Microbial and Pathogenic Contamination of Ready-to-eat Fresh Vegetables in Korea

Abstract

The purpose of this study was to evaluate microbiological contamination of fresh vegetables in Korea. Twenty types of vegetables were tested for total aerobic bacteria, coliforms, Escherichia coli, yeast and mold, and pathogenic bacteria such as Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, Salmonella, E. coli O157:H7, Cronobacter sakazakii, Shigella, and Campylobacter. Levels of total aerobic bacteria and coliform on 20 vegetables were between 3.74 and 8.04 log CFU/g, and 0.16 and 5.02 log CFU/g, respectively. The highest contamination levels of total aerobic bacteria were observed on water dropwort, sprouts, mungbean sprout, and ballflower root. There was no significant difference (p>0.05) in microbial contamination levels of total aerobic count, coliform, E. coli, yeast and mold between organic and nonorganic vegetables. When isolation methods using selective agars were applied, L. monocytogenes, B. cereus, Salmonella and Campylobacter were isolated from some fresh vegetable samples. Results of API kit tests showed that L. monocytogenes was identified on Chinese cabbage, cucumber, soybean sprouts, and iceberg lettuce while Salmonella was identified on Korean leek. Furthermore, Campylobacter jejuni was also identified in more than 50 of the 100 samples. However, when positive samples from API kit were tested for real-time PCR or 16S rRNA sequencing method, only B. cereus from perilla leaf, carrot, water dropwort, and sprouts showed positive results. These results indicate that selective agar and API kit detection methods might result in false positive results for some pathogens. Therefore, studies need to improve isolation or confirmation methods for such pathogens.

Predictive Models for the Growth Kinetics of Listeria monocytogenes on White Cabbage

“…() reported that about 9.4 million cases of foodborne illness caused by 31 major pathogens; among which, there are about 1,591 cases of foodborne illness annually caused by L. monocytogenes , resulting in 1,455 hospitalizations and 255 deaths in the U.S.A. Several listeriosis outbreaks associated to the consumption of raw vegetables including raw celery, tomatoes, lettuce, cabbage and coleslaw (Farber and Peterkin ) have been reported in the U.S.A. Also, several survey results (Bae et al . ; Ding et al . ) reported that the occurrence of L. monocytogenes in fresh vegetables was observed.…”

Evaluation of the microbial contamination of fresh produces and their cultivation environments from farms in Korea

“…Among fresh produce samples, cucumber samples (product, soil, irrigation water) had slightly higher counts of B. cereus or S. aureus (Table 3). S. aureus and B. cereus have been detected on raw vegetables and are known to be carried by food handlers or contaminated soil environment, respectively (Bae et al, 2011;Bartoszewicz et al, 2008;Beuchat, 2002). Related to the detection method, all samples were analyzed for six different pathogens by various isolation methods including the selective agar method, API kit, Latex agglutination test, and 16s rRNA sequencing method (Table 4).…”

“…This resulted in a higher specificity for the 16s rRNA sequencing method with a false-positive rate. According to a study conducted by Bae et al (2011), where the raw vegetable samples were analyzed by selective agar method, a higher number of positive results were obtained with the selective agar method compared with that obtained by the PCR. These identification methods will be useful in screening of various fresh produce for foodborne )14 (7.2%) 0 (0.0%) 0 (0.0%) 7 (3.6%) 0 (0.0%) 0 (0.0%) a…”

Microbial Prevalence and Quality of Organic Farm Produce from Various Production Sites

“…국내에서 유기농 상추, 깻잎, 고추 등에서 L. monocytogenes, Salmonella, E. coli O157:H7, S. aureus, C. sakazakii, V. parahaemolyticus 등이 검출되지 않았다고 한 본 결 과와 같았다 (17,(19)(20). 외국에서는 유기농 상추가 관행농보다 대 장균 검출이 많고 Salmonella 등은 검출되지 않았다고 보고하였 다 (18,26).…”