Antimicrobial biocides in the healthcare environment: efficacy, usage, policies, and perceived problems

Figures & data

Table 1 Treatment of the hospital environment and equipment

Environment/Equipment	Comments	Treatment
Walls, ceiling	Rarely heavily contaminated (surfaces need to remain dry)	Occasional cleaning and drying. Chemical disinfection
	Occasional spillages
Floorsa	More heavily contaminated; only a small proportion are potential pathogens. Related to the activity on the ward (eg, number of people)	Cleaning with detergents. Disinfection recommended only in high-risk areas
Baths	Many bacteria remain on the surface after emptying the bath	Thorough cleaning with detergents. Disinfection necessary in maternity and surgical units where multiresistant bacteria might be present
Washbowls	High number of bacteria can grow if not dried properly	Thorough cleaning and drying
Toilets	Potential risk during gastrointestinal infection	Thorough cleaning with detergents, except during infection outbreaks for which chemical disinfection might be indicated
Bedpans and urinals	Potential risk during gastrointestinal infection	Thermal disinfection recommended
Crockery and cutlery	Heavily contaminated after handwash processing	Washing in a machine with minimal temperature of 50–60°C recommended
Cleaning equipment	Floor mops heavily contaminated	Heat disinfection recommended. Immersion in chemical disinfectants should be avoided
Babies' incubator	Rarely heavily contaminated but high risk of transmission	Thorough cleaning and drying of surfaces. Chemical disinfection might be considered
Respiratory ventilators	Accumulation of moisture associated with bacterial growth	Changing reservoir bag, tubing and connectors every 48 hours. Heat disinfection for respiratory circuits recommended. Use of heat-moisture exchangers or filters recommended. Use of washer–disinfectors for reusable circuits
Anesthetic equipment	Machines rarely heavily contaminated providing that the associated tubing is regularly changed	Low temperature steam or washing-machine (70–80°C) for corrugated tubing. Single use circuit preferred in some cases. Chemical disinfection to be avoided
Endoscopes	May be heavily contaminated	High-level disinfection for flexible heat sensitive endoscopes. Heat or gaseous sterilization for rigid devices
Vaginal specula and other vaginal devices	Potential risk of acquiring viral infection	Single use items are preferred. Heat sterilization recommended
Tonometers	Potentially risk of viral transmission	Chemical disinfection requiredb
Stethoscopes	Some reports of staphylococci transmission	Thorough regular cleaning with 70% alcohol recommended
Sphygmomanometer	Some reports of staphylococci transmission	Thorough washing and drying of contaminated cuff.
Linen	May be heavily contaminated	Heat (65°C) for heat-stable linen. Chemical disinfection in penultimate rinse, laundering at 40°C and dry at 60°C for heat-sensitive linen
Dressing trolleys, mattress covers, supports, curtains	May require decontamination	Thorough cleaning necessary. Decontamination by heat preferable to chemical disinfection

a Carpets may add additional problems (Fraise 2004b)

b In case of potential transmission of spongiform encephalopathy, disposable tonometer head should be used.

NOTE: Table compiled from information from Ayliffe 1993; Rutala 1990, ²⁰⁰⁰; Rutala and Weber 1999, 2004b; Fraise 1999, ²⁰⁰⁴; Nelson 2003.

