Bacterial Contamination of Food and How to Avoid It
To prevent the consumption of unsafe food it is essential that contamination is reduced to a minimum. The two most common
types of contamination are:
1. Bacterial contamination, which usually occurs because of poor training, inadequate space, bad design or because food
handlers take short cuts.
2. Physical contamination, by foreign bodies such as glass, metal, wood etc.
Apart from causing a small number of deaths each year, food poisoning results in a huge economic loss to the country in lost
working days and millions of pounds towards treatment by the health services.
Prevention is better than cure and this leaflet is intended to assist businesses in identifying the source and control of common
bacterial hazards that can be found in most food businesses.
Sources, Vehicles and Routes of Contamination
Man, raw foods, insects, animals,
Food or hand-contact
IS FOOD SAFE TO EAT?
Bacteria/Fungi Source Control Risk
Aerobic Colony Environment, including High Standards of hygiene. MEDIUM
Count (ACC) dust, soil Avoid cross-contamination. Indicates hygiene problem
Correct food storage. and will affect quality of
Refrigerate high risk foods (8°C). Monitor product.
Check ‘use by’ dates daily.
Remove damaged packaged goods.
Enterobacteriaceae Human/animal excreta & High standards of hygiene. Frequent hand MEDIUM
raw meat washing. Indicator organism
Avoid cross-contamination highlighting hygiene problem
Escherichia coli Human/animal excreta & High standards of hygiene. Frequent hand HIGH
(E.coli) raw meat. washing. Avoid cross-contamination. Indicator organism
Thorough cooking. Store food at correct highlighting hygiene problem
temperatures. with some strain being
Bacteria/Fungi Source Control Risk
Staphylococcus Humans-nose, skin, Good personal hygiene. Frequent hand HIGH
aureus mouth, hair, boils, cuts washing. Avoid coughing/sneezing over Disease causing pathogen
food. Cover cuts with waterproof
dressings. Avoid handling food – use
utensils. Provide hygienic protective
clothing. Cover arms and use suitable
headwear. Avoid cross-contamination.
Rapid cooling and refrigeration of high risk
Bacillus cereus Cereals, especially rice, Thorough cooking followed by rapid HIGH
dust and soil. cooling. Keep food above 63°C or below
8°C. Avoid re-heating. Avoid cross-
Clostridium Soil, dust, animal and Separate raw from cooked food. High HIGH
perfringens human excreta raw meats standards of hygiene. Thorough cooking – Disease causing pathogen.
and raw vegetables 70°C + rapid cooling and refrigeration (1.5
hrs). Reduce size of joints of meat.
Yersinia spp Animal excreta particularly Frequent hand washing particularly after HIGH
pigs handling raw meat. Eradicate rodent Occasionally causes food
infestation. Exclude pets from food rooms. poisoning in U.K.
Yeasts/Moulds Environment, including High standards of hygiene MEDIUM
dust & soil Correct storage of foods (dry cool well Spoilage, unfit food
ventilated) check for damage to seals or
vacuum packaging. Check ‘use by’ dates
Listeria Found throughout the High standards of hygiene. Correct HIGH
monocytogenes environment including soil storage of high risk food such as pate, soft Particularly pregnant women
& dust cheeses. Check ‘use by’ dates daily.
Listeria spp Found throughout the High standards of hygiene. Good waste MEDIUM
environment including soil water removal. Indicator organism,
& dust. highlighting cleaning
Salmonella Raw meat, milk, eggs, High standards of hygiene. Frequent hand HIGH
poultry, pets, rodents & washing. Avoid cross-contamination e.g. Disease causing pathogen.
insects. wiping cloths, chopping boards.
Refrigerated storage of high risk foods.
Separate raw and cooked foods.
Thorough thawing and cooking of poultry.
Increased use of pasteurised egg. Avoid
raw milk (green top). Exclude pets from
food rooms. Eradicate insect and rodent
infestations. Exclude food handlers who
Campylobacter Raw milk, raw meat, offal, High standards of hygiene. Frequent hand HIGH
poultry, infected animals washing. Avoid cross-contamination. Only small numbers of
e.g. cats & dogs. Exclude pets from food rooms. organisms required to cause
Vibrio spp Humans, raw undercooked Exclude food handlers who are HIGH
seafood from polluted symptomatic (foreign travel frequently Cholera an acute bacterial
waters implicated in countries with poor sanitary illness.