Isolation of [i]Listeria monocytogenes[/i] from milks used for Iranian traditional cheese in Lighvan cheese factories

Abstract

Traditional Lighvan cheese is a semi-hard cheese which has a popular market in Iran and neighboring countries. The aim of this study was evaluating the contamination of milks used for Lighvan cheese making with[i] Listeria monocytogenes[/i]. Raw milk samples were randomly collected from different cheese producing factories (sampling carried out from large milk tanks used cheese making in factories). Isolation of [i]L. monocytogenes[/i] was performed according to ISO 11290 and biochemical tests were done to identify and confirm L. monocytogenes. 9 samples (50%) of the 18 collected samples from milk tanks in Lighvan cheese producing factories were contaminated with [i]L. monocytogenes[/i]. The concentration of [i]L. monocytogenes[/i] in all 9 positive samples was 40 CFU/ml. This study is the first report of [i]L. monocytogenes[/i] contamination in raw milks used for Lighvan cheese production in Iran. Regarding the fact that these cheeses are produced from raw milk and no heating process is performed on them its milk contamination can be a potential risk for consumers