Abstract
BackgroundReady-to-eat (RTE) vegetables have become increasingly popular along with the trend of moving towards a healthy lifestyle. However, RTE vegetables are at a higher risk of containing pathogens, maybe owing to lack of rigorous sanitization procedures. To understand the prevalence and potential risk of Listeria monocytogenes in RTE vegetables, we investigated the contamination level and characteristics of L. monocytogenes isolated from fresh vegetables.ResultsTwenty-three (5.49%) of the 419 vegetables samples were positive for L. monocytogenes. Phylogenetic group I.1 (1/2a-3a) and II.2 (1/2b-3b-7) strains were predominant in 30 isolates, which accounted for 33.3 and 50.0%, respectively. Multilocus sequence typing of the 30 isolates grouped them into nine sequence types (STs). The most common STs were ST87 (36.7%) and ST8 (26.7%). Virulence analysis showed that all 30 isolates harbored eight classical virulence genes, 10.0% isolates harbored the llsX gene (ST3 and ST1 strains), and 36.7% carried the ptsA gene and belonged to ST87. Approximately 83.3% isolates carried full-length inlA, whereas five isolates had premature stop codons in inlA, three of which belonged to ST9 and two to ST8. Antibiotic susceptibility showed the isolates were varyingly resistant to 13 antibiotics, 26.7% of the isolates were multi-drug resistant.ConclusionsThe fresh vegetables contain some potential hypervirulent L. monocytogenes (ST1 and ST87) in the Chinese markets. In addition, the high rate of L. monocytogenes isolates was multi-drug resistant. Fresh raw vegetables may be a possible transmission route for L. monocytogenes infection in consumers. Therefore, sanitization of raw fresh vegetables should be strengthened to ensure their microbiological safety when used as RTE vegetables.
Highlights
Ready-to-eat (RTE) vegetables have become increasingly popular along with the trend of moving towards a healthy lifestyle
Phylogenetic group analysis Multiple PCR was used to analyze the phylogenetic group of 30 isolates obtained from 23 L. monocytogenes-positive samples (Additional file 1: Figure S1)
L. monocytogenes of two different phylogenetic groups were isolated from three lettuce samples, one cucumber sample and one coriander sample, suggesting that there were different serotypes of L. monocytogenes contaminating the same vegetable sample
Summary
Ready-to-eat (RTE) vegetables have become increasingly popular along with the trend of moving towards a healthy lifestyle. Listeria monocytogenes is a common Gram-positive facultative anaerobic bacillus that is recognized as one of four foodborne pathogens by the World Health Organization. It can invasively infect humans and animals, causing severe listeriosis leading to meningoencephalitis, sepsis and fetal infection or miscarriage in pregnant women, with a mortality rate of 20–30% [3]. A study revealed that L. monocytogenes was detected in 6.67% fruit and vegetable products from 2011 to 2015 in Jilin Province, China (Yang et al, 2017) Both in Europe and USA, a link between foodborne disease outbreaks and pathogen (such as L. monocytogenes) contaminated green leafy vegetables, such as lettuce and spinach, and their RTE salads has been reported [4]. China is the largest vegetable producer and consumer in the world, with an output volume of vegetables and processed products of 10.1 million tons in 2015 [9], there is no uniform method for risk assessment and management of L. monocytogenes in RTE vegetables [10],which are mostly consumed raw or after minimal processing and pathogen contamination poses a health risk
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
