Optimization of Cell Permeabilization for Rapid Detection of Salmonella in Pork by FISH

Abstract

Salmonella spp. are one of the major causes of infectious gastroenteritis. The route of infection is usually ingestion of contaminated food. Due to the severity of the disease, it is worthwhile to identify appropriate preventive measures. Bacterial culture method is the gold standard method, but it is time-consuming (at least 4-6 days). Therefore, in this research, the fluorescence in situ hybridization technique (FISH) was optimized for rapid and accurate detection of Salmonella spp. in contaminated pork using a 3¢-end tailing oligonucleotide probe. The optimum digestion condition for cell permeation with lysozyme was 1 mg/ml at 37^oC for 3 min. The lowest concentration of Salmonella detected in spiked-pork samples without a pre-enrichment step was 10⁷ cfu/ml. Using the FISH method, 30 out of 35 market pork samples were positive, compared to 29 out of 35 positive results produced by the culture method. FISH gave 3 false positive and 2 false negative results. According to Kappa Statistics, agreement between the standard culture method and the fluorescence in situ hybridization technique was 0.46, which can be accepted as being in the moderate range of standard value. Thus, FISH should be considered as an important rapid screening tool for detection of Salmonella spp. contamination.