Page 912 - Basic _ Clinical Pharmacology ( PDFDrive )

898 SECTION VIII Chemotherapeutic Drugs

TABLE 50–1 Activities of disinfectants.

Bacteria Viruses Other

Gram- Gram- Amebic
Positive Negative Acid-Fast Spores Lipophilic Hydrophilic Fungi Cysts Prions
Alcohols (isopropanol, HS HS S R S V — — R
ethanol)
Aldehydes (glutaraldehyde, HS HS MS S (slow) S MS S — R
formaldehyde)
Chlorhexidine gluconate HS MS R R V R — — R
Sodium hypochlorite, chlorine HS HS MS S (pH 7.6) S S (at high MS S MS (at high
dioxide conc) conc)
Hexachlorophene S (slow) R R R R R R R R
Povidone, iodine HS HS S S (at high S R S S R
conc)
Phenols, quaternary ammo- HS HS MS R S R S — R
nium compounds
conc, concentration; HS, highly susceptible; MS, moderately susceptible; —, no data; R, resistant; S, susceptible; V, variable.

environment or in the body. Disinfectants and antiseptics may tuberculosis, and many fungi, and inactivating lipophilic viruses.
also become contaminated by resistant microorganisms—eg, The optimum bactericidal concentration is 60–90% by volume
spores, P aeruginosa, or Serratia marcescens—and actually transmit in water. They probably act by denaturation of proteins. They
infection. Most topical antiseptics interfere with wound healing are not used as sterilants because they are not sporicidal, do not
to some degree. Cleansing of wounds with soap and water may be penetrate protein-containing organic material, and may not be
less damaging than the application of antiseptics. active against hydrophilic viruses. Their skin-drying effect can be
Some of the chemical classes of antiseptics, disinfectants, and alleviated by addition of emollients to the formulation. Use of
sterilants are described briefly in the text that follows. The reader alcohol-based hand rubs has been shown to reduce transmission
is referred to the general references for descriptions of physical of health care–associated bacterial pathogens and is recommended
disinfection and sterilization methods. by the Centers for Disease Control and Prevention (CDC) as the
preferred method of hand decontamination in health care set-
ALCOHOLS tings. Alcohol-based hand rubs are ineffective against spores of
C difficile, and handwashing with soap and water is required for
The two alcohols most frequently used for antisepsis and dis- decontamination after caring for a patient with infection from
infection are ethanol and isopropyl alcohol (isopropanol). this organism.
They are rapidly active, killing vegetative bacteria, Mycobacterium Alcohols are flammable and must be stored in cool, well-
ventilated areas. They must be allowed to evaporate before cau-
TABLE 50–2 Commonly used terms related to tery, electrosurgery, or laser surgery. Alcohols may be damaging if
chemical and physical killing of applied directly to corneal tissue. Therefore, instruments such as
microorganisms. tonometers that have been disinfected in alcohol should be rinsed
with sterile water, or the alcohol should be allowed to evaporate
Antisepsis Application of an agent to living tissue for the before they are used.
purpose of preventing infection
Decontamination Process that produces marked reduction in
number or activity of microorganisms CHLORHEXIDINE
Disinfection Chemical or physical treatment that destroys
most vegetative microbes and viruses, but not Chlorhexidine is a cationic biguanide with very low water solu-
spores, in or on inanimate surfaces
bility. Water-soluble chlorhexidine digluconate is used in water-
Sanitization Reduction of microbial load on an inanimate based formulations as an antiseptic. It is active against vegetative
surface to a level considered acceptable for bacteria and mycobacteria and has variable activity against fungi
public health purposes
and viruses. It strongly adsorbs to bacterial membranes, causing
Sterilization A process intended to kill or remove all types leakage of small molecules and precipitation of cytoplasmic pro-
of microorganisms, including spores, and usu-
ally including viruses, with an acceptably low teins. It is active at pH 5.5–7.0. Chlorhexidine gluconate is slower
probability of their survival in its action than alcohols, but, because of its persistence, it has
Pasteurization A process that kills nonsporulating microor- residual activity, producing bactericidal action equivalent to alco-
ganisms by hot water or steam at 65–100°C hols. It is most effective against Gram-positive cocci and less active