Understanding the Scope and Impact of Hospital-Acquired Infections
According to estimates from the Centers for Disease Control and Prevention, healthcare-associated infections (HAIs) kill more people each year globally than car accidents, breast cancer or Aids, and cost the US healthcare system an estimated $30bn-$45bn each year. HAIs can develop more than 48-72 hours after patient admission and up to ten days after hospital discharge, and hospitals, community clinics, nursing homes and centres handling outpatient surgery, dialysis and rehabilitation are all possible breeding grounds for multiple drug-resistant microbes. The most common HAIs are:
- central line-associated bloodstream infections
- methicillin-resistant Staphyloccocus aureus (MRSA)
- vancomycin-resistant Enterococci bloodstream infections
- Clostridium difficile
- surgical site infections (SSIs).
While government initiatives such as awareness programmes and discharge surveys are helpful in combating HAIs, in the US, the Department of Health and Human Services announced the Partnership for Patients initiative to reduce HAIs. It focuses on serious HAIs such as catheter-associated urinary tract infections, bloodstream infections, SSIs and ventilator-associated pneumonia.
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Along with such initiatives and strong reporting systems like the National Nosocomial Infections Surveillance System and National Hospital Discharge Survey, it is also mandatory for US healthcare settings to improve the standards of sterilisation and disinfection in their facilities. Chemical sterilants and disinfectants are the most important defence against HAIs. Prevention strategies may range from hand hygiene using antiseptics and low-level disinfectants to the sterilisation of gastro-intestinal endoscopes using potent, high-level disinfectants. Even environmental cleanliness with phenols and bleach solutions may help prevent fatal HAIs such as Clostridium difficile.
To help healthcare facilities decide on the disinfectants and disinfection procedures that best fit their needs, GlobalData has profiled the top ten disinfection solutions.
Sterilants and high-level disinfectants
1 Formaldehyde
Formaldehyde – primarily available as a water-based solution called formalin, which contains 37% formaldehyde by weight – is used as a high-level disinfectant and sterilant. Formaldehyde exerts its bactericidal, tuberculocidal, fungicidal, virucidal and sporicidal effects in the aqueous state, as well as in combination with low-temperature steam.
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By GlobalDataThis extremely reactive chemical’s mechanism of action is attributed to its interactive and cross-linking properties with protein, DNA and RNA in vitro, resulting in the disruption of DNA synthesis. It can also penetrate bacterial spores.
Formaldehyde has been traditionally used to sterilise equipment such as surgical instruments and haemodialysers in combination with alcohols. Paraformaldehyde, a solid polymer of formaldehyde, is used in combination with low-temperature steam for the disinfection of heat-sensitive medical equipment.
Exposure hazards and the potential carcinogenic effects of formaldehyde have limited its healthcare uses recently, while next-generation aldehydes such as glutaraldehyde and o-phthalaldehyde, with better sporicidal activity, faster onset of action and lesser exposure effects, have replaced formaldehyde in the disinfection manuals of most healthcare establishments.
2 Glutaraldehyde
Glutaraldehyde is a saturated dialdehyde widely used as a potent sterilant and high-level disinfectant. Its broad spectrum, covering bactericidal, sporicidal, fungicidal and virucidal activity, makes it an ideal chemical for the low-temperature disinfection and sterilisation of critical and semi-critical equipment such as endoscopes, dialysers and surgical tools.
Aqueous solutions of glutaraldehyde when activated (rendered alkaline at 7.5- 8.5pH) become sporicidal, while its microbicidal action is attributed primarily to its strong association with the outer layers of bacterial cells and the alkylation of sulphydryl, hydroxyl, carboxyl and amino groups, which alter RNA, DNA and protein synthesis within microorganisms.
Glutaraldehyde is also mycobactericidal, and glutaraldehyde formulations with phenols (Sporicidin from Sporicidin International) and alcohols (Aldahol III from Healthpoint) have better usage life, while maintaining excellent microbicidal activity. Glutaraldehyde exposure should be monitored to ensure a safe working environment. Acute or chronic exposure, resulting in skin irritation, mucous membrane irritation and multiple pulmonary symptoms such as occupational asthma and allergic rhinitis have been reported in healthcare workers.
Due to its exposure hazards, US healthcare associations advocate the use of glutaraldehyde alternatives such as o-phthalaldehyde, hydrogen peroxide and peracetic acid.
3 Ortho-phthalaldehyde
Since its introduction in 1999, ortho-phthalaldehyde (OPA) has been accepted as a better, safer alternative to glutaraldehyde in most US healthcare facilities. Cidex OPA by Advanced Sterilization Products (a Johnson & Johnson company) was cleared by the US FDA as a high-level disinfectant and emerged as a suitable replacement of glutaraldehyde for the disinfection of endoscopes.
OPA has excellent microbiocidal activity and superior mycobactericidal activity compared with glutaraldehyde, and has potent bactericidal and sporicidal activity. Like glutaraldehyde, it interacts with amino acids, proteins and microorganisms.
OPA has many advantages over glutaraldehyde, such as improved stability at varying pH ranges, lower inhalation exposure risk and a wider range of material compatibility, although it costs almost three times more; but, considering the cost of the sophisticated ventilation systems needed to minimise the respiratory hazards of using glutaraldehyde, OPA is more economical.
4 Hydrogen peroxide
Disinfectant solutions containing 7.5% hydrogen peroxide have been approved by the US FDA for sterilisation and high-level disinfection in healthcare settings.
