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3151 > IC6 > Flashcards

IC6 Flashcards

1
Q

Activity of disinfectants

A

Eliminates many or all pathogenic microorganisms, except bacterial spores, on inanimate objects

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2
Q

Classification of disinfectants

A
  1. Chemical sterilants: kill spores with prolonged exposure times (3–12 hours)
  2. High-level disinfectants: kill all microorganisms except large numbers of bacterial spores at shorter exposure periods
  3. Low level disinfectants: kill most vegetative bacteria, some fungi, and some viruses in a practical period of time
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3
Q

Factors affecting the efficacy of disinfection

A
  • prior cleaning of the object;
  • organic and inorganic load present;
  • type and level of microbial contamination;
  • concentration of and exposure time to the germicide;
  • physical nature of the object (e.g., crevices, hinges, and lumens);
  • presence of biofilms;
  • temperature and pH of the disinfection process
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4
Q

Antiseptics Vs Disinfectants

A
  • Antiseptics are germicides applied to living tissue and skin;
  • Disinfectants are antimicrobials applied only to inanimate objects;
  • Antiseptics are used only on the skin and not for surface disinfection;
  • Disinfectants are not used for skin antisepsis because they can injure skin and other tissues.
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5
Q

Term for both antiseptics and disinfectants

A

Biocides

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6
Q

Example of fungi

A

Yeasts / molds

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7
Q

What are prions?

A

misfolded proteins that may transmit their misfolded shape onto normal variants

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8
Q

Why are spores resistant to disinfectants?

A

spore coat and cortex act as a barrier

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9
Q

How does mycobacteria acquire resistance to disinfectants?

A

contains waxy cell wall that prevents disinfectant entry

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10
Q

How does gram negative bacteria acquire resistance to disinfectants?

A

they possess an outer membrane that acts as a barrier to the uptake of disinfectants

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11
Q

Does halving the concentration of the disinfectant mean double the time to achieve disinfection?

A

Not necessarily; not a linear relationship

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12
Q

Most important factor influencing the activity of gaseous disinfectant

A

Relative humidity

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13
Q

Examples of gaseous disinfectant

A

ethanol, chlorine dioxide, and formaldehyde

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14
Q

How does water hardness affect the rate of kill of certain disinfectants?

A

Reduces the rate of kill: divalent cations in the hard water interact with the disinfectant to form insoluble precipitates

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15
Q

Two ways in which organic matter (like serum, blood, pus or fecal ) can interfere with the antimicrobial activity of disinfectants

A

1) Chemical reaction between the germicide -> Reduction in potency or full chemical inactivation

2) Protection by occlusion in salt crystals -> Precipitation or inclusion

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16
Q

Mechanisms that make microbes within biofilms resistant to disinfectants

A

• layers of older biofilms,
• genotypic variation,
• neutralizing enzymes,
• physiologic conditions

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17
Q

Is isopropanol against non-enveloped viruses?

A

No. It is active against enveloped viruses.

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18
Q

MOA for Ammonia (aq)

A

Saponify lipids within envelopes of microorganisms

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19
Q

Is alcohol bacteriostatic/ bactericidal?

A

Bacteriostatic

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20
Q

Concerns for ammonia use

A
  1. Irritant for eyes and gastric system
  2. May release chloramine (toxic) when mixed with bleach
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21
Q

What could be added to enhance alcohol MOA (denaturation of ptns)?

A

Water

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22
Q

MOA for aldehyde

A

Alkylation of sulfhydryl, hydroxyl, carboxyl and amino groups of microorganisms -> alters RNA, DNA & protein synthesis

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23
Q

Concern for aldehyde

A

Toxic and odour

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24
Q

Ppty of Ortho-phthalaldehyde (OPA) that assists its entry to outer layers of mycobacterium & gram-negative bacteria

A

Lipophilicity

25
Q

Advantages and limitations of OPA

A

(+) Excellent stability over wide range of pH 3-9
(+) Not irritant to eyes and nasal passages
(+) Odourless
(+) Excellent material compatibility
(-) Stains protein grey (incl unprotected skin) -> handle with caution

26
Q

Is Chlorhexidine bacteriostatic/ bactericidal?

A

bactericidal

27
Q

Name 2 biguanides

A

Chlorhexidine and alexidine

28
Q

Activity of chlorhexidine is ___ dependent and greatly ____ in the presence of _____.

