RESEARCH PAPER
 
KEYWORDS
TOPICS
ABSTRACT
Objective:
The aim of the study was to determine the presence and concentration of indicator microorganisms on leafy green vegetables available in Poland.

Material and methods:
Microbial analyses of 122 samples of leafy green vegetables: rocket, lamb’s lettuce, iceberg lettuce, chive, spinach, celery, dill and parsley, sold in Polish supermarkets in 2018 and 2019, were conducted. The vegetables were analyzed for aerobic mesophilic bacteria, yeasts and moulds, Enterobacteriaceae, Enterococcus, coliforms and Escherichia coli number according to Polish standards.

Results:
The most microbiologically contaminated vegetables occurred to be parsley, rocket and spinach, and the least contaminated was iceberg lettuce. The presence of total mesophilic bacteria was found in all samples. The highest average number of mesophilic bacteria was found for lamb’s lettuce, rocket, parsley and spinach. Numerous yeasts were presented in almost all leafy green samples while rocket and parsley were the most contaminated with moulds. Enterobacteriaceae were isolated from all samples of parsley. High populations of these bacteria were found in rocket and celery samples. Of the 122 vegetable samples, 95 (78%) were positive for coliforms, especially all samples of parsley were inhabited by these bacteria. 24% of all samples were contaminated by Enterococcus, mainly parsley, spinach and chive. The presence of E. coli was found in only one sample of spinach.

Conclusions:
The levels of aerobic mesophilic bacteria, yeasts and moulds, Enterobacteriaceae, Enterococcus and coliforms in leafy green vegetables sold in Poland could be classified as moderate or low. The abundant presence of the studied microorganisms may pose a risk for some categories of people consuming leafy green vegetables, mostly immuno-compromised persons.

ACKNOWLEDGEMENTS
This study was financed by the Polish Ministry of Education and Science (Project No. ZM/2/2018–2018–2023: ‘Development methods limiting the occurrence of microbiological contamination of ready-to-eat vegetables and fruit.” The authors express their thanks to Anna Michalska and Jolanta Winciorek for their technical assistance.
 
REFERENCES (51)
1.
Stea TH, Nordheim O, Bere E, et al. Fruit and vegetable consumption in Europe according to gender, educational attainment and regional affiliation – A cross-sectional study in 21 European countries. PLoS One. 2020;15(5):e0232521. https://doi.org/10.1371/journa....
 
2.
Callejón RM, Rodríguez-Naranjo MI, Ubeda C, et al. Reported foodborne outbreaks due to fresh produce in the United States and European Union: trends and causes. Foodborne Pathog Dis. 2015;12 (1):32–38.
 
3.
Alegbeleye OO, Singleton I, Sant’Ana AS. Sources and contamination routes of microbial pathogens to fresh produce during field cultivation: A review. Food Microbiol. 2018;73:177–208. https://doi.org/10.1016/j.fm.2....
 
4.
Critzer FJ, Doyle MP. Microbial ecology of foodborne pathogens associated with produce. Curr Opin Biotechnol. 2010;21:125–130. https://doi.org/10.1016/j.copb....
 
5.
Machado-Moreira B, Richards K, Brennan F, et al. Microbial contamination of fresh produce: what, where, and how? Compr Rev Food Sci Food Saf. 2019;18:1727–1750. https://doi.org/10.1111/1541-4....
 
6.
Herman KM, Hall AJ, Gould LH. Outbreaks attributed to fresh leafy vegetables, United States, 1973–2012. Epidemiol Infect. 2015;143(14):3011–3021. https://doi.org/10.1017/S09502....
 
7.
Dees MW, Lysoe E, Nordskog B, et al. Bacterial communities associated with surfaces of leafy greens: shift in composition and decrease in richness over time. Appl Environ Microbiol. 2015;81(4):1530–1539. https://doi.org/10.1128/AEM.03....
 
8.
Denis N, Zhang H, Leroux A, et al. Prevalence and trends of bacterial contamination in fresh fruits and vegetables sold at retail in Canada. Food Control. 2016;67:225–234. https://doi.org/10.1016/j.food....
 
9.
Riggio GM, Wang Q, Kniel KE, et al. Microgreens – A review of food safety considerations along the farm to fork. Int J Food Microbiol. 2019;290:76–85. https://doi.org/10.1016/j.ijfo....
 
10.
Rosberg AK, Darlison J, Morgen L, et al. Commercial wash of leafy vegetables do not significantly decrease bacterial load but leads to shifts in bacterial species composition. Food Microbiol. 2021;94:103667. https://doi.org/10.1016/j.fm.2....
 
11.
Ssemanda JN, Reij M, Bagabe MC, et al. Indicator microorganisms in fresh vegetables from “farm to fork” in Rwanda. Food Control. 2017;75:126–133. https://doi.org/10.1016/j.food....
 
12.
Szczech M, Kowalska B, Smolińska U, et al. Microbial quality of organic and conventional vegetables from Polish farms. Int J Food Microbiol. 2018;286:155–161 http://doi.org/10.1016/j.ijfoo....
 
