Food Protection Trends - March/April 2022 - 108

Coliforms are part of Enterobacteriaceae and include
genera such as Citrobacter and Enterobacter and species such
as Escherichia coli (7). These coliforms indicate the possible
presence of pathogenic bacteria (21, 22). This subgroup
makes up approximately 10% of intestinal microflora in
humans and animals, and it is often used as an indication of
hygiene because of its association with fecal contamination
(1, 3). The presence of fecal contamination in food products
and environments may lead to exposure of harmful bacteria
such as pathogenic E. coli or Salmonella (16). These harmful
microorganisms are responsible for a large portion of
diarrheal diseases in developing countries, such as Africa and
Southeast Asia (8).
Approximately one-third of diarrheal-related illness in
developing counties are associated with the consumption of
contaminated food (8, 11, 22). For many of these countries,
however, few studies exist that clearly identify specific etiological
agents (e.g., pathogenic E. coli, Salmonella) responsible
for foodborne disease outbreaks (17). Nevertheless, fresh
produce and other horticulture products have been linked
to foodborne pathogens and outbreaks worldwide (6, 15,
17), and Cambodian diets, such as many of those in South
East Asia, contain many raw fruits and vegetables (12). As in
other countries in the Greater Mekong Subregion, qualitative
assessments of food contamination rates in Cambodia are
still limited and scarce. Understanding how microorganisms
are transmitted along the food production chain might be key
to developing intervention strategies for food safety.
Previous studies conducted within our research group
have provided information about critical contamination
points along the vegetable production chain, specifically at
the informal market level. Samples of three vegetable types
(e.g., lettuce, cucumber, and tomato) and environmental samples
(e.g., food contact and non food-contact surfaces) were
collected at the informal market and analyzed for E. coli and
Salmonella (4, 19). These studies revealed that the prevalence
of E. coli and Salmonella ranged from 9.1 to 56.5% depending
on the season and vegetable type (4), and a vast diversity of
Salmonella enterica serotypes were isolated from environmental
samples (19). In addition, another study from our
research group evaluated the flow and food safety behaviors
of stakeholders in the Cambodian vegetable value chain (5).
This study defined the flow of the vegetables and identified
gaps across the value chain, including deficiencies in food
safety practices in informal markets in Cambodia. Informal
markets represent the main point for retail purchasing a
variety of food products, including vegetables, fruits, meat,
and household items, in Cambodia. Such markets have been
described as locations that " escape effective health and safety
regulations and are often untaxed and unlicensed " (5).
Before reaching retail informal markets, many food products
(e.g., produce) in Cambodia are gathered and collected
in distribution centers before being redistributed to domestic
retailers (e.g., informal markets) and/or international whole108
Food Protection Trends March/April
salers (export of vegetables to Cambodia), such as Thailand
and Vietnam. Produce distribution centers in Cambodia are
a transition point between farmers and informal markets. At
the distribution center level, bulk products such as produce,
meat, and nuts as well as non food products are sold. The
products that are sold at the distribution center can originate
from local farmers, intermediaries, and international
wholesalers (i.e., Vietnam). From the distribution center,
these products may be purchased by collectors, informal
market vendors, restaurant and hotel owners, and household
consumers. The Cambodia vegetable value chain has been
previously described by Sokhen et al. (20).
The objective of this study was to better understand the
role of distribution centers in the safety of produce farm-tofork
continuum by measuring indicator microorganisms that
reflect sanitation and hygiene practices in a major Cambodian
fresh produce distribution center.
MATERIALS AND METHODS
Produce distribution center
The samples described below were collected from the major
and only distribution center in Battambang Province (Fig.
1), located approximately 291 km northwest of Phnom Penh.
The Battambang distribution center is the only distribution
center in the northwestern region; therefore, it represents
one of the main centralized centers in the Cambodia vegetable
value chain.
Sample collection
From each vendor within the distribution center, samples
of three vegetable types were collected-loose-leaf lettuce,
cucumber, and tomato-for a total of 384 samples (tomato,
n = 145; cucumber, n = 132; and lettuce, n = 107). From each
vendor, multiple vegetables of each type were collected and
combined for analysis (e.g., three cucumbers were purchased
from vendor 1, and samples were taken from each cucumber
to reach the desired weight amount [see " Sample preparation " ]).
Samples were collected over a 6-month period
(December 2019-May 2020). Immediately after collection,
vegetables were aseptically transferred into separate, sealable
bags and then labeled and stored in ice. Vegetable samples
were kept at 0 ± 2°C, and temperature was monitored using a
(Cole-Parmer, Vernon Hills, IL) traceable digital thermometer
during transport to the laboratory at Royal University of
Agriculture-Phnom Penh. Samples were received at the lab
within 24 h of collection for microbial analysis.
Sample preparation
The surfaces of lettuce leaves, tomato skins, and cucumber
skins were aseptically excised from each sample with a sterile
scalpel blade, and a 10-g portion from each was weighed
and transferred to individual filter bags (Whirl-Pak, Nasco,
Fort Atkinson, WI). Buffered peptone water (BD, Sparks,
MD) was added to the bag (90 mL), and samples were hand
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