9. Disinfection
9.8 BACTERIA, STERILIZATION, AND DISINFECTION
9.8.1 Definitions
9.8.1.1 Bacterium
A bacterium is a member of a class of microscopic organisms
having a round, rodlike, spiral, or filamentous single-celled body.
It grows in colonies or moves by means of long, whip-like
appendages called flagella. Some create their own food, absorb
dissolved organic material, or feed on the host organism. Bacteria
are important to humans because of their chemical effects, and
because they often cause disease. (Webster's, 1991) Simply put,
they are microscopic plants or animals, some of which have the
ability to cause disease in humans if provided the correct
environment. Sometimes they are referred to as microorganisms.
9.8.1.2 Sterilization
Sterilization means a chemical or physical treatment which
inactivates (killing or inhibiting reproduction) all living and
vegetative microorganisms.
Strictly speaking, absolute sterility does not exist and it should in
fact be expressed in terms of "probability of survival". In other
words, given a certain initial bacterial load, one evaluates the
probability of finding still viable microorganisms after a specific
sterilization treatment.
With sterile disposable devices, for example, a survival probability
of 10
-6
is commonly accepted, which equals one contaminated
device in a million.
The more reduced initial contamination is, the lower the risk of
residual contamination after a sterilization treatment.
9.8.1.3 Disinfection
Disinfection means the chemical or physical process which affects
living microorganisms, but has little efficacy on vegetative forms.
Taking into account that a large part of the microorganisms
pathogenic to man do not have vegetative forms (spores),
disinfection is a treatment which because of its simplicity and
rapidity may prove useful in numerous situations of prevention of
microbic contamination. In the hospital environment, or more
precisely, in departments with a high risk of contamination,
prevention and prophylaxis are certainly a standard to pursue to
obtain a level of quality which will produce greater benefits to the
patient, the hospital staff and the society. The problem of
disinfection is particularly critical during dialysis, where a large
157-1278-916, Rev A 9-33
March 2004
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