Microbial Control Methods Quiz
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What is the primary mechanism by which moist heat sterilization kills microorganisms?

  • By coagulating their proteins (correct)
  • By breaking down their cell walls
  • By evaporating their moisture content
  • By disrupting their DNA structure

    • At what temperature is pasteurization typically conducted in the holder method?

  • 100°C for 5 minutes
  • 56°C for 1 hour
  • 72°C for 15 seconds
  • 63°C for 30 minutes (correct)

    • What is the purpose of the special vaccine bath at 60°C?

  • To boil culture media for microbiological studies
  • To inactivate non-sporing bacteria in vaccine preparation (correct)
  • To sterilize water for laboratory use
  • To preserve serum for long-term storage

    • Which type of microorganism can survive boiling for up to 20 hours or more?

    <p>Endospores</p> Signup and view all the answers

    Who invented the autoclave, which works on the principle of steam under pressure?

    <p>Charles Chamberland</p> Signup and view all the answers

    What is the primary mechanism by which hydrogen peroxide inhibits enzymatic activity?

    <p>Attacking sulfhydryl groups</p> Signup and view all the answers

    Which microorganisms is ethylene oxide effective against?

    <p>All types of microorganisms including viruses and spores</p> Signup and view all the answers

    What is the characteristic action of metallic salts used as disinfectants?

    <p>Coagulating proteins</p> Signup and view all the answers

    Which type of filter is commonly used to sterilize heat-labile liquids?

    <p>All of the above</p> Signup and view all the answers

    Which of the following is a characteristic of non-ionizing radiation?

    <p>Absorbed as heat</p> Signup and view all the answers

    What is the purpose of sterilization?

    <p>To destroy all viable microorganisms</p> Signup and view all the answers

    Which of the following describes a bacteriostatic agent?

    <p>An agent that inhibits the growth of bacteria</p> Signup and view all the answers

    What distinguishes antiseptics from disinfectants?

    <p>Antiseptics can be used on skin surfaces</p> Signup and view all the answers

    Which term describes the absence of significant contamination?

    <p>Asepsis</p> Signup and view all the answers

    What is the main aim of asepsis in a medical setting?

    <p>To eliminate contaminants before surgery</p> Signup and view all the answers

    What process is specifically designed to destroy vegetative pathogens?

    <p>Disinfection</p> Signup and view all the answers

    Which option is an example of degermation?

    <p>Scrubbing skin before surgery</p> Signup and view all the answers

    Which statement is true about sporicidal agents?

    <p>They kill bacterial spores effectively</p> Signup and view all the answers

    What is the primary method of sterilization using dry heat?

    <p>Dry Oven</p> Signup and view all the answers

    What is the duration for sterilization at 121ºC?

    <p>15 minutes</p> Signup and view all the answers

    Which of the following is NOT a type of physical agent used for microbial control?

    <p>Chemical Agents</p> Signup and view all the answers

    At what temperature range does dry heat sterilization typically operate?

    <p>50oC to 250/300oC</p> Signup and view all the answers

    What is one of the principles of effective disinfection?

    <p>Concentration of disinfectant</p> Signup and view all the answers

    Which chemical agent is known to have a lethal effect on viruses?

    <p>Formaldehyde</p> Signup and view all the answers

    Which method is employed to destroy contaminated materials using high temperatures?

    <p>Flaming/Incineration</p> Signup and view all the answers

    How long is it desirable to maintain a holding period at 160oC for dry heat sterilization?

    <p>2 hours</p> Signup and view all the answers

    What concentration of alcohol is recommended for disinfection?

    <p>60-90%</p> Signup and view all the answers

    What is the primary use of glutaraldehyde?

    <p>To treat rubber anesthetic tubes</p> Signup and view all the answers

    Which of the following articles is suitable for sterilization by dry heat?

    <p>Metal instruments</p> Signup and view all the answers

    What is a property of iodine as a disinfectant?

    <p>Actively bactericidal with moderate action against spores</p> Signup and view all the answers

    Which category of mechanical removal methods involves using a membrane to separate microbes from liquids?

