Antiseptics are generally used at lower concentrations than disinfectants because they
Answer: A
Skin and mucous membranes are damaged by the strengths used on floors and instruments, so the same chemical is formulated more gently for tissue. The trade is that an antiseptic is correspondingly less powerful than the disinfectant version.
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Which one of the following is used as a skin antiseptic?
Answer: B
Correct answer: Chlorhexidine
Chlorhexidine is a skin antiseptic: it is active against a broad range of organisms, binds to the skin so that its effect persists for hours after application, and is well tolerated on living tissue. Glutaraldehyde and ethylene oxide are far too toxic for skin and are used on instruments, and full-strength hypochlorite is caustic to tissue.
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Sterilization is required rather than disinfection whenever an item will
Answer: C
An item that breaches the body's barriers can introduce organisms directly into tissue where a few would be enough to cause infection, so nothing viable may remain. Contact with intact skin carries little risk and needs only low-level treatment.
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Autoclaving is unsuitable for oils and powders because steam
Answer: D
Correct answer: cannot penetrate them
Steam sterilises by condensing on the surface it is to sterilise, and an anhydrous oil or a dry powder repels or excludes it, so the interior of the material never sees moist heat at all. Such materials are sterilised by dry heat in a hot air oven instead, which requires a much higher temperature and a much longer time - typically 160 degrees for two hours.
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Which one of the following statements about spores and disinfectants is correct?
Answer: A
Sporicidal activity is the defining feature of the high-level category, and intermediate and low-level agents are not credited with it at all. Some high-level agents, given prolonged contact, are accepted as chemical sterilants.
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Sterility of a processed load is expressed as
Answer: B
Because inactivation is logarithmic, no finite process can prove that nothing survives; the accepted standard is a sterility assurance level, conventionally a one in a million chance of a survivor. That follows directly from the meaning of the D-value.
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Moist heat, dry heat and radiation are classified together as
Answer: C
Correct answer: physical agents
The classification divides sterilising and disinfecting agents into physical - heat in its moist and dry forms, radiation, filtration - and chemical, such as alcohols, aldehydes, halogens and gases. Antiseptics and surfactants are subcategories of the chemical group, so neither can contain heat and radiation.
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The oldest and still most dependable method of sterilization in general use is
Answer: D
Steam under pressure is rapid, reliable, non-toxic, inexpensive and sporicidal, and it penetrates fabrics and porous loads well, which is why it remains the default wherever the item can tolerate heat and moisture. The alternatives exist mainly for items that cannot.
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Sodium hypochlorite loses activity rapidly when
Answer: A
Hypochlorite is consumed by any protein it meets and is broken down by light, so working solutions are made up fresh, kept in dark containers and applied to surfaces that have already been cleaned. Warmth and acidity accelerate its decay further.
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Mercurial compounds have largely been abandoned as antiseptics because they are
Answer: B
Correct answer: toxic and only weakly active
Mercurials such as mercurochrome and thiomersal are bacteriostatic rather than bactericidal, are readily inactivated by organic matter, and carry the toxicity of mercury with its environmental persistence. The combination of modest benefit and real harm is what displaced them once effective alternatives such as chlorhexidine and povidone-iodine became available.
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