Investigating Salmonella enterica, Escherichia coli, and Coliforms on Fresh Vegetables Sold in Informal Markets in Cambodia†

Karina Desiree; Carla L Schwan; Visoth Ly; Lyda Hok; Nora M Bello; Londa Nwadike; Randall K Phebus; Jessie L Vipham

doi:10.4315/JFP-20-219

Investigating Salmonella enterica, Escherichia coli, and Coliforms on Fresh Vegetables Sold in Informal Markets in Cambodia†

J Food Prot. 2021 May 1;84(5):843-849. doi: 10.4315/JFP-20-219.

Authors

Karina Desiree^{1

2}, Carla L Schwan^{1

3}, Visoth Ly⁴, Lyda Hok⁵, Nora M Bello⁶, Londa Nwadike⁷, Randall K Phebus^{1

8}, Jessie L Vipham^{1

9}

Affiliations

¹ Department of Animal Sciences and Industry, Food Science Institute, Kansas State University, Manhattan, Kansas 66506, USA.
² https://orcid.org/0000-0001-5910-4195 [K.D.].
³ https://orcid.org/0000-0002-1853-2553 [C.L.S.].
⁴ Faculty of Agro-Industry, Royal University of Agriculture, Phnom Penh, Cambodia.
⁵ Faculty of Agronomy and Center of Excellence on Sustainable Agricultural Intensification and Nutrition, Royal University of Agriculture, Phnom Penh, Cambodia (ORCID: https://orcid.org/0000-0003-2175-1412 [L.H.]).
⁶ Department of Statistics, Kansas State University, Manhattan, Kansas 66506, USA.
⁷ Research and Extension, Kansas State University and University of Missouri, Olathe, Kansas 66061, USA (ORCID: https://orcid.org/0000-0002-4683-0224 [L.N.]).
⁸ https://orcid.org/0000-0003-3427-9751 [R.K.P.].
⁹ https://orcid.org/0000-0002-2918-1058 [J.L.V.].

PMID: 33320940
DOI: 10.4315/JFP-20-219

Abstract

Abstract: Vegetables in Cambodia are commonly sold in informal markets lacking food safety standards and controls. Current data on microbial contamination of vegetables in Cambodian informal markets are limited. The purpose of this study was to investigate Salmonella enterica and indicator organisms (Escherichia coli and coliforms) on the surface of fresh vegetables sold in informal markets in Cambodia. Samples of loose-leaf lettuce, tomatoes, and cucumbers were collected from 104 vendors at four informal markets in Battambang and Siem Reap provinces during the rainy and dry seasons. Detection methods for S. enterica were adapted from the U.S. Food and Drug Administration's Bacteriological Analytical Manual. Coliform and E. coli populations were quantified by plating onto E. coli/coliform count plates. S. enterica was most prevalent on lettuce during the dry season (56.5%, 95% confidence interval [CI] [41.0, 70.8]) than during the rainy season (15.4%, 95% CI [7.5, 29.1]), whereas no significant seasonal differences were apparent for tomatoes and cucumbers. Regardless of season, levels of S. enterica were highest on lettuce (5.7 log CFU/g, 95% CI [5.5, 5.9]), relative to cucumbers (4.2 log CFU/g, 95% CI [3.8, 4.6]) and tomatoes (4.3 log CFU/g, 95% CI [4.1, 4.6]). For E. coli, prevalence was higher during the rainy season (34.0%, 95% CI [25.4, 43.8]) than during the dry season (9.1%, 95% CI [4.9, 16.5]), with the highest prevalence estimated on lettuce. Coliform levels on lettuce and tomatoes were greater during the rainy season (6.3 and 5.3 log CFU/g, 95% CI [5.7, 6.8] and [4.7, 5.8], respectively) than during the dry season (5.2 and 3.9 log CFU/g, 95% CI [4.7, 5.7] and [3.4, 4.4], respectively). These results indicate seasonal patterns for microbial prevalence in lettuce and an overall high level of bacterial contamination on raw vegetables sold in Cambodian informal markets.

Keywords: Escherichia coli; Salmonella enterica; Cambodia; Coliforms; Informal markets; Vegetable safety.

MeSH terms

Cambodia
Colony Count, Microbial
Escherichia coli
Food Contamination / analysis
Food Microbiology
Salmonella enterica*
Vegetables*