Abstract
Listeria monocytogenes is a ubiquitous Gram positive organism causative agent of many hazardous conditions like meningitis and sepsis. To isolate L. monocytogenes from various food samples collected from different markets in Iran and evaluate pathogenic potential of the isolates by determining two virulence associated genes (hly and plc-A) and sequencing them, a total of 130 samples including dairy and meat products were collected. Cold enrichment method was used for the isolation of Listeria monocytogenes. The isolated pathogens were identified and confirmed by biochemical and polymerase chain reaction (PCR). PCR method was done to amplify two gene fragments, a 1590 and 954 bp for hly and plc-A genes, respectively by using sequencing primers. Listeria monocytogenes was isolated from 3.1% of all samples. The bacterium was isolated 2.5% in dairy and 4% in meat samples. All isolates were hemolytic and positive for hly gene. Also 100% of isolates had plc-A gene. The results of this study indicates that consumption of ready to eat food is hazardous specially for high risk persons .Besides that, pathogenic potential of isolated strains is important because of existences of virulence gene in all of the isolates. Key words: Listeria monocytogenes, hly and plc-A genes, polymerase chain reaction (PCR), dairy, meat.
Highlights
Listeria monocytogenes is an opportunistic intracellular pathogen that has become an important cause of human food borne infections worldwide (Liu, 2006)
To isolate L. monocytogenes from various food samples collected from different markets in Iran and evaluate pathogenic potential of the isolates by determining two virulence associated genes and sequencing them, a total of 130 samples including dairy and meat products were collected
L. monocytogenes was isolated from four tested samples
Summary
Listeria monocytogenes is an opportunistic intracellular pathogen that has become an important cause of human food borne infections worldwide (Liu, 2006). In recent years different epidemiological and experimental investigations revealed that contaminated food is an important route for transmission of bacteria to humans. It has been shown that the main source of infections is ready-to-eat (RTE) foods with long shelf - life making L. monocytogenes one of the major causative agents of food-related deaths (O’Connor et al, 2010). Listeria species are able to survive many food manufacturing processes and with a recent increased consumption of RTE and heat to eat products, L. monocytogenes has emerged as a significant food borne pathogen, causing serious illness in infants, pregnant women, elderly and immunocompromised individuals (Liu et al, 2007; Lotfollahi et al, 2011).
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