Microbial survey of ready-to-eat salad ingredients sold at retail reveals the occurrence and the persistence of Listeria monocytogenes Sequence Types 2 and 87 in pre-packed smoked salmon

BMC Microbiology

Research Article

Pei Sze Valarie Lee¹  Hyun-Gyun Yuk¹  Man Ling Chau²  Joanne Su Lin Kang²  Ramona Alikiiteaga Gutiérrez²  Hapuarachchige Chanditha Hapuarachchi²  Kyaw Thu Aung²  Youming Ng²  Hooi Ming Yap²  Lee Ching Ng³  Pei Ying Lim⁴ 

[1] Department of Chemistry, Food Science and Technology Programme, National University of Singapore, 3 Science Drive 3, 117543, Singapore, Singapore;Environmental Health Institute, National Environment Agency, 11 Biopolis Way, #04-03/04, Helios Block, 138667, Singapore, Singapore;Environmental Health Institute, National Environment Agency, 11 Biopolis Way, #04-03/04, Helios Block, 138667, Singapore, Singapore;School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore, Singapore;School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore, Singapore;

关键词: Microbial safety and quality;    Salads;    Smoked salmon;    Listeria monocytogenes;    Multi Locus Sequence Typing (MLST);    Food safety;   

DOI  :  10.1186/s12866-017-0956-z

 received in 2016-06-28, accepted in 2017-02-14,  发布年份 2017

来源: Springer

【 摘 要 】

BackgroundAs the preparation of salads involves extensive handling and the use of uncooked ingredients, they are particularly vulnerable to microbial contamination. This study aimed to determine the microbial safety and quality of pre-packed salads and salad bar ingredients sold in Singapore, so as to identify public health risks that could arise from consuming salads and to determine areas for improvement in the management of food safety.ResultsThe most frequently encountered organism in pre-packed salad samples was B. cereus, particularly in pasta salads (33.3%, 10/30). The most commonly detected organism in salad bar ingredients was L. monocytogenes, in particular seafood ingredients (44.1%, 15/34), largely due to contaminated smoked salmon. Further investigation showed that 21.6% (37/171) of the pre-packed smoked salmon sold in supermarkets contained L. monocytogenes. Significantly higher prevalence of L. monocytogenes and higher Standard Plate Count were detected in smoked salmon at salad bars compared to pre-packed smoked salmon in supermarkets, which suggested multiplication of the organism as the products move down the supply chain. Further molecular analysis revealed that L. monocytogenes Sequence Type (ST) 2 and ST87 were present in a particular brand of pre-packed salmon products over a 4-year period, implying a potential persistent contamination problem at the manufacturing level.ConclusionsOur findings highlighted a need to improve manufacturing and retail hygiene processes as well as to educate vulnerable populations to avoid consuming food prone to L. monocytogenes contamination.

【 授权许可】

CC BY   
© The Author(s). 2017