13.
Zheng J, Kase J, De Jesus A, et al. 2017. Microbial ecology of fresh vegetables, in: Souza Sant’Ana A. (Ed), Quantitative Microbiology in Food Processing: Modeling the Microbial Ecology. John Willey & Sons, Ltd. pp. 341–357.
 
14.
Chajęcka-Wierzchowska W, Zadernowska A, Łaniewska-Trokenheim Ł. Virulence factors of Enterococcus spp. presented in food. LWT- Food Sci Technol. 2017;75:670–676. https://doi.org//10.1016/j.lwt....
 
15.
Berger CN, Sodha SV, Shaw RK, et al. Fresh fruit and vegetables as vehicles for the transmission of human pathogens. Environ Microbiol. 2010;12(9):2385–2397. https://doi.org/10.1111/j.1462....
 
16.
Elias SO, Noronfa TB, Tondo EC. Salmonella spp. and Escherichia coli O157:H7 prevalence and levels on lettuce: A systematic review and meta-analysis. Food Microbiol. 2019;84:103217. https://doi.org/10.1016/j.fm.2....
 
17.
Erickson MC. Microbial risks associated with cabbage, carrots, celery, onions, and deli salads made with these produce items. Compr Rev Food Sci Food Saf. 2010;9:602–619. https://doi.org/10.1111/j.1541....
 
18.
Ge Ch, Lee Ch, Lee J. The impact of extreme weather events on Salmonella internalization in lettuce and green onion. Food Res Int. 2012;45:1118–1122. https://doi.org/10.1016/j.food....
 
19.
Leff JW, Fierer N. Bacterial communities associated with the surfaces of fresh fruits and vegetables. PLoS One. 2013;8(3):e59310. https://doi.org/10.1371/journa....
 
20.
Schikora A, Garcia AV, Hirt H. Plants as alternative hosts for Salmonella. Trends Plant Sci. 2012;17(5):245–249. https://doi.org/10.1016/j.tpla....
 
21.
Smith A, Hearn J, Taylor C, et al. Listeria monocytogenes isolates from ready to eat plant produce are diverse and have virulence potential. Int J Food Microbiol. 2019;299:23–32. https://doi.org/ 10.1016/j.ijfoodmicro.2019.03.013.
 
22.
Szymczak B, Sawicki W, Bogusławska-Wąs E, et al. Occurrence of L. monocytogenes in fresh fruits and vegetables from organic farmers in west pomeranian region. ŻNTJ. 2011; 2(75):67–76. In Polish with English summary.
 
23.
Enikova RK, Stoyonovska MR, Karcheva MD. Mycotoxins in fruits and vegetables. J of IMAB. 2020;26(2):3139–3143. https://doi.org/10.5272/jimab.....
 
24.
Kakde U, Kakde HU. Incidence of post-harvest disease and airborne fungal spores in a vegetable market. Acta Bot Croat. 2012;71(1):147–157.
 
25.
Carballo D, Molt? JC, Berrada H, et al. Presence of mycotoxins in ready-to-eat food and subsequent risk assessment. Food Chem Toxicol. 2018;121:558–565. https://doi.org/10.1016/j.fct.....
 
26.
Żukiewicz-Sobczak W, Cholewa G, Sobczak P, et al. Health risks associated with exposure to fungi. Agric Agric Sci Proc. 2015;7:313–317. doi.10.1016/j.aaspro.2015.12.053.
 
27.
Marinelli L, Maggi O, Aurigemma C, et al. Fresh vegetables and ready-to eat salad: phenotypic characterization of moulds and molecular characterization of yeasts. Annali di Igiene: Medicina Preventiva e di Comunita. 2012;24:1.
 
28.
Saleh I, Al-Thani R. Fungal food spoilage of supermarkets’ displayed fruits. Vet World. 2019;12(11):1877–1883. https://doi.org/10.14202/vetwo....
 
29.
Sani NM, Salihu Y, Saidu AY, et al. Isolation of fungi associated with spoilage of selected vegetables sold in Dutse-Ultra modern market, Jigawa State, Nigeria. DUJOPAS. 2018;4(2):349–356.
 
30.
Gil MI, Selma MV, Suslow T, et al. Pre- and postharvest preventive measures and intervention strategies to control microbial food safety hazards of fresh leafy vegetables. Crit Rev Food Sci Nutr. 2015;55:453–468. https://doi.org/10.1080/104083....
 
31.
Qadri OS, Yousuf B, Srivastava AK. Fresh-cut fruits and vegetables: Critical factors influencing microbiology and novel approaches to prevent microbial risks – A review. Cogent Food Agric. 2015;1:1121606. https://doi.org/10.1080/233119....
 
32.
Holvoet K, Sampers I, Seynnave M, et al. Relationships among hygiene indicators and enteric pathogens in irrigation water, soil and lettuce and the impact of climatic conditions on contamination in the lettuce primary production. Int J Food Microbiol. 2014;171:21–31. https://doi.org/10.1016/j.ijfo....
 
