Application of the lytic bacteriophage Rostam to control Salmonella enteritidis in eggs.

Foodborne Salmonella enteritidis infections place human health at risk, driven by regular outbreaks and individual cases by different contaminated food materials. This study was conducted to characterize and employ a single bacteriophage as a potential biocontrol agent. Phage Rostam was isolated, characterized and then applied as biocontrol agent against S. enteritidis in liquid whole eggs and eggshell. Rostam is a novel myovirus belonging to the Rosemountvirus genus and active against Escherichia coli and Salmonella spp. Rostam is stable in a pH range from 4 to 10, a salt concentration of 1-9 %, whereas UV radiation gradually reduces phage stability, and its 53 kb genome sequence indicates this phage does not contain known toxins or lysogeny-associated genes. Its latent period is short with a burst size of 151 PFU/cell, under standard growth conditions. Killing curves indicate that at higher multiplicities of infection (MOI), the reduction in S. enteritidis count is more pronounced. Phage Rostam (MOI 10,000) reduces S. enteritidis growth to below the detection limit at 4 °C in both liquid whole eggs and on the eggshell within 24 h. Due to its high lytic activity and stability in relevant conditions, Rostam has the potential to be an efficient biopreservative for egg and egg products.

The morphological and biological characteristics of a virulent PI phage isolated from slaughterhouse sewage in Shiraz, Iran.

BACKGROUND AND OBJECTIVES: Foodborne pathogens are among the serious problems all around the world and thus a novel and natural strategy to control and to inhibit such pathogens is highly demanded nowadays. The aim of this study was to isolate a specific bacteriophage of Escherichia coli O157:H7 from sewage in Fars province, Iran to determine its morphological and antimicrobial activities. MATERIALS AND METHODS: In order to isolate the bacteriophage of E. coli O157:H7, 10 samples of slaughterhouse wastewaters were used. Double-Layer Agar method was employed to isolate the bacteriophage. To identify the fine structure of the bacteriophage, electron microscope was employed. Host range and antibacterial activity of the phage was also investigated, in vitro. RESULTS: The morphological and biological characteristics of a virulent Siphoviridae phage, PI, are reported. It was found that infection of E. coli O157:H7 strains with this specific bacteriophage produce clear plaques. In the one-step growth analysis, it was confirmed that the phage has been characterized with a very short rise period (around 15 min), an average burst size of 193 PFU/cell, high infectivity and potent lytic action. The bacteriolytic activity of PI was also investigated, in vitro. It was also clarified that at the MOI of 100, 10 and 1, the phage rapidly lysed the bacterial cells within 0.5 or 2 h. CONCLUSION: These results indicate that the phage PI is a newly discovered phage against E. coli O157:H7 in Iran which may be recommended to use as bio-control purposes.

The role of Linguatula serrata nymph in transmission of enteric bacterial pathogens to internal organs in sheep.

Linguatula serrata is a worldwide zoonotic parasite belong to phylum Athropoda. When the eggs are swallowed by intermediate host, the larvae are released in intestine and reach the mesenteric lymph nodes (MLNs) and occasionally liver, lungs, heart, kidneys, spleen, and other body organs by the blood and lymph circulation. There are a few evidences showing transmission of microorganisms by migrating L. serrata. The aim of this study was to determine the role of L. serrata nymph in transmission of enteric bacterial pathogens to internal organs of sheep. For this purpose 11 parasite positive and 11 parasite negative MLNs to L. serrata were obtained from the native slaughtered sheep and were examined microbiologically in terms of bacterial contamination. The average total bacterial count and Escherichia coli count in the parasite positive samples were respectively 6.7 and 3.3 times higher than parasite negative ones (P < 0.05). However no significant differences were found for Salmonella and intestinal enterococci between parasite positive/negative samples. This indicates that L. serrata nymphs play as vehicles for bacteria and so contaminate offal. L. serrata nymphs transfer some bacterial agents to internal organs and enhance post mortem spoilage of the infected organs. It is also able to transfer some bacterial pathogens to internal organs which could potentially be the etiology of severe infectious or even zoonotic diseases. Especially in some regions where the consumption of raw or semi-cooked lymph nodes and other visceral organs are common.

Comparison of Three Different DNA Extraction Methods for Linguatula serrata as a Food Born Pathogen.

BACKGROUND: One of the most important items in molecular characterization of food-borne pathogens is high quality genomic DNA. In this study, we investigated three protocols and compared their simplicity, duration and costs for extracting genomic DNA from Linguatula serrata. METHODS: The larvae were collected from the sheep's visceral organs from the Yazd Slaughterhouse during May 2013. DNA extraction was done in three different methods, including commercial DNA extraction kit, Phenol Chloroform Isoamylalcohol (PCI), and salting out. Extracted DNA in each method was assessed for quantity and quality using spectrophotometery and agarose gel electrophoresis, respectively. RESULTS: The less duration was regarding to commercial DNA extraction kit and then salting out protocol. The cost benefit one was salting out and then PCI method. The best quantity was regarding to PCI with 72.20±29.20 ng/µl, and purity of OD260/OD280 in 1.76±0.947. Agarose gel electrophoresis for assessing the quality found all the same. CONCLUSION: Salting out is introduced as the best method for DNA extraction from L. seratta as a food-borne pathogen with the least costand appropriate purity. Although, the best purity was regarding to PCI but PCI is not safe as salting out. In addition, the duration of salting out was less than PCI. The least duration was seen in commercial DNA extraction kit, but it is expensive and therefore is not recommended for developing countries where consumption of offal is common.