Indicators of Bacterial Pathogens ◾ 429
This concept is criticized because many species in the Enterobacteriaceae are not of fecal origin; many are found naturally in the environment, including plants, and those that form typical
colonies because of glucose fermentation in the selective medium do not all belong to this family.
However, in heat-processed foods (all are sensitive to pasteurization) and ready-to-eat foods, their
presence in high numbers should have public health significance.
Enterococcus Group
Characteristics and Habitat
The genus Enterococcus is relatively new and includes many species that were previously grouped as
fecal streptococci and other streptococci. 7–10 They are gram-positive, non-spore-forming, nonmotile
cocci or coccobacilli, catalase negative, and facultative anaerobes. They can grow between 10°C and
45°C, and some species can grow at 50°C. Some require B vitamins and amino acids for growth.
Some can survive pasteurization temperatures. In general, they are more resistant than most coliforms
to refrigeration, freezing, drying, low pH, NaCl, and water. They are found in the intestinal tracts
of humans and warm- and cold-blooded animals, birds, and insects. Some can be species specific,
whereas others can be present in humans, warm-blooded animals, and birds. Among the currently
recognized species, several are found in the intestines of humans and food animals and birds, including Enterococcus faecalis, Ent. faecium, Ent. durans, Ent. gallinarum, Ent. avium, and Ent. hirae. Many
have been found in vegetation, processing equipment, and processing environments. Once established,
they can continue to multiply in the equipment and environment and are often difficult to completely
remove. They are found in sewage and water, especially polluted water and mud. They probably do not
multiply in water but can survive longer than many coliforms. They can grow in most foods.
Occurrence and Significance in Food
Enterococcus can enter different foods through fecal contamination or through water, vegetation,
or equipment and processing environments and may not be of fecal origin. In this respect, its
value as an indicator of fecal contamination and possible presence of enteric pathogens in food
is questionable. Also, the ability of some strains to survive pasteurization temperatures (being
thermodurics) reduces their value as an indicator. On the other hand, their better survivability in
dried, frozen, refrigerated, and low-pH foods and water can make them favorable as indicators.
Currently, their presence in high numbers, especially in heat-processed (pasteurized) foods, can be
used to indicate their possible presence in high numbers in raw materials and improper sanitation
of the processing equipment and environment. They have been used to determine the sanitary
quality of water in shellfish beds and are considered to be better as indicators than coliforms
for shellfish. Some strains have also been associated with foodborne gastroenteritis, probably as
opportunistic pathogens. 8–11
Miscellaneous indicator organisms 2
1. Staphylococcus aureus has been used to indicate the extent of human handling in such matrices as foods from food service establishments and fermented meat and dairy products (fermentation failures).
This concept is criticized because many species in the Enterobacteriaceae are not of fecal origin; many are found naturally in the environment, including plants, and those that form typical
colonies because of glucose fermentation in the selective medium do not all belong to this family.
However, in heat-processed foods (all are sensitive to pasteurization) and ready-to-eat foods, their
presence in high numbers should have public health significance.
Enterococcus Group
Characteristics and Habitat
The genus Enterococcus is relatively new and includes many species that were previously grouped as
fecal streptococci and other streptococci. 7–10 They are gram-positive, non-spore-forming, nonmotile
cocci or coccobacilli, catalase negative, and facultative anaerobes. They can grow between 10°C and
45°C, and some species can grow at 50°C. Some require B vitamins and amino acids for growth.
Some can survive pasteurization temperatures. In general, they are more resistant than most coliforms
to refrigeration, freezing, drying, low pH, NaCl, and water. They are found in the intestinal tracts
of humans and warm- and cold-blooded animals, birds, and insects. Some can be species specific,
whereas others can be present in humans, warm-blooded animals, and birds. Among the currently
recognized species, several are found in the intestines of humans and food animals and birds, including Enterococcus faecalis, Ent. faecium, Ent. durans, Ent. gallinarum, Ent. avium, and Ent. hirae. Many
have been found in vegetation, processing equipment, and processing environments. Once established,
they can continue to multiply in the equipment and environment and are often difficult to completely
remove. They are found in sewage and water, especially polluted water and mud. They probably do not
multiply in water but can survive longer than many coliforms. They can grow in most foods.
Occurrence and Significance in Food
Enterococcus can enter different foods through fecal contamination or through water, vegetation,
or equipment and processing environments and may not be of fecal origin. In this respect, its
value as an indicator of fecal contamination and possible presence of enteric pathogens in food
is questionable. Also, the ability of some strains to survive pasteurization temperatures (being
thermodurics) reduces their value as an indicator. On the other hand, their better survivability in
dried, frozen, refrigerated, and low-pH foods and water can make them favorable as indicators.
Currently, their presence in high numbers, especially in heat-processed (pasteurized) foods, can be
used to indicate their possible presence in high numbers in raw materials and improper sanitation
of the processing equipment and environment. They have been used to determine the sanitary
quality of water in shellfish beds and are considered to be better as indicators than coliforms
for shellfish. Some strains have also been associated with foodborne gastroenteritis, probably as
opportunistic pathogens. 8–11
Miscellaneous indicator organisms 2
1. Staphylococcus aureus has been used to indicate the extent of human handling in such matrices as foods from food service establishments and fermented meat and dairy products (fermentation failures).