430 ◾ Fundamental Food Microbiology
2. Listeria species have been used to indicate the effectiveness of sanitation programs in food
production facilities for ready-to-eat refrigerated products.
3. Salmonella enterica has been used to indicate control of enteric bacteria in raw meat and
poultry.
4. Coliphages have been used to indicate the effectiveness of enteric virus control in water and
shellfish.
5. The thermophilic bacilli (such as Anoxybacillus flavithermus and Geobacillus spp.) have been
used to indicate poor hygienic practices during dairy processing. Growth of these indicators
in milk can also cause product defect and off flavor. 12
Conclusion
In food microbiology, the concept of indicator bacteria was introduced to measure the sanitary
quality of pasteurized foods (e.g., milk). Its purpose was to indicate the possible presence of enteric
pathogens (e.g., Salmonella) in the food. Over time, the suitability of several bacterial groups has
been considered and this aspect has been discussed in this chapter. It is apparent that selection of
a suitable indicator and its level may change with food types and for raw, processed, and readyto-eat foods.
QUESTIONS
1. Discuss the need of using indicator bacteria for enteric pathogens in food.
2. List, with brief explanations, six criteria that should be considered in selecting an indicator
of enteric pathogens.
3. Which foodborne pathogens are generally not considered enteric? Why? What could be
done to determine their possible presence in a food?
4. What are some similarities and differences in characteristics between coliforms and fecal
coliforms? What is the significance of their presence in high numbers (≥10 4 /g or /mL) and
low numbers (≤10 1 /g or mL) in a raw food, in a pasteurized food, and in a ready-to-eat food?
5. Why are fecal coliforms considered a better indicator of enteric pathogens than are coliforms?
6. What are the advantages and disadvantages of using Esc. coli as an indicator of enteric pathogens in food? “An indicator should be present when an enteric pathogen is present in a food.”
Why might this statement not be valid for Esc. coli as an indicator?
7. List the conditions under which coliforms, fecal coliforms, and Esc. coli have questionable
values as indicators of enteric pathogens.
8. What are the justifications of using the Enterobacteriaceae family as indicators? What are
the disadvantages of using this group as an indicator of enteric pathogens?
9. List some characteristics of enterococci that put them in an advantageous position over coliforms as indicators of enteric pathogens. What are the disadvantages of using enterococci as
indicators?
10. Oyster-harvesting waterbeds in rivers are often closed because of high levels of indicator
bacteria. Explain the advantages and disadvantages of using fecal coliforms and enterococci
as sanitary indicators in water samples, mud, and oyster meat.
2. Listeria species have been used to indicate the effectiveness of sanitation programs in food
production facilities for ready-to-eat refrigerated products.
3. Salmonella enterica has been used to indicate control of enteric bacteria in raw meat and
poultry.
4. Coliphages have been used to indicate the effectiveness of enteric virus control in water and
shellfish.
5. The thermophilic bacilli (such as Anoxybacillus flavithermus and Geobacillus spp.) have been
used to indicate poor hygienic practices during dairy processing. Growth of these indicators
in milk can also cause product defect and off flavor. 12
Conclusion
In food microbiology, the concept of indicator bacteria was introduced to measure the sanitary
quality of pasteurized foods (e.g., milk). Its purpose was to indicate the possible presence of enteric
pathogens (e.g., Salmonella) in the food. Over time, the suitability of several bacterial groups has
been considered and this aspect has been discussed in this chapter. It is apparent that selection of
a suitable indicator and its level may change with food types and for raw, processed, and readyto-eat foods.
QUESTIONS
1. Discuss the need of using indicator bacteria for enteric pathogens in food.
2. List, with brief explanations, six criteria that should be considered in selecting an indicator
of enteric pathogens.
3. Which foodborne pathogens are generally not considered enteric? Why? What could be
done to determine their possible presence in a food?
4. What are some similarities and differences in characteristics between coliforms and fecal
coliforms? What is the significance of their presence in high numbers (≥10 4 /g or /mL) and
low numbers (≤10 1 /g or mL) in a raw food, in a pasteurized food, and in a ready-to-eat food?
5. Why are fecal coliforms considered a better indicator of enteric pathogens than are coliforms?
6. What are the advantages and disadvantages of using Esc. coli as an indicator of enteric pathogens in food? “An indicator should be present when an enteric pathogen is present in a food.”
Why might this statement not be valid for Esc. coli as an indicator?
7. List the conditions under which coliforms, fecal coliforms, and Esc. coli have questionable
values as indicators of enteric pathogens.
8. What are the justifications of using the Enterobacteriaceae family as indicators? What are
the disadvantages of using this group as an indicator of enteric pathogens?
9. List some characteristics of enterococci that put them in an advantageous position over coliforms as indicators of enteric pathogens. What are the disadvantages of using enterococci as
indicators?
10. Oyster-harvesting waterbeds in rivers are often closed because of high levels of indicator
bacteria. Explain the advantages and disadvantages of using fecal coliforms and enterococci
as sanitary indicators in water samples, mud, and oyster meat.