Advanced Identification and Characterization of Listeria Species in Egyptian Local Soft Cheese

Abstract

Aims: one of the most important foodborne microorganisms is the Gram’s positive environmental wide spread Listeria spp. As the Listeria may be considered a public health concern so there is in needing to rapid, precise and reliable diagnosis of the organism in consumed food. The present study aimed to survey the presence of Listeria spp. among two popular consuming Egyptian white soft cheese using advanced biochemical, antibiotic susceptibility and molecular techniques. Methodology: Listeria spp. was investigated in 155 samples of two white soft cheeses (70 kareish cheese and 85 Damietta cheese) collected from street vendors and retail markets in Giza. The existence of Listeria spp. was tested through cultural and the identification was confirmed biochemically by Vitek2 compact system as well as molecular identification via diplex real time PCR using species specific primers. Results: The results of the study revealed the isolation of two Listeria spp. in a total number of 22 from155 samples (14.19%); 14 isolate out of 70 (20%) Kareish cheese while 8 isolates out of 85 (9.4%) Damietta cheese's samples. The 22 Listeria spp. isolates were differentiated into L. innocua 15 (68.18%), and L. monocytogenes 7 (31.81%) also their antimicrobial susceptibility was declared using advanced Vitek-2 compact system. The two Listeria spp. isolates were definitely confirmed by using diplex DNA hybridization real PCR technique. Conclusion: Soft raw milk based cheese is a popular food in Egypt and looked on as a risk for foodborne bacteria contamination. The data of this study pointed out that there is a potential risk of infection with Listeria, especially the public health concern L. monocytogenes. The current study presented Vitek-2 compact system as advanced technique for not only for identification and differentiation of Listeria strains but also for their antimicrobial susceptibility. Furthermore the using of diplex real PCR technique gives a chance for quick and precise identification.