Disinfectant Efficacy: Understanding the Expectations and How to Design Effective Studies That Include Leveraging Multi-Site Data to Drive an Efficient Program

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Figure 1
PDCA cycle for a successful disinfection program

TABLE I

General Classification of Antiseptics, Disinfectants, and Sporicidal Agents^{^a}

Chemical Entity	Classification	Example
Aldehydes	Sporicidal agent	2% Glutaraldehyde
Alcohols	General purpose disinfectant, antiseptic, antiviral agent	70% Isopropyl alcohol, 70% alcohol
Chlorine and sodium hypochlorite	Sporicidal agent	0.5% Sodium hypochlorite
Phenolics	General purpose disinfectant	500 µg per gram Chlorocresol, 500 µg per gram chloroxylenol
Ozone	Sporicidal agent	8% gas by weight
Hydrogen peroxide	Vapor phase sterilant, liquid sporicidal agent, antiseptic	4 µg per gram H₂O₂ vapor, 10%–25% solution, 3% solution
Peracetic acid	Liquid sterilant, vapor phase sterilant	0.2% Peracetic acid, 1 µg per gram peracetic acid
Quaternary ammonium compounds	General purpose disinfectant, antiseptic	Concentration dependent on application, Benzalkonium chloride

TABLE II

General Disinfectants (Bacteria, Yeasts, and Molds)^{^a}

Microbicidal Activity	Mode of Action
Alcohols (e.g., isopropyl and ethanol): Broad-spectrum antimicrobial against vegetative bacteria, mycobacteria, viruses and fungi	Alcohols owe their antimicrobial activity to their ability to denature cell proteins leading to a disruption of cellular function, and to a minor extent to their ability to cause membrane damage
Alkaline: Bactericidal and virucidal	Hydrolyzes and removes proteins, nucleic acids, endotoxins, and viruses
Acidic: Broad spectrum of bacteria	Attack lipid-rich cell walls

TABLE III

Sporicides (Spore-Forming Bacteria)^{^a}

Microbicidal Activity	Mode of Action
Accelerated Hydrogen Peroxide Technology: Bactericidal, virucidal, fungicidal, broad-spectrum sanitizing	Hydrogen Peroxide: Produces destructive hydroxyl free radicals that attack membrane lipids, DNA and other essential cell components
Peracetic acid, hydrogen peroxide, and acetic acid: Range of bacteria, molds, yeast and viruses (Registered uses: disinfectant, sterilant, sporicide, sanitizer, microbicide, virucide, fungicide, sporicidal disinfectant, antimicrobial solution, mold killing, one-step cleaner and disinfectant)	Hydrogen Peroxide: Produces destructive hydroxyl free radicals that attack membrane lipids, DNA and other essential cell components
	Peracetic Acid: Denatures proteins, disrupts cell wall permeability

TABLE IV

Hierarchy of Microbial Resistance to Disinfectants

Resistance to Disinfectants^{^a}
More Resistant	Microorganism	Examples	More Resistant
	Bacterial Spores	Bacillus cereus/Bacillus sphaericus
		Bacillus subtilis
		Clostridium spp.
	Mold Spores	Aspergillus, Penicillium
	Gram-negative bacteria	Pseudomonas, Providencia, Escherichia
	Vegetative Mold and Yeast	Aspergillus, Trichophyton, Candida
Less Resistant	Gram-positive bacteria	Staphylococcus, Streptococcus, Enterococcus	Less Resistant

TABLE V

Risk Assessment Scoring for Challenge Surface Selection

Risk Level	Description	Score
High	Surface characteristics: The surface has high surface roughness, susceptibility to surface degradation and/or water absorption, and presence of surface soil.	3
	Prevalence: The surface covers an important proportion of the facility surfaces and/or is often represented in different production areas (e.g., bulk or finishing).
	Operator interventions: During the process interventions, operators are in regular contact with the surface.
Medium	Surface characteristics: The surface properties do not facilitate microorganism development (low surface roughness, low level of degradation, low or no surface soil, etc.).	2
	Prevalence: The surface covers a moderate proportion of the facility surfaces or is limited to a specific area (e.g., bulk or finishing).
	Operator interventions: During the process interventions, operators are infrequently in contact with the surface.
Low	Surface characteristics: The surface properties prevent any microorganism development (bacteriostatic or bactericidal properties, very low roughness, very resistant and inert, typically clean surface prior to disinfection, etc.).	1
	Prevalence: The surface covers a small surface and/or is represented in only a few production rooms.
	Operator interventions: No process interventions with the surface.

TABLE VII

Typical Disinfectant Efficacy Challenge Organisms

Typical Disinfectant Efficacy Challenge Organisms^{^a}
Intended Use	AOAC Challenge Organisms	Typical Environmental Isolates
Bactericide	E. coli: ATCC 11229	M. luteus
	S. aureus: ATCC 6538	S. epidermidis
	P. aeruginosa: ATCC 15442	Corynebacterium jeikeium
	P. aeruginosa: ATCC 15442	P. vesicularis
Fungicide	C. albicans: ATCC 10231 or 2091	P. chrysogenum
	Penicillium chrysogenum: ATCC 11709	A. brasiliensis
	A. brasiliensis: ATCC 16404	A. brasiliensis
Sporicide	B. subtilis: ATCC 19659	B. sphaericus
Sporicide	B. subtilis: ATCC 19659	B. thuringiensis