiresistance pattern of isolates from feces and carcasses were Te-Sxt (34.0%) and Am-Sxt (19.2%), respectively.