33.
Julien-Javaux F, Gerard C, Campagnoli M, et al. Strategies for the safety management of fresh produce from farm to fork. Curr Opin Food Sci. 2019;27:145–152. https://doi.org/10.1016/j.cofs....
 
34.
Ssemanda JN, Reij M, Middendorp G, et al. Foodborne pathogens and their risk exposure factors associated with farm vegetables in Rwanda. Food Control. 2018;89:89–96. https://doi.org/10.1016/j.food....
 
35.
Faur-Klingbeil D, Murtada M, Kuri V. Understanding the routes of contamination of ready-to-eat vegetables in the Middle East. Food Control. 2016;62:125–133. https://doi.org/10.1016/j.food....
 
36.
Mandrell RE. Enteric human pathogens associated with fresh produce: sources, transport, and ecology. In: Fan X, Niemira BA, Doona CJ, et al. editors. Microbial safety of fresh produce. Willey-Blackwell publisher; 2009. p. 5–41.
 
37.
Beaulieu JC. Factors affecting sensory quality of fresh-cut produce. In: Martin-Belloso O, Soliva-Fortuny R, editors. Advances in Fresh-Cut Fruits and Vegetables Processing. CRC Press, Taylor and Francis, Boca Raton, FL., United States of America; 2011. p. 115–143.
 
38.
Badosa E, Trias R, Pares D, et al. Microbiological quality of fresh fruit and vegetable products in Catalonia (Spain) using normalized plate-counting methods and real time polymerase chain reaction (QPCR). J Sci Food Agric. 2008;88:605–611.
 
39.
Korir RC, Parveen S, Hashem F, et al. Microbiological quality of fresh produce obtained from retail stores on the Eastern shore of Maryland, United States of America. Food Microbiol. 2016;56:29–34. https://doi.org/10.1016/j.fm.2....
 
40.
Kłapeć T, Cholewa A, Cholewa G, et al. Microbiological characterization of vegetables and their rhizosphere soil in Eastern Poland. Ann Agric Environ Med. 2016;23(4):559–565. https://doi.org/10.5604/123219....
 
41.
Wójcik-Stopczyńska B, Jadczak D, Kotula A. Microbiological quality of fresh and frozen New Zealand spinach (Tetragonia expansa Murray). ZPPNR. 2008;527:317–326. In Polish with English summary.
 
42.
Hou Z, Fink RC, Radtke C, et al. Incidence of naturally internalized bacteria in lettuce leaves. Int J Food Microbiol. 2013;162:260–265. https://doi.org/10.1016/j.ijfo....
 
43.
Merlini VV, Pena FL, Cunha DT, et al. Microbiological quality of organic and conventional leafy vegetables. J Food Qual. 2018;4908316. https://doi.org/10.1155/2018/4....
 
44.
Caponigro V, Ventura M, Chiancone I, et al. Variation of microbial load and visual quality of ready-to-eat salads by vegetable type, season, processor and retailer. Food Microbiol. 2010;27:1071–1077. https://doi.org/10.1016/j.fm.2....
 
45.
Oladele, Olakunle O. Microorganisms associated with the deterioration of fresh leafy Indian spinach in storage. J Plant Pathol Microbiol. 2011;2:110. https://doi.org/10.4172/2157-7....
 
46.
Ismaiel AA, Papenbrock J. Mycotoxins: producing fungi and mechanisms of phytotoxicity. Agriculture. 2015;5:492–537. https://doi.org/10.3390/agricu....
 
47.
Bartz FE, Lickness JS, Heredia N, et al. Contamination of fresh produce by microbial indicators on farms and in packing facilities: elucidation of environmental routes. Appl Environ Microbiol. 2017;83(11):e0984–16. doi:10.1128/AEM.02984-16.
 
48.
Quansah JK, Kunadu AP-H, Saalia FK, et al. Microbial quality of leafy green vegetables grown or sold in Accra metropolis, Ghana. Food Control. 2018;86:302–309. https://doi.org/10.1016/j.food....
 
49.
Delbeke S, Ceuppens S, Jacxsens L, et al. Microbiological analysis of pre-packed sweet basil (Ocimum basilicum) and coriander (Coriandrum sativum) leaves for the presence of Salmonella spp. and Shiga toxin-producing E. coli. Int J Food Microbiol. 2015;208:11–18. https://doi.org/10.1016/j.ijfo....
 
50.
EC/2073/2005. Commission Regulation (EC) No 2073/2005 of 15 November 2005 on microbiological criteria for foodstuffs. Off. J. Eur. Union. Available at: http://eur-lex. europa.eu/LexUriServ/LexUriSer....
 
51.
De Quadros Rodrigues R, Loiko MR, Mineia Danie de Paula C, et al. Microbiological contamination linked to implementation of good agricultural practices in the production of organic lettuce in Southern Brazil. Food Control. 2014;42:152–164. https://doi.org/10.1016/j.food....
 
eISSN:1898-2263
ISSN:1232-1966