مقالات پذیرفته شده در سومین کنگره بین المللی زیست پزشکی
Detection of Salmonella species in crude and cooked meats of chickens, sheep and cattle and eggs , phenotypically, serologically and genetically
Detection of Salmonella species in crude and cooked meats of chickens, sheep and cattle and eggs , phenotypically, serologically and genetically
Sanaz Mashhadi,1Roozbeh Yalfani,2,*Marzye Pazoki,3
1. Department of Microbiology, Faculty of Biology Science, Islamic Azad University,Varamin-Pishva branch, Tehran, Iran 2. Department of Nursing, School of Medicine, Islamic Azad University,Varamin-Pishva branch, Tehran, Iran 3. Department of Microbiology, Faculty of Biology Science, Islamic Azad University,Varamin-Pishva branch, Tehran, Iran
Introduction: Salmonella infections are worldwide and constitute an important public health problem in many parts of the world. There are several transmission routes for salmonellosis, but the majority of human infections are derived from the consumption of contaminated foods especially those of animal origin. A variety of food products, especially poultry and other types of meat products including minced meats, are the most important sources of human Salmonella infection.
Most serotypes of S. enterica cause self-limiting gastroenteritis characterized by diarrhoea, abdominal cramps and sometimes vomiting and fever. Two serotypes, S. typhi and S. paratyphi, causes systemic fevers that can be fatal without therapy.
The detection and identification of Salmonella spp. is time consuming to the food industry. To detect Salmonellae more rapidly, an alternative method to the conventional culture method was evaluated using polymerase chain reaction (PCR). PCR has been demonstrated to be a very specific and sensitive method for the detection of Salmonellae.
Several genes have been used to detect Salmonella in natural environmental samples as well as food and faecal samples. Virulence chromosomal genes including; invA, invE, himA phoP are target genes for PCR amplification of Salmonella species. The invA gene of Salmonella contains sequences unique to this genus and has been proved as a suitable PCR target, with potential diagnostic applications.
Therefore, this study was performed to identify Salmonella spp. contamination in cattle, sheep and poultry meats and eggs in 1396 in Tehran.
Methods: A total of 500 samples including 100 cattle, 100 sheep, 150 chicken meat and 150 egg samples were collected through random sampling in Tehran city. From each sample a quantity of 25g was taken using sterile tools. Microbiological detection of Salmonella was done by use of non-selective pre-enrichment broth (Buffered peptone water, 37°C, 18 h), Selective enrichment broth (Rappaport-Vassiliadis Medium with soya (RVS broth), 41.5°C, 24 h ), Selective Plating (Xylose Lysine Desoxychoclate agar X.L.D. 37°C, 24 hours). Biochemical confirmation tests were as follows: Triple- sugar iron agar (TSI agar), Urease production (Christensen medium with urea), Peptone medium with tryptophan (indole reaction), Medium with Lysine (Lysine decarboxylation medium), Clark media (Voges-Proskauer (VP) reaction), ONPG medium (Reagent for detection of β-galactosidase).
Then Isolates were subcultured on nutrient slope for 24 hours at 37ºC for application of slide agglutination technique, two homogenous suspensions were made on a slide by suspending a piece of suspected colony in a drop of sterile physiological saline. A drop of each of separate O and H Salmonella antisera were added separately to each of the suspensions with standard loop thoroughly mixed to bring the microorganisms in close contact with antisera.
For PCR, 48-h RV broth was used as sample material. After incubation, 1.5 ml of RV broth was transferred into an Eppendorf tube. The DNA was extracted following the standard methods described by articles. Salmonella specific primers, have respectively the following nucleotide sequence based on the invA gene of Salmonella 5´ GTG AAA TTA TCG CCA CGT TCG GGC AA - 3´and 5´ TCATCG CAC CGT CAAAGG AAC C -3´.
The amplified DNA products from PCR were analysed with electrophoresis on 1.2% agarose gels stained with ethidium bromide and visualized by UV illumination.
Results: In this study, out of 500 collected samples, 43 (8.6%) Salmonella isolates were collected, from which 19 isolates (44.2%) were identified as S. typhimurium, 13 isolates (30.2%) as S. enteritidis and 11 isolates (25.5%) as S. gallinarum.
The number of contaminated samples which Salmonella spp. was isolated, were as follows: 23 samples of chicken meats (53.4%), 8 samples of beef (18.6%), 7 samples of eggs (16.2%), and 5 samples of sheep (11.6%). All isolates carried invA gene.
Conclusion: The findings show that the rate of red and white meat contamination with Salmonella is high. They could be a potential vehicle for food-borne infections and implementation of preventive measures and consumer food safety education efforts are needed. Proper cooking of meat and chicken products before consumption and improving personal and meat hygiene in the line of meat production from farm and slaughterhouses to fork should be adopted to ensure the safety of meat and meat products for human consumption.