First Report of Listeria monocytogenes Serotypes Detected from Milk and Milk Products in Sri Lanka

Abstract

Listeria monocytogenes is the causative organism of listeriosis, which primarily affects immune-compromised individuals, including pregnant women. Contamination of milk and milk products with L. monocytogenes is a serious problem to the world and to the developing countries like Sri Lanka. Even the presence of low numbers of L. monocytogenes is a potential risk since this organism is capable of multiplying at ambient and under refrigerated conditions. The main aim of the study is to detect the circulating serotypes in dairy industries using molecular methods and primarily to trace the lineage of these serotypes with a focus on food safety and disease prevention. Altogether total of 266 samples from raw milk, pasteurized milk, ice cream, curd, yogurt and cheese were collected from many parts of the country, tested for the presence of L. monocytogenes and studied the serotype. L. monocytogenes was detected in all types of the above-mentioned milk and milk products. Out of total L. monocytogenes strains detected by PCR, 61.51%, 11.53% and 4% belong to serotypes 1/2a (or 3a) [lineage II], 1/2b (or 3b) [lineage I] and, 1/2c (or 3c) [lineage II] respectively. It has been observed previously that serotypes (1/2a), (1/2b) isolated from raw milk samples been linked to multiple human listeriosis outbreaks. This study revealed the serotypes of L. monocytogenes circulating in Sri Lanka, thus makes an alarm to the health authorities to be more vigilant about the probable outbreaks of listeriosis in Sri Lanka. This is the first report on circulating L. monocytogenes serotypes in Sri Lanka.