Disinfectants

Disinfectants and Antiseptics
Disinfection denotes the inactivation or
killing of pathogens (protozoa, bacteria,
fungi, viruses) in the human environment.
This can be achieved by chemical
or physical means; the latter will not be
discussed here. Sterilization refers to
the killing of all germs, whether pathogenic,
dormant, or nonpathogenic. Antisepsis
refers to the reduction by chemical
agents of germ numbers on skin and
mucosal surfaces.
Agents for chemical disinfection
ideally should cause rapid, complete,
and persistent inactivation of all germs,
but at the same time exhibit low toxicity
(systemic toxicity, tissue irritancy,
antigenicity) and be non-deleterious to
inanimate materials. These requirements
call for chemical properties that
may exclude each other; therefore,
compromises guided by the intended
use have to be made.
Disinfectants come from various
chemical classes, including oxidants,
halogens or halogen-releasing agents,
alcohols, aldehydes, organic acids, phenols,
cationic surfactants (detergents)
and formerly also heavy metals. The basic
mechanisms of action involve denaturation
of proteins, inhibition of enzymes,
or a dehydration. Effects are dependent
on concentration and contact
time.
Activity spectrum. Disinfectants
inactivate bacteria (gram-positive >
gram-negative > mycobacteria), less effectively
their sporal forms, and a few
(e.g., formaldehyde) are virucidal.
Applications
Skin “disinfection.” Reduction of germ
counts prior to punctures or surgical
procedures is desirable if the risk of
wound infection is to be minimized.
Useful agents include: alcohols (1- and
2-propanol; ethanol 60–90%; iodine-releasing
agents like polyvinylpyrrolidone
[povidone, PVP]-iodine as a depot form
of the active principle iodine, instead of
iodine tincture), cationic surfactants,
and mixtures of these. Minimal contact
times should be at least 15 s on skin areas
with few sebaceous glands and at
least 10 min on sebaceous gland-rich
ones.
Mucosal disinfection: Germ counts
can be reduced by PVP iodine or chlorhexidine
(contact time 2 min), although
not as effectively as on skin.
Wound disinfection can be achieved
with hydrogen peroxide (0.3%–1% solution;
short, foaming action on contact
with blood and thus wound cleansing)
or with potassium permanganate
(0.0015% solution, slightly astringent),
as well as PVP iodine, chlorhexidine,
and biguanidines.
Hygienic and surgical hand disinfection:
The former is required after a suspected
contamination, the latter before
surgical procedures. Alcohols, mixtures
of alcohols and phenols, cationic surfactants,
or acids are available for this purpose.
Admixture of other agents prolongs
duration of action and reduces
flammability.
Disinfection of instruments: Instruments
that cannot be heat- or steamsterilized
can be precleaned and then
disinfected with aldehydes and detergents.
Surface (floor) disinfection employs
aldehydes combined with cationic surfactants
and oxidants or, more rarely,
acidic or alkalizing agents.
Room disinfection: room air and
surfaces can be disinfected by spraying
or vaporizing of aldehydes, provided
that germs are freely accessible.