Fundamental Food Microbiology, Third Edition - Fuad Fathir

436 FUNDAMENTAL FOOD MICROBIOLOGY
A. Characteristics and Habitat
V. ENTEROCOCCUS GROUP
The genus Enterococcus is relatively new and includes many species that were
previously grouped as fecal streptococci and other streptococci. 7–10 They are Grampositive,
nonsporeforming, nonmotile cocci or coccobacilli, catalase negative, and
facultative anaerobes. They can grow between 10 and 45�C, and some species can
grow at 50�C. Some require B vitamins and amino acids for growth. Some can
survive pasteurization temperature. 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 intestine 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.
B. Occurrence and Significance in Food
Enterococcus can get in 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 temperature (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
VI. 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