sterilization disinfection by prof. dr. zainalabideen a abdulla, dtmh., mrcpi, ph.d., frcpath....
DESCRIPTION
Sterilization Destruction or elimination of all microbes including cells, spores, and viruses - Sterile = Devoid of microbial life - Physical or chemical methods in healthcare Dry heat Autoclaving (steam under pressure) Ethylene oxide gas Formaldehyde Radiation (UV, gamma rays)TRANSCRIPT
SterilizationSterilization&&
DisinfectionDisinfection
By
Prof. Dr. Zainalabideen A Abdulla, DTM&H., MRCPI, Ph.D., FRCPath. (U.K.)
LEARNING OBJECTIVES1 .Differentiate between sterilization, disinfection,
and sanitization2 .Differentiate between bactericidal and
bacteriostatic agents3 .Explain the process of pasteurization and
lyophilization4 .List several methods used to inhibit the growth
of microorganisms5 .Identify several factors that can influence the
effectiveness of disinfectants
Sterilization
Destruction or elimination of all microbes including cells, spores, and viruses
-Sterile = Devoid of microbial life
-Physical or chemical methods in healthcare • Dry heat
• Autoclaving (steam under pressure) • Ethylene oxide gas
• Formaldehyde • Radiation (UV, gamma rays)
DisinfectionThe elimination of most or all pathogens (except bacterial spores) from nonliving objects; using:
1 .Liquid chemicals (disinfectants) 2 .Wet pasteurization
Antiseptics: Disinfectants used on living tissues as the skin
Sanitization: Reduction of the microbial population to safe levels, e.g. in resturants
Microbicidal agents -Suffix: cide or cidal = “killing”
Examples : • Bactericidal = Kill bacteria
• Sporicidal = Kill bacterial spores • Viricidal = Kill viruses • Fungicidal = Kill fungi
• Pseudomonicidal= Kill Pseudomonas • Tuberculocidal = Kill M. tuberculosis
Pasteurization -A method to disinfect liquids (e.g. milk)
- Is not sterilization
- Not all microbes are killed
-63 Celsius 30 minutes
72 Celsius 15 seconds 140 Celsius 4 seconds
Microbistatic agents -Drugs or chemicals that inhibit reproduction
and metabolism of microorganisms (NOT necessarily kill them)
-Freeze drying & rapid freezing: Bacteriostatic
-Freeze drying = Lyophilization; preserve m.o.
Sepsis: Presence of pathogens in blood or tissues
Asepsis: Absence of pathogens -Medical or Surgical aseptic techniques, e.g.,
hand hygiene, sterile gloves, masks, and gowns
Antisepsis: Prevention of infection
Antiseptic technique: Use of antiseptics
Physical MethodsHeat
-The most common type of sterilization for inanimate objects able to with stand high temperatures
-Effect depends on: 1 .Temperature
2 .Time
-Pathogenic > susceptible than nonpathogenic
Thermal Death Point (TDP)Lowest temp. that kill all organism in a standardized pure culture within specified period
Thermal Death Time (TDT)The length of time to sterilize a pure culture at a specified temperature
Dry heat -160 – 165 Celsius 2 hours or
- 170 – 180 Celsius 1 hour - In oven
- Items: Metals, glassware, oils, waxes
Incineration: Burning; contaminated disposable materials; must NOT overloaded with protein and moist materials as feces, vomitus or pus
Flaming: Bunsen burner flame or electrical heat device for wires, loops or forceps
Moist heat 1. Boiling for 30 minutes, e.g. metal (needles),
glass. Not effective against spores, viruses and Mycobacterium.
2 .Autoclave (Moist heat + Pressure): - 15 psi + 121.5 Celsius for 20 minutes
- Kills spores, viruses, and vegetative form - Rubber can be autoclaved
- Indicators for completion: • Autoclave tape or • Solutions of bacterial spores
- Keep cans open, bottles covered loosely
Cold -Refrigeration: Slows metabolism & growth rate
-Slow freezing: Form crystals & rupture cells
-Rapid freezing (liquid nitrogen): Keep/Preserve
•Freeze- Thawing of food: Unsafe (spores vegetative forms
Desiccation -Dried clinical specimens and dust may contain
viable microorganisms.
Radiation - UV: • Sterilize vaccines, antisera, toxins
• May cause skin cancer, eye damage - X-ray, gamma and beta ray:
• Gamma ray sterilizes food as meat from Salmonella & Campylobacter
Ultrasonic Waves -For cleaning delicate equipment
- Tank of water + short US waves then sterilize
- In dental or medical clinics, e.g. glassware
Filtration -Different pore sizes; separate organisms
) bacteria, viruses, others (from liquid or gases
- Micro-pore filters
- High-Efficiency Particulate Air (HEPA) used in operating rooms, patient room to filter air
Gaseous Atmosphere -Aerobs/ Microaerophiles: Remove O2
-Anaerobic: Provide O2
• Hyperbaric Oxygen Chamber) increased pressure (to kill m.o.
Disinfectants (Chemical Agents) -Temporal or permanent
- Factors affecting disinfectants:
• Prior cleaning/proteinaceous materials • Organic matter load
• Bio-burden (microbial) • Concentration
• Time • Physical nature
• Temperature/ pH
cont./… Disinfectants -Susceptible: Vegetative state, fungi, protozoa,
most viruses
-Resistant: Mycobacteria, bacterial endospore, Pseudomonas spp., fungal spores,
hepatitis viruses
-Degree of resistance (see Table)
cont./… Disinfectants -Never use disinfectant if physical sterilization
is possible
-Do not destroy all bacteria & bacterial spores
-Spore/ Mycobacteria/Viruses destruction: • Formaldehyde / fumigation
• Ethylene oxide
Disinfectant characteristics •Broad
• Fast-acting • Not affected by organic materials
• Non-Toxic; Evaporation-Concentration • Leave residual anti-microbial film
• Soluble in water • Inexpensive
• Stable • Odorless
Antiseptics -Chemicals used safely on human tissues
such as skin
- Reduce numbers of organisms on surfaces
- Used at surgical incisions, at pores of folds of the skin
- Antiseptic soup + Brushing