A

pH; reduced; organic matter

29
Q

Advantages of alexidine over chlorhexidine

A

Faster onset of bactericidal activity & significantly faster alteration in bactericidal permeability compared to chlorhexidine

30
Q

MOA for hypochlorite

A

Oxidation of sulfhydryl enzymes;
Ring chlorination of amino acids;
Inhibition of chlorine synthesis;
DNA disruption;
Loss of intracellular contents

31
Q

Advantages and limitations of hypochlorite

A

(+) Do not leave toxic residues
(+) Unaffected by water hardness
(+) Inexpensive
(+) Fast acting
(+) Removes dried/ fixed organisms and biofilms from surfaces
(+) Low incidence of serious toxicity
(-) Ocular irritation
(-) Burns mouth, throat & stomach
(-) Corrosive to metals in high conc
(-) Inactivation by organic matter
(-) Release of toxic chlorine gas

32
Q

Most widely used chlorine disinfectant

A

Hypochlorite

33
Q

Activity of hypochlorite largely attributed to ______

A

undissociated hypochlorous acid (HOCl)

34
Q

Efficacy of hypochlorite decreases with _______

A

increasing pH (more hypochlorite ion, OCl-)

35
Q

How is Sodium dichloroisocyanurate best prepared? (dosage form)

A

From tablet; stable and long release

36
Q

What contributes to the prolonged effect of Sodium dichloroisocyanurate?

A

Only 50% of available chlorine is free (HOCl and OCl-) and remainder is combined (mono & dichloroisocyanurate) -> remainder released when the free ones are used up

37
Q

Example of iodophor

A

Povidone-iodine

38
Q

MOA for iodophor

A

‘Free’ iodine (I2) penetrate cell wall of microorganism quickly -> disruption of protein & nucleic acid structure and synthesis

39
Q

Dilution of iodophor ____ iodine linkage to _____ which ____ free iodine and ____ action.

A

Weakens; carrier polymer; increases; faster

40
Q

MOA for Hydrogen peroxide
(H2O2)

A

Acts as an oxidant; produces free radical (*OH) which attack essential cell components incl lipids, proteins and DNA

41
Q

Does H2O2 act against spores?

A

Yes; longer contact time to kill spores

42
Q

Presence of _____ in H2O2 render low conc less effective

A

catalase/ peroxidase

43
Q

Concerns for H2O2

A

(-) Short half life (due to decomposition in H2O and H2O2)
(-) Irritant for eyes

44
Q

MOA for Peracetic acid

A

Denatures proteins and enzymes & increases cell wall permeability by disrupting sulfhydryl (-SH) and sulphur (S-S) bonds

45
Q

advantages of peracetic acid

A

(+) Decomposes to safe by-products (acetic acid and oxygen)
(+) Free from decomposition by peroxidase
(+) Remains active in presence of organic loads

46
Q

Peracetic acid is a more potent biocide than _____ at low conc

A

H2O2

47
Q

MOA of phenols

A

Induces progressive leakage of intracellular constituents incl release of K+ (1st index of membrane damage)

48
Q

Example of phenol

A

Chloroxylenol

49
Q

Advantages & limitation of phenol

A

(+) Non-toxic, non-irritant as an excipient in topical products;
(-) toxic upon oral use/ eye contact

50
Q

Example of Silver compounds

A

Silver sulfadiazine (most common) & Silver nitrate

51
Q

Which silver compound has a broader spectrum?

A

Silver sulfadiazine

52
Q

Why is Mercuric chloride (HgCl2) no longer used?

A

(-) Highly toxic and corrosive
(-) Accumulates in kidney -> corrosive damage -> kidney failure

53
Q

Example of QAC

A

Benzalkonium chloride

54
Q

What is Benzalkonium chloride usually used as?

A

antimicrobial preservative

55
Q

Activity of benzalkonium chloride

A

More active against gram positive; minimal activity against endospores & acid-fast bacteria

56
Q

Vapour phase sterilants

A

Ethylene oxide and formaldehyde

57
Q

What could vapour phase sterilants be used on?

A

heat-sensitive medical devices and surgical supplies

58
Q

Uses for UV lamps as disinfectant

A

Mostly used to supplement current hospital or laboratories cleaning and disinfection of contaminated surfaces.

Recently used for water treatment (usually coupled with ion sequestration and chlorine disinfection).

3151 (17 decks)

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