Activity of disinfectants
Eliminates many or all pathogenic microorganisms, except bacterial spores, on inanimate objects
Classification of disinfectants
- Chemical sterilants: kill spores with prolonged exposure times (3–12 hours)
- High-level disinfectants: kill all microorganisms except large numbers of bacterial spores at shorter exposure periods
- Low level disinfectants: kill most vegetative bacteria, some fungi, and some viruses in a practical period of time
Factors affecting the efficacy of disinfection
- 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
Antiseptics Vs Disinfectants
- 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.
Term for both antiseptics and disinfectants
Biocides
Example of fungi
Yeasts / molds
What are prions?
misfolded proteins that may transmit their misfolded shape onto normal variants
Why are spores resistant to disinfectants?
spore coat and cortex act as a barrier
How does mycobacteria acquire resistance to disinfectants?
contains waxy cell wall that prevents disinfectant entry
How does gram negative bacteria acquire resistance to disinfectants?
they possess an outer membrane that acts as a barrier to the uptake of disinfectants
Does halving the concentration of the disinfectant mean double the time to achieve disinfection?
Not necessarily; not a linear relationship
Most important factor influencing the activity of gaseous disinfectant
Relative humidity
Examples of gaseous disinfectant
ethanol, chlorine dioxide, and formaldehyde
How does water hardness affect the rate of kill of certain disinfectants?
Reduces the rate of kill: divalent cations in the hard water interact with the disinfectant to form insoluble precipitates
Two ways in which organic matter (like serum, blood, pus or fecal ) can interfere with the antimicrobial activity of disinfectants
1) Chemical reaction between the germicide -> Reduction in potency or full chemical inactivation
2) Protection by occlusion in salt crystals -> Precipitation or inclusion
Mechanisms that make microbes within biofilms resistant to disinfectants
• layers of older biofilms,
• genotypic variation,
• neutralizing enzymes,
• physiologic conditions
Is isopropanol against non-enveloped viruses?
No. It is active against enveloped viruses.
MOA for Ammonia (aq)
Saponify lipids within envelopes of microorganisms
Is alcohol bacteriostatic/ bactericidal?
Bacteriostatic
Concerns for ammonia use
- Irritant for eyes and gastric system
- May release chloramine (toxic) when mixed with bleach
What could be added to enhance alcohol MOA (denaturation of ptns)?
Water
MOA for aldehyde
Alkylation of sulfhydryl, hydroxyl, carboxyl and amino groups of microorganisms -> alters RNA, DNA & protein synthesis
Concern for aldehyde
Toxic and odour
Ppty of Ortho-phthalaldehyde (OPA) that assists its entry to outer layers of mycobacterium & gram-negative bacteria
Lipophilicity
