Sources of Microorganisms in Foods ◾ 35
of asymptomatically carrying Salmonella Enteritidis in their ovaries and contaminating the yolk
during ovulation. Disease situations, such as mastitis in cows and intestinal, respiratory, and uterine infections as well as injury can change the ecology of normal microflora. Similarly, poor husbandry resulting in fecal contamination on the body surface (skin, hair, feathers, and udder) and
supplying contaminated water and feed (e.g., contaminated with salmonellae) can also change
their normal microbial flora. In addition, stress in farm animals during transportation or resulting
from environmental conditions also can increase the pathogen load in animals before slaughter
and contribute to increased foodborne diseases. 6
Fish and shellfish also carry normal microflora in their scales, skin, and digestive tracts. Water
quality, feeding habits, and diseases can change the normal microbial types and levels. Pathogens,
such as Vibrio parahaemolyticus, Vib. vulnificus, and Vib. cholerae, are of major concern from these
sources. Many spoilage and pathogenic microorganisms can get into foods of animal origin (milk,
eggs, meat, and fishery products) during production and processing. Milk can be contaminated
by fecal materials on the udder surface, eggshells with fecal material during laying, meat with
the intestinal contents during slaughtering, and fish with intestinal contents during processing.
Because of its specific nature, contamination of foods of animal sources with fecal materials is
viewed with concern (possible presence of enteric pathogens).
In addition to enteric pathogens from fecal materials, meat from food animals and birds
can be contaminated with several spoilage and pathogenic microorganisms from skin, hair, and
feathers, namely Staphylococcus aureus, Micrococcus spp., Propionibacterium spp., Campylobacter,
Corynebacterium spp., and molds and yeasts.
Prevention of food contamination from these sources needs the use of effective husbandry of
live animals and birds, which include good housing, avoiding overcrowding, a supply of uncontaminated food and water, and prevention of access to wild animals and birds. Also, testing animals and birds for pathogens and culling the carriers are important in reducing the incidence of
pathogenic microorganisms in foods. Thorough cleansing using good-quality water for washing
carcasses (preferably with acceptable antimicrobial agents); hair removal; feather removal; careful
removal of digestive, urogenital, and respiratory organs without contaminating tissues; removal of
contaminated parts; and proper sanitation during the entire processing stage are necessary during
slaughter to keep microbial quantity and quality at desirable levels. Proper cleaning of the udder
before milking, cooling milk immediately after milking, processing as soon as possible, and sanitization at all stages are important to keep microbial levels low in milk. Eggs should be collected
soon after laying and washed and stored as per recommended procedures.
Fish and marine products should be harvested from unpolluted and recommended water.
Proper sanitation should be used during processing. They should be stored properly to prevent
further contamination and microbial growth. Ice to be used for storage should be produced from
potable water.
Air
Microorganisms are present in dust and moisture droplets in the air. They do not grow in dust
but are transient and variable, depending on the environment. Their levels are controlled by the
degree of humidity, size, and level of dust particles, temperature and air velocity, and resistance of
microorganisms to drying. Generally, dry air with low dust content and higher temperature has a
low microbial level. Spores of Bacillus spp., Clostridium spp., and molds and cells of some Grampositive bacteria (e.g., Micrococcus spp. and Sarcina spp.), as well as yeasts, can be predominantly
present in air. If the surroundings contain a source of pathogens (e.g., animal and poultry farms or
of asymptomatically carrying Salmonella Enteritidis in their ovaries and contaminating the yolk
during ovulation. Disease situations, such as mastitis in cows and intestinal, respiratory, and uterine infections as well as injury can change the ecology of normal microflora. Similarly, poor husbandry resulting in fecal contamination on the body surface (skin, hair, feathers, and udder) and
supplying contaminated water and feed (e.g., contaminated with salmonellae) can also change
their normal microbial flora. In addition, stress in farm animals during transportation or resulting
from environmental conditions also can increase the pathogen load in animals before slaughter
and contribute to increased foodborne diseases. 6
Fish and shellfish also carry normal microflora in their scales, skin, and digestive tracts. Water
quality, feeding habits, and diseases can change the normal microbial types and levels. Pathogens,
such as Vibrio parahaemolyticus, Vib. vulnificus, and Vib. cholerae, are of major concern from these
sources. Many spoilage and pathogenic microorganisms can get into foods of animal origin (milk,
eggs, meat, and fishery products) during production and processing. Milk can be contaminated
by fecal materials on the udder surface, eggshells with fecal material during laying, meat with
the intestinal contents during slaughtering, and fish with intestinal contents during processing.
Because of its specific nature, contamination of foods of animal sources with fecal materials is
viewed with concern (possible presence of enteric pathogens).
In addition to enteric pathogens from fecal materials, meat from food animals and birds
can be contaminated with several spoilage and pathogenic microorganisms from skin, hair, and
feathers, namely Staphylococcus aureus, Micrococcus spp., Propionibacterium spp., Campylobacter,
Corynebacterium spp., and molds and yeasts.
Prevention of food contamination from these sources needs the use of effective husbandry of
live animals and birds, which include good housing, avoiding overcrowding, a supply of uncontaminated food and water, and prevention of access to wild animals and birds. Also, testing animals and birds for pathogens and culling the carriers are important in reducing the incidence of
pathogenic microorganisms in foods. Thorough cleansing using good-quality water for washing
carcasses (preferably with acceptable antimicrobial agents); hair removal; feather removal; careful
removal of digestive, urogenital, and respiratory organs without contaminating tissues; removal of
contaminated parts; and proper sanitation during the entire processing stage are necessary during
slaughter to keep microbial quantity and quality at desirable levels. Proper cleaning of the udder
before milking, cooling milk immediately after milking, processing as soon as possible, and sanitization at all stages are important to keep microbial levels low in milk. Eggs should be collected
soon after laying and washed and stored as per recommended procedures.
Fish and marine products should be harvested from unpolluted and recommended water.
Proper sanitation should be used during processing. They should be stored properly to prevent
further contamination and microbial growth. Ice to be used for storage should be produced from
potable water.
Air
Microorganisms are present in dust and moisture droplets in the air. They do not grow in dust
but are transient and variable, depending on the environment. Their levels are controlled by the
degree of humidity, size, and level of dust particles, temperature and air velocity, and resistance of
microorganisms to drying. Generally, dry air with low dust content and higher temperature has a
low microbial level. Spores of Bacillus spp., Clostridium spp., and molds and cells of some Grampositive bacteria (e.g., Micrococcus spp. and Sarcina spp.), as well as yeasts, can be predominantly
present in air. If the surroundings contain a source of pathogens (e.g., animal and poultry farms or