Iodine in a 1:20,000
solution is bactericidal in 1 minute and kills spores in 15 minutes. Tincture
of iodine USP contains 2% iodine and 2.4% sodium iodide in alcohol. It is the
most active antiseptic for intact skin. It is not commonly used because of
serious hyper-sensitivity reactions that may occur and because of its staining
of clothing and dressings.
are complexes of iodine with a surface-active agent such as polyvinyl pyrrolidone (PVP;
povidone-iodine). Iodophors retain the activity of iodine. They kill
vegetative bacteria, myco-bacteria, fungi, and lipid-containing viruses. They
may be spori-cidal upon prolonged exposure. Iodophors can be used as
antiseptics or disinfectants, the latter containing more iodine. The amount of
free iodine is low, but it is released as the solution is diluted. An iodophor
solution must be diluted according to the manufacturer’s directions to obtain
Iodophors are less
irritating and less likely to produce skin hypersensitivity than tincture of
iodine. They require drying time on skin before becoming active, which can be a
disadvantage. Although iodophors have a somewhat broader spectrum of activ-ity
than chlorhexidine, including sporicidal action, they lack its persistent
activity on skin.
is a strong oxidizing agent and universal disinfectant that is most commonly
provided as a 5.25% sodium hypochlorite
solution, a typical formulation for household
bleach. Because formulations may vary, the exact concentration should be
verified on the label. A 1:10 dilution of household bleach provides 5000 ppm of
available chlorine. The CDC recommends this concentration for disinfection of
blood spills. Less than 5 ppm kills vegetative bac-teria, whereas up to 5000
ppm is necessary to kill spores. A con-centration of 1000–10,000 ppm is
tuberculocidal. One hundred ppm kills vegetative fungal cells in 1 hour, but
fungal spores require 500 ppm. Viruses are inactivated by 200–500 ppm.
Dilutions of 5.25% sodium hypochlorite made up in pH 7.5–8.0 tap water retain
their activity for months when kept in tightly closed, opaque containers.
Frequent opening and closing of the container reduces the activity markedly.
Because chlorine is
inactivated by blood, serum, feces, and protein-containing materials, surfaces
should be cleaned before chlorine disinfectant is applied. Undissociated
hypochlorous acid (HOCl) is the active biocidal agent. When pH is increased,
the less active hypochlorite ion, OCl–, is formed. When hypochlorite solutions
contact formaldehyde, the carcinogen bischloromethyl is formed. Rapid evolution
of irritating chlorine gas occurs when hypochlorite solutions are mixed with
acid and urine. Solutions are corrosive to aluminum, silver, and stainless
chlorine-releasing compounds include chlorinedioxide
and chloramine T. These agents
retain chlorine longerand have a prolonged bactericidal action.