    <p>Filtration</p> Signup and view all the answers

    What is the purpose of double-walled insulation in a dry heat sterilizer?

    <p>To keep the heat inside and conserve energy</p> Signup and view all the answers

    What substance is known to limit the effectiveness of hydrogen peroxide?

    <p>Catalase</p> Signup and view all the answers

    Which disinfectant is derived from coal tar?

    <p>Phenols</p> Signup and view all the answers

    What does sterilization primarily aim to achieve?

    <p>Eliminate all microorganisms including spores</p> Signup and view all the answers

    What is a common method of sterilization?

    <p>Autoclaving at 121°C</p> Signup and view all the answers

    What is the main difference between disinfection and sterilization?

    <p>Sterilization kills all microorganisms while disinfection does not</p> Signup and view all the answers

    Which of the following is NOT a method of sterilization?

    <p>Use of boiling water</p> Signup and view all the answers

    What role does damage to nucleic acids play in microbial control?

    <p>It can lead to cell death and inhibit replication</p> Signup and view all the answers

    What factor contributed to the high mortality rate from nosocomial infections in the mid 1800s?

    <p>Lack of aseptic techniques in surgeries</p> Signup and view all the answers

    Which method might be used to sterilize intravenous solutions?

    <p>Filtration</p> Signup and view all the answers

    What type of microorganisms does disinfection specifically target?

    <p>Primarily pathogens but not all organisms</p> Signup and view all the answers

    What is the most reliable method for sterilization?

    <p>Autoclaving</p> Signup and view all the answers

    Which chemical agent is most commonly used for skin antisepsis before surgery?

    <p>Alcohol</p> Signup and view all the answers

    What is the temperature and time used for standard autoclaving?

    <p>121°C for 15-20 minutes</p> Signup and view all the answers

    Which of the following methods is NOT considered sterilization?

    <p>Pasteurization</p> Signup and view all the answers

    What does a bacteriostatic agent do?

    <p>Inhibits bacterial growth</p> Signup and view all the answers

    Which microbial structure is the most resistant to sterilization methods?

    <p>prions</p> Signup and view all the answers

    Which term refers to reducing microbial load on living tissue?

    <p>Antisepsis</p> Signup and view all the answers

    What is the primary aim of aseptic techniques?

    <p>Prevent microbial contamination</p> Signup and view all the answers

    Which agent is classified as a sporicidal?

    <p>Hydrogen Peroxide</p> Signup and view all the answers

    What pressure is applied in a standard autoclave cycle?

    <p>15</p> Signup and view all the answers

    Which of the following is an example of dry heat sterilization?

    <p>Hot air oven</p> Signup and view all the answers

    Which of the following uses ionizing radiation for sterilization?

    <p>Gamma rays</p> Signup and view all the answers

    What is the primary purpose of pasteurization?

    <p>Reduce microbial loads in liquids</p> Signup and view all the answers

    How long is milk heated for both the Holder Method and Flash Process?

    <p>63C for 30 MIN/ 72C for 15-20 SEC</p> Signup and view all the answers

    Which chemical is used for sterilizing heat-sensitive medical instruments?

    <p>Ethylene oxide</p> Signup and view all the answers

    What is the difference between sterilization and disinfection?

    <p>Sterilization kills all microorganisms, disinfection reduces microbial load.</p> Signup and view all the answers

    What term describes mechanical removal of microbes from skin?

    <p>Degermation</p> Signup and view all the answers

    Study Notes

    Sterilization, Disinfection, and Antisepsis

    • Microorganisms are the agents of contamination, infection, and decay
    • Early civilizations practiced methods like salting, smoking, pickling, and sunlight exposure to remove microorganisms
    • In the mid-1800s, Lister developed aseptic techniques to prevent contamination of surgical wounds
    • Prior to this, nosocomial infections caused death in 10% of surgeries and up to 25% of mothers delivering in hospitals died due to infections
    • Methods for controlling microbial growth include altering membrane permeability, damaging proteins, and damaging nucleic acids

    Learning Outcomes

    • Students should be able to define sterilization, disinfection, and antisepsis
    • Students should understand methods of sterilization and disinfection (physical, chemical, and mechanical removal)
    • Students should be able to explain the role of sterilization and disinfection in disease control