Its good, broad-spectrum bactericidal, virucidal, sporicidal and fungicidal properties, combined with its excellent stability and environmentally friendly characteristics, have made hydrogen peroxide the disinfectant of choice for semi-critical and non-critical equipment while being an ideal surface disinfectant.
Despite not being listed as equipment-compatible by all endoscope manufacturers, hydrogen peroxide-based disinfectant solutions are still considered ideal alternatives for other toxic sterilants, such as ethylene oxide and aldehyde disinfectants. Hydrogen peroxide produces destructive hydroxyl-free radicals that act on membrane lipids, DNA and other essential cell components.
FDA-cleared hydrogen peroxide-based disinfectants include Sporox Sterilizing & Disinfection Solution (Sultan Chemists) and Resert XL HLD High Level Disinfectant (Steris).
5 Peracetic acid
Another emerging alternative to ethylene oxide and aldehyde sterilants is peracetic acid. Peracetic acidbased solutions are considered to be a more potent disinfectant than hydrogen peroxide; are sporicidal, bactericidal, virucidal and fungicidal at low concentrations; and are environment friendly. They have replaced traditional disinfectants for medical devices, endoscopes and haemodialysers.
It also acts as an environmental surface sterilant, and behaves similarly to other oxidising agents, disrupting cell wall permeability and oxidising sulphhydryl and sulphur bonds in proteins, enzymes and other metabolites.
The FDA has cleared Steris 20 Sterilant (Steris) for use with Steris System 1, an automated liquid chemical sterilisation processor for endoscopes, arthroscopes and other surgical instruments.
6 Hydrogen peroxide/peracetic acid combination
Peracetic acid, when combined with hydrogen peroxide, was found to be more effective, typically against glutaraldehyde-resistant mycobacteria. Combination products cleared by the FDA include Acecide High Level Disinfectant and Sterilant (Minntech), EndoSpor Plus Sterilizing and Disinfecting Solution (Cottrell) and Peract 20 Liquid Sterilant/ Disinfectant (Minntech).
The combination of peracetic acid and hydrogen peroxide has been used for disinfecting haemodialysers, but the mix was found to be incompatible with flexible gastrointestinal endoscopes as claimed by leading US manufacturers.
Intermediate-level disinfectants
7 Sodium hypochlorite
Chlorine-releasing agents (CRAs), the most popular sodium hypochlorite solution, are widely used for the disinfection of hard surfaces and blood spillages containing the human immunodeficiency virus or hepatitis B virus.
Recently, sodium hypochlorite was designated as the best defence against hospital-acquired and community-acquired Clostridium difficile infections. With a broad spectrum of antimicrobial activity, sodium hypochlorite is inexpensive with low toxicity.
CRAs are highly active oxidising agents and destroy the cellular activity of proteins. Hypochlorous acid, the active moiety, has been shown to have harmful effects on bacterial DNA through the formation of chlorinated derivatives of nucleotide bases.
High concentrations of sodium hypochlorite display significant levels of sporicidal and virucidal activity. The most popular sodium hypochlorite products in the US are Clorox Germicidal Wipes and Dispatch Hospital Cleaner Disinfectant with Bleach (The Clorox Company), and Sterilox High Level Disinfectant System (Sterilox Technologies).
8 Iodophors
Iodophors, complexes of iodine and a solubilising agent or carrier, are used as antiseptics and surface disinfectants. Iodine has bactericidal, fungicidal, tuberculocidal, virucidal and sporicidal properties, while its antiseptic properties are well known.
Iodophors, such as povidone-iodine and poloxamer-iodine, are much more stable, have fewer irritant characteristics and exert better microbicidal action than aqueous iodine solutions. The FDA has not cleared any liquid chemical sterilant or high-level disinfectant with iodophors as the main active ingredient, but iodophors are still used in healthcare settings for disinfecting blood culture bottles and medical equipment such as thermometers.
Low-level disinfectants
9 Phenols
Since Dr Joseph Lister’s use of phenols for his pioneering work on antiseptic surgery, phenolic disinfectants have been used as low and intermediate-level disinfectants. Phenolic disinfectants are effective bactericides, fungicides, tuberculocides and virucides, but are ineffective against spore-forming bacteria such as Clostridium difficile.
EPA-registered phenolic disinfectants are used to disinfect surface areas and non-critical medical devices. Phenolics are not FDA-cleared as high-level disinfectants for use with semi-critical items.
Phenolic disinfectants disrupt the cell membrane of microorganisms, and two phenol derivatives used commonly in hospital disinfectants are orthophenylphenol (Amphyl, Reckitt Benckiser) and ortho-benzyl-parachlorophenol (Clorox Disinfectant Cleaner, The Clorox Company).
10 Quaternary ammonium compounds
Quaternary ammonium compounds (QACs) are used for a variety of clinical purposes such as preoperative disinfection, disinfection of non-critical instruments, and hard-surface cleaning and deodorisation.
QACs possess bactericidal, fungicidal and virucidal properties; however, they only display mycobacteriostatic and sporostatic activity. Quaternary ammonium disinfectants contain NH4+, the strong positive charge that results in better contact with negatively charged surfaces, making them good cleaning agents.
EPA-registered QACs are appropriate for use in disinfecting medical equipment that contacts unbroken skin, such as blood pressure cuffs. US hospitals also use quaternary ammoniumbased disinfectants for the terminal disinfection of hospital rooms.
