Fundamental Food Microbiology, Third Edition - Fuad Fathir

426 FUNDAMENTAL FOOD MICROBIOLOGY
There are some concerns that use of unrestricted antibiotics in animals has
provided the antibiotic-resistant pathogens with a better chance of competing with
the sensitive microorganisms and establishing themselves in the environment. In the
absence of competition, these pathogens can predominate and, through contamination
of a food, emerge as new foodborne pathogens. Such an assumption was made
against some sanitary practices used in the processing and handling of foods. Some
of the practices are designed to overcome problems from pathogenic and spoilage
bacteria traditionally suspected to be present in a food. Elimination of these predominant
bacteria may allow minor as well as poorly competing bacteria to become
significant in the absence of competition and subsequently cause problems. However,
this is probably more important in the case of food spoilage bacteria and has been
discussed in Chapter 21.
In recent years, consumption of several low-pH foods, such as orange and apple
juices, and fermented sausages, has been implicated in foodborne diseases caused
by Esc. coli O157:H7, Salmonella, and Lis. monocytogenes. These pathogens are
normally sensitive to low pH (pH £ 4.5) and are expected to die-off rapidly during
storage at refrigerated temperature. Studies showed that the pathogens isolated from
these foods are acid-resistant variants and are thus able to survive well in a low-pH
product (see Chapter 9). Stress response can enable pathogens to survive in food
through many processing conditions and make the food potentially hazardous.
There is also some speculation that present methods of raising and feeding food
animals and birds may have given some pathogens a better chance to become
established as carriers in the animals and birds. Food from these sources has a greater
chance of being contaminated with these pathogens. The occurrence of Esc. coli
O157:H7 in hamburger meat prepared from culled dairy cows and the high incidence
of Salmonella Enteritidis in eggs and chickens could be due, in part, to the way they
are raised now.
Finally, people who are immunocompromised can easily become ill from consuming
a food contaminated with a pathogen, even at a low dose level. People with
normal resistance will have no problem the same food. This is particularly true for
opportunistic pathogens. Some, such as Aer. hydrophila and Ple. shigelloides, are
currently implicated indirectly as possible foodborne pathogens. In the future, people
with low immunity may be found to become ill from consuming a food contaminated
with an opportunistic pathogen, which then will become a new foodborne pathogen.
16,17
III. CONCLUSION
The designation new and emerging foodborne pathogen may be inappropriate,
because many of the so-called new pathogens have been contaminating foods for a
long time. For one reason or another, their presence in food has not been examined.
Several socioeconomic patterns and lifestyles of consumers have increased the
chances of such pathogens being involved in foodborne outbreaks. Scientific understanding
and advancement have helped to recognize these chances. In the future,
more pathogens, especially viruses, will be in this “new” group and foods will have
to be tested for them.