Fundamental Food Microbiology, Third Edition - Fuad Fathir

422 FUNDAMENTAL FOOD MICROBIOLOGY
or returning from it can bring a new foodborne pathogen into a country where it
was not recognized previously. Esc. coli, associated with traveler’s diarrhea, and Vib.
cholerae non-01 (new serotype) were probably introduced to the U.S. this way. 1–4,15
Another important factor is changes in food habits. In the U.S., increased consumption
of seafoods, some of which are eaten raw, have resulted in an increase in
foodborne disease outbreaks by Vib. parahaemolyticus, Vib. vulnificus, Vib. cholerae,
and Hepatitis A, all of which were not always recognized as foodborne pathogens.
Similarly, consumer preferences for low-heat-processed foods with a long shelf life
at refrigerated temperatures has enhanced the chances of psychrotrophic pathogens
(e.g., Lis. monocytogenes and Yer. enterocolitica) becoming important foodborne
pathogens. Several food preferences, such as consumption of raw milk and undercooked
hamburgers, provided the right consequences for Cam. jejuni and Esc. coli
O157:H7, respectively, to cause foodborne disease outbreaks. Similarly, preference
for some imported foods, especially the ready-to-eat type, can introduce a new
pathogen. An example is the incidence of enterotoxigenic Esc. coli O27:H20 from
the consumption of a variety of imported contaminated cheeses in the U.S. 1–4,15
How a change in food consumption patterns can change the profile of foodborne
diseases is best exemplified by an increase in foodborne diseases from the increase
in consumption of minimally processed ready-to-eat foods. According to a survey
by Information Resource, Inc., convenience food continues to be the priority for
U.S. consumers. The data show the food preference as follows: ready-to-eat, 77%;
heat-and-eat, 76%; packaged for on-the-go consumption, 65%; and no utensils
required, 64%. In addition to these, the preference for foods that are more natural
has encouraged the production of large varieties of minimally processed foods. Many
of these are fresh or given a low-heat treatment and expected to have a shelf life of
3 to 10 weeks or more at refrigerated temperature. Chapter 20 gives examples of
many psychrotrophic bacteria being associated with the spoilage of minimally processed
foods. Most of these spoilage bacteria gain access to the products as postheat
contaminants, generally in low number; during long storage, they multiply to reach
the spoilage detection levels. Many of them are new spoilage bacteria or bacteria
not previously suspected to be spoilage bacteria. A similar situation can exist for
the presence of pathogens in minimally processed foods. The storage temperature
of these products ranges from 4 to 15�C or more (during display). Psychrotrophic
and many mesophilic pathogens can multiply during storage and from a very low
contamination level (e.g., ca. 1/25g) reach to hazard potential level.
Since 1990, there has been an increase in consumption of ready-to-eat raw
vegetables (salads), and fruits (fruit juices). Surprisingly, foodborne disease incidence
from these sources has increased (Table 28.4). 16,17 Before the 1990s, many of
these vegetables and fruits were not considered to be associated with so many
different types of foodborne diseases, many of which are thought to be caused by
emerging pathogens. Large quantities of this produce come from many countries;
often it is difficult to determine the source of production because of complexities
involved in international trade. The major sources of contamination are the lack of
field sanitation, use of poor-quality water for washing, transportation in dirty trucks,
and lack of sanitation in handling the produce. 16,17 Controlled studies showed that
many pathogens can not only survive but also grow in fresh vegetables and fruit and