Table 2 Principles of disinfection policies

Objectives and purposes	To prevent infection but in practical terms to reduce the bioburden to a level at which infection is unlikely. Need to consider the standard of hygiene expected by patients and staff
Categories of risk for patients and treatment of equipment and environment
High risk	Sterilization by heat or other methods (eg, ethylene oxide; low temperature steam formaldehyde); high-level disinfection may be acceptable (eg, GTA, OPA, PAA)
Intermediate risk	Disinfection
Low risk	Cleaning and drying usually sufficient; disinfection
Minimal risk	Cleaning and drying; disinfection in case of contaminated spillage
Requirements of chemical disinfectants
Spectrum of activity	“cidal” rather than “static” activity
Efficacy	Rapid action, notably on surfaces
Incompatibility	should not be neutralized/quenched easily, eg, by hard water, soap, organic load
Toxicity	Should be minimal
Damages to products/surfaces Costs	Corrosiveness should be minimal, especially at in use dilution. Should not damage the surface/articles to be disinfected, eg, endoscopes should be acceptable and supplies assured
Implementations of the disinfection policies
Organization	Infection control team should be responsible. Need clear cut and well defined responsibilities
Training	End users (nursing and domestic staff) should be trained appropriately. Clear schedules and supervision by trained staff should be in place.
Distribution and dilution	Staff training is essential. Suitable dispensers of disinfectants should be available
Testing of disinfectants	Need to be properly documented and assessed preferably by an independent organisation following standard protocols.
Costs	Should be considered carefully

Abbreviations: GTA, glutaraldehyde; OPA, ortho-phthalaldehyde; PAA, peracetic acid.

Table 3 Factors influencing the antimicrobial activity of biocides

Factorsa	Comments	Relevance and consequence in practice
Factors inherent to the biocide
Concentration	Understand the concentration exponent (ie, the effect of dilution upon activity)	Appropriate staff training required
Contact time	Longer contact time often associated with increased activity	Appropriate staff training required
Organic load	Quench the activity of a biocide or protect microorganisms	Combination of physical (cleaning) and chemical action required
Formulation	Possible inactivation of biocide	Understand the nature of the active agent
Temperature	Important for some devices (eg, endoscope washer)	Important to understand that adequate staff training is required with certain types of equipment
pH	Affect both the biocide (stability and ionisation) and the microorganism (growth and electric charge)	Probably not as important in the healthcare environment
Factors inherent to the cell
Presence of biofilm	Dormant “persister” cells difficult to eradicate. Likely to be present on equipment, certain surfaces	Combination of physical (cleaning) and chemical action required
Type of microorganisms	Will affect the choice of the agent to use. Bacterial spores: the most resistant; envelope viruses: the least resistant	Evaluation of the possible type of biocide needed
Number of microorganisms	High number more difficult to eradicate	Biocides often used in high (ie, excess) concentration. High number of cells might not be a problem

a Factors listed in order of importance.

Table 4 Mechanisms conferring biocide resistance in bacteria

Mechanism	Effect	Example of structures (and microorganisms)
Decrease in biocide concentration
Impermeability barrier	Decrease the amount of a biocide that penetrates in the cell	Spore coats (bacterial spores), LPS (Gram-negative bacteria), mycoylarabinogalactan layer (mycobacteria)
Multidrug efflux pumps	Decrease the amount of a biocide within the cell	QacA-D, QacG and QacH, Nor A (Staphylococcus aureus), MexAB-OprM, MexCD-OprJ, MexEF-OprN, MexJK, QacE, QacΔ1 (Pseudomonas aeruginosa), QacE, SilABC (Klebsiella pneumoniae), AcrAB-TolC, AcrEF-TolC, EmrE (Escherichia coli)
Degradation	Inactivate a biocide outside or within a cell	Hydrolase and reductase (E. coli; S. aureus), aldehyde dehydrogenase (E. coli, P. aeruginosa), catalases, superoxide dismutase and alkyl hydroxyperoxidasesa (E. coli)
Alteration of target(s) and metabolism
Modification of target	Render the effect of a biocide ineffectiveb	Enoyl-acyl carrier reductase (S. aureus; E. coli; Mycobacterium smegmatis).
Multiplication of targets	Decreases the effective concentration of a biocide	Interaction with bacterial glycocalyx (in biofilm)
Alteration of metabolism	Decrease the detrimental effect of a biocide	Phenotypic alteration and “persisters” (bacterial biofilm)

a Reduction of free radicals within the cell (eg, following exposure to an oxidising agent);

b Has only been observed with the bisphenol triclosan.

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