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the blood) or febrile reactions due to pyrogenic
construction).
endotoxins from the degradation of the mem-
Bacteriological tests may not always give true esti-
branes of Gram-negative bacteria. The CDC rec-
mates of contamination because of the presence of
ommends that the water for haemodyalisis
agents such as disinfectants.
contain:
less than 200 coliforms/ml for water used for
dilution
Water is used in health care institutions for many
very different uses.
less than 2000 coliforms/ml for dialysate.
The use determines characteristics needed for the
The levels of organisms in dialysate should be
water. These usually differ from those of tap water.
monitored once a month. The coliform recom-
mendations may be revised downwards with
Infections attributable to water are usually due to
improvements in water production, use of dialy-
failure to meet water quality standards for the spe-
sis membranes with improved permeability, and
cific use.
increasing knowledge of the role of bacterial prod-
Infection control/hygiene teams must have written,
ucts in the complications of long-term dialysis.
valid policies for water quality to minimize risk of
New techniques (haemofiltration, haemodialysis
adverse outcomes attributable to water in health care
filtration on line) require stricter guidelines for
settings.
water dilution and for haemodialysis solutions
(9).
8.4 Food
8.3.4 Microbiological monitoring
Quality and quantity of food are key factors for pa-
tient convalescence. Ensuring safe food is an impor-
Regulations for water analysis (at the national level
tant service delivery in health care.
for drinking-water, in the Pharmacopoeia for phar-
maceutical waters) define criteria, levels of impuri-
ties, and techniques for monitoring. For water use
for which regulations are not available, parameters
should be appropriate for the planned use and the
51
PREVENTION OF HOSPITAL-ACQUIRED INFECTIONS: A PRACTICAL GUIDE WHO/CDS/CSR/EPH/2002.12
8.4.1 Agents of food poisoning and foodborne inadequate cooling
infections
inadequate reheating
Bacterial food poisoning (acute gastroenteritis) is an
use of contaminated processed food (cooked
infection or intoxication manifested by abdominal
meats and poultry, pies and take-away meals)
pain and diarrhoea, with or without vomiting or fe-
prepared in premises other than those in which
ver. The onset of symptoms may range from less than
the food was consumed
one to more than 48 hours after eating contami-
undercooking
nated food. Usually, large numbers of organisms
actively growing in food are required to initiate
cross-contamination from raw to cooked food
symptoms of infection or intoxication. Water, milk,
contamination from food handlers.
and solid foods are all vehicles for transmission.
Hospital patients may be more susceptible to food-
Table 3 is a non-exhaustive listing of organisms that
borne infection, and suffer more serious conse-
may cause food poisoning.
quences than healthy people. Thus, high standards
of food hygiene must be maintained. A hospital sur-
TABLE 3. Microbiological agents causing food veillance system must be able to identify potential
poisoning
foodborne outbreaks early (Chapter III), and prompt
outbreak investigation and control must be initi-
Bacteria
ated if an outbreak is suspected (Chapter IV).
Salmonella species Campylobacter jejuni
Staphylococcus aureus Yersinia enterocolitica
Clostridium perfringens Vibrio parahaemolyticus
8.4.3 Prevention of food poisoning
Clostridium botulinum Vibrio cholerae
Bacillus cereus and other Aeromonas hydrophilia
The following food preparation practices must be
aerobic spore-forming Streptococcus species
hospital policy, and rigorously adhered to:
bacilli Listeria monocytogenes
Escherichia coli
Maintain a clean work area.
Separate raw and cooked food to avoid cross-
Viruses Parasites
contamination.
Rotavirus Giardia lamblia
Caliciviruses Entamoeba histolytica
Use appropriate cooking techniques and follow
recommendations to prevent growth of micro-
organisms in food.
8.4.2 Factors contributing to food poisoning
Maintain scrupulous personal hygiene among
The frequency of foodborne illness is increasing. This
food handlers, especially handwashing, as hands
may be due to increasing complexity in modern food
are the main route of contamination (see Chapter
handling, particularly in mass-catering, as well as
6).
increasing importation of potentially contaminated
Staff should change work clothes at least once a
food products from other countries.
day, and keep hair covered.
For individuals to develop food poisoning, the
Avoid handling food in the presence of an infec-
number of organisms in food must be of a sufficient
tious disease (cold, influenza, diarrhoea, vomit-
level. There must also be adequate nutrients, mois-
ing, throat and skin infections), and report all
ture, and warmth for multiplication of organisms,
infections.
or toxin production to occur between preparation
and consumption of the food.
Other factors important for quality control are:
Many inappropriate food handling practices permit
Purchased food must be of good quality (con-
contamination, survival and growth of infecting bac-
trolled), and bacteriologically safe.
teria. The most common errors which contribute to
Storage facilities must be adequate, and corre-
outbreaks include:
spond to requirements for the food type.
preparing food more than a half day in ad-
The quantity of perishable goods should not
vance of needs
exceed an amount corresponding to one day s
storage at room temperature
consumption.
52
CHAPTER VIII. ENVIRONMENT
Dry goods, preserves, and canned food should be 8.5 Waste
stored in dry, well-ventilated storerooms, and
Health care waste is a potential reservoir of patho-
stocks rotated.
genic microorganisms, and requires appropriate han-
Frozen food storage and preparation must follow dling. The only waste which is clearly a risk for
producers instructions, and be kept at tempera- transmission of infection, however, is sharps con-
tures of at least -18 °C (-0.4 °F); do not refreeze. taminated with blood. Recommendations for classi-
fication and handling of different types of waste
The catering system environment must be washed
should be followed (10).
often and regularly with tap water and appropri-
ate detergents (and/or disinfectants).
Samples of prepared food should be stored for a 8.5.1 Definition and classification (10)
specified time period, to allow retrieval for test-
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