Disinfection Sterilization and Antisepsis References and Recommended Further

Disinfection, Sterilization and Antisepsis

References and Recommended Further Readings 1. Medical Microbiology, 6 th Ed. Murray P. R. , Rosenthal K. S. , Pfaller M. A. 2009, Mosby. 2. Mim’s Medical Microbiology, 4 th Ed. Goering R. V. , et al. 2008, Mosby. 3. Sherris Medical Microbiology, 5 th Ed. Ryan K. J. , et al. 2010, Mc. Graw Hill. 4. Manual of Clinical Microbiology, 9 th Ed. Murray P. R. , et al. 2007, ASM Press.

Purpose and definitions of Antisepsis, Disinfection and Sterilization • A strategy to control infections: Antisepsis, disinfection and sterilization are among the strategies to control the presence of microorganisms. Antisepsis, disinfection and sterilization are basic components of any infection control program.

Definitions of Sterilization, Disinfection, Decontamination, and Antisepsis

Definitions of germicide, sterilant (chemical-), high-level disinfectant, intermediate-level disinfectant, lowlevel disinfectant, minimum effective concentration, cleaning (or precleaning)

Microorganisms’ resistance to disinfectants

Classification of medical devices

Spaulding classification of clinical (medical) devices

Methods of Sterilization • Sterilization; – can be achieved by employing different methods and techniques.

Sterilization • • Sterilization is the destruction of all microbes, including the more resilient forms such as bacterial spores, mycobacteria, non-enveloped (non-lipid) viruses, and fungi. – can be done by using physical, gas vapor, or chemical sterilants. – selected for their safety and efficacy Physical sterilants; – Moist – Dry heat • most common sterilizing methods used in hospitals • indicated for most materials • exceptions are; – heat sensitive materials or – toxic or volatile chemicals – Filtration • useful for removing bacteria and fungi from; – air (with high-efficiency particulate air [HEPA] filters) or – solutions • unable to remove viruses and some small bacteria – Ultraviolet or ionizing radiation (e. g. , microwave or gamma rays) • also common • limitation of U. V. radiation is that direct exposure is required

Sterilization • Gas vapor sterilants; – Ethylene oxide • most commonly used • highly efficient • strict regulations limit its use; flammable, explosive, and carcinogenic to lab animals – Formaldehyde • limited because carcinogenic • restricted primarily to sterilization of HEPA filters – Hydrogen peroxide • effective because of the oxidizing nature of the gas • used for the sterilization of instruments – Plasma gas sterilization • A variation of sterilization with hydrogen peroxide » hydrogen peroxide is vaporized, and » then reactive free radicals are produced with either microwavefrequency or radio-frequency energy • efficient sterilizing method • does not produce toxic byproducts • will replace many of the applications for ethylene oxide • cannot be used with materials that absorb hydrogen peroxide or react with it

Sterilization • Chemical sterilants; – Peracetic acid • oxidizing agent • excellent activity • end products (i. e. , acetic acid and oxygen) are nontoxic – Glutaraldehyde • safety is a concern – care must be used when handling this chemical

Disinfection Methods of disinfection • Microbes are also destroyed by disinfection procedures, but more resilient organisms can survive. • Disinfection procedures categorized as; – high level, – intermediate level, and – low level.

Levels of Disinfection • • High-level disinfection; – can approach sterilization in effectiveness Intermediate-level disinfection; – spore forms can survive Low-level disinfection; – many microbes can remain viable However; classification of disinfectants by their level of activity is misleading – because: • effectiveness of these procedures is influenced by; – the nature of the item to be disinfected, – number and resilience of the contaminating organisms, – amount of organic material present (which can inactivate the disinfectant), – type and concentration of disinfectant, and – duration and temperature of exposure

Levels of Disinfection • High-level disinfectants; – used for items involved with invasive procedures (critical devices) that cannot withstand sterilization procedures • certain types of endoscopes, • surgical instruments with plastic or other components that cannot be autoclaved – disinfection of these and other items is most effective if; » cleaning the surface to remove organic matter precedes treatment – examples; • moist heat, and • liquids – glutaraldehyde, – hydrogen peroxide, – peracetic acid, – chlorine compounds

Levels of Disinfection • Intermediate-level disinfectants; – used to clean surfaces or instruments in which; • contamination with bacterial spores and other highly resilient organisms is unlikely – semicritical instruments and devices » flexible fiberoptic endoscopes, » laryngoscopes, » vaginal specula, » anesthesia breathing circuits » other items – examples; • alcohols, • iodophor compounds, • phenolic compounds

Disinfection • • Low-level disinfectants; used to treat noncritical instruments and devices; – blood pressure cuffs, – electrocardiogram electrodes, – stethoscopes, and other items • these items come into contact with patients, but they do not penetrate through mucosal surfaces or into sterile tissues • example; – quaternary ammonium compounds • The level of disinfectants used for environmental surfaces; – is determined by the relative risk these surfaces pose as a reservoir for pathogenic organisms • to clean the surface of instruments contaminated with blood; – a higher level of disinfectant • to clean surfaces that are "dirty, " such as floors, sinks, and countertops; – a lower level of disinfectant – exception to this rule is: • a particular surface that is implicated in a nosocomial infection; – a bathroom contaminated with Clostridium difficile (spore-forming anaerobic bacterium) or – a sink contaminated with Pseudomonas aeruginosa , etc. • a disinfectant with appropriate activity against the implicated pathogen should be selected

Antisepsis • Antiseptic agents; – used to reduce the number of microbes on skin surfaces

Germicidal and other properties of disinfectants and antiseptics

Overview of disinfectants

Overview of antiseptics

Antisepsis – Alcohols; • excellent activity against all groups of organisms – except spores • nontoxic – tend to dry the skin surface because they remove lipids • do not have residual activity • inactivated by organic matter ; – surface of the skin should be cleaned before alcohol is applied – Iodophors; • excellent skin antiseptic agents – having a range of activity similar to that of alcohols • slightly more toxic to the skin • limited residual activity • inactivated by organic matter • Iodophors and iodine preparations are frequently used with alcohols for disinfecting the skin surface – Chlorhexidine; • broad antimicrobial activity – kills organisms at a much slower rate than alcohol • activity persists – although organic material and high p. H levels decrease its effectiveness – – parachlorometaxylenol (PCMX); • is limited primarily to gram-positive bacteria • nontoxic and has residual activity – used in handwashing products Triclosan; • active against bacteria but not against many other organisms • a common antiseptic agent in deodorant soaps and some toothpaste products