Isolation and identification of Listeria monocytogenes from local cheese and evaluation of bacteria growth and proliferation in Hela cell culture

Abstract

Listeria monocytogenes is Gram-positive, spore-free and facultative anaerobic frequently transmitted to humans via water, meat and its products as well as raw vegetables. It is able to grow both intra and extra-cellular. The main way of bacteria transmission to human is through food material. The aim of this study is to isolate the bacteria from cheese using cold-enrichment and detection of it in Hela cell culture by light microscopy. Thus fresh local cheeses were sampled. Samples were moved to Trypton Soya Yeast Extract (TSYE) medium and were kept at 4°C for 1 to 3 weeks for enrichment. Then, they were cultured in Palcam and Listeria selective agar over given intervals. In order to detect colonies, first Gram staining and then biochemical tests were applied. Bacteria were inoculated in flasks containing Hella cell so as to detect bacteria entrance to the cell. Afterward, this cell culture medium was sampled on lam regularly. Samples were stained with Giemsa and then they were examined using light microscope. This investigation indicated that isolation of L. monocytogenes from diaries is possible using cold-enrichment without need for inhibitors antibiotics. In addition, it was found that this bacterium is able to enter into the dell and grow and proliferate in laboratory conditions. It lyses host cell after 48 h. The results of this study imply that L. monocytogenes exist in some contaminated local cheese. It also was found that it is able to grow and proliferate in cellular culture mediums and in laboratory conditions. Regarding the fact that the bacteria are omnipresent, more control over food material production and distribution cycle is needed so that it is prevented. Key words: Listeria monocytogenes, cheese, intracellular bacteria, Hela cell cultures