    Introduction

    • Microorganisms are the agents of contamination, infection, and decay
    • Hence it's necessary to remove them from materials and areas
    • Early civilizations practiced salting, smoking, pickling, and exposure to sunlight

    Aseptic Techniques

    • In the mid-1800s, Lister developed aseptic techniques to prevent contamination of surgical wounds
    • Prior to this, nosocomial infections caused death in 10% of surgeries
    • Up to 25% of mothers delivering in hospitals died due to infection

    Methods of Microbial Growth Control

    • Alteration of membrane permeability
    • Damage to proteins
    • Damage to nucleic acids
    • Order of resistance (most to least): Prions, Endospores of bacteria, Mycobacteria, Cysts of protozoa, Vegetative protozoa, Gram-negative bacteria, Fungi, Viruses without envelopes, Gram-positive bacteria, Viruses with lipid envelopes

    Definition of Sterilization

    • The process of freeing an article from microorganisms, including their spores

    Sterilization

    • Sterilization is the killing or removal of all microorganisms, including bacterial spores, which are highly resistant.
    • Sterilization is usually carried out by autoclaving, which consists of exposure to steam at 121°C under a pressure of 15 lb/in² for 15 minutes.
    • Surgical instruments that can be damaged by moist heat are usually sterilized by exposure to ethylene oxide gas, and most intravenous solutions are sterilized by filtration.

    Methods of Sterilization

    • Table 3-1 (Physical Sterilants): Steam under pressure (121°C or 132°C for various time intervals), Filtration (0.22- to 0.45-μm pore size; HEPA filters), UV radiation (variable exposure to 254-nm wavelength), Ionizing radiation (variable exposure to microwave or gamma radiation)
    • Table 3-1 (Gas Vapor Sterilants): Ethylene oxide (450-1200 mg/L at 29°C to 65°C for 2-5 hr), Hydrogen peroxide vapor (30% at 55°C to 60°C), Plasma gas (Highly ionized hydrogen peroxide gas)
    • Table 3-1 (Chemical Sterilants): Peracetic acid (0.2%), Glutaraldehyde (2%)

    Disinfection

    • Disinfection is the killing of many, but not all, microorganisms
    • For adequate disinfection, pathogens must be killed, but some organisms and bacterial spores may survive
    • Disinfectants: corrosive phenol-containing
    • Antiseptics: less toxic materials (such as ethanol and iodine) used on skin surfaces

    Methods of Disinfection

    • Table 3-2 (Heat): Moist heat (75°C to 100°C for 30 min)
    • Table 3-2 (Liquid): Glutaraldehyde (2%-3.2%), Hydrogen peroxide (3%-25%), Chlorine compounds (100-1000 ppm of free chlorine), Alcohol (70%-95%), Phenolic compounds (0.4%-5.0%), lodophor compounds (30-50 ppm of free iodine/L), Quaternary ammonium compounds (0.4%-1.6%)

    Don't Forget

    • Sterilization: Destroys all viable microbes, including viruses and endospores
    • Disinfection: Destroys vegetative pathogens, not endospores; for inanimate objects
    • Antiseptic: Disinfectants applied directly to exposed body surfaces
    • Sanitization: Any cleansing technique that mechanically removes microbes

    Antiseptic Agents

    • Table 3-3: Alcohol (70%-90%), lodophors (1-2 mg of free iodine/L; 1%-2% available iodine), Chlorhexidine (0.5%-4.0%), Parachlorometaxylenol (0.50%-3.75%), Triclosan (0.3%-2.0%)

    Terminology

    • Degermation: Mechanically removing microbes
    • Sepsis: Bacterial contamination
    • Asepsis: Absence of significant contamination
    • Bactericidal (microbicidal): Kills microbes
    • Bacteriostatic (microbiostatic): Inhibits growth and multiplication

    Terminology (continued)

    • Bacteriostatic Agent: inhibits bacteria growth but does not necessarily kill them.
    • Bactericide: kills bacteria, most do not kill endospores.
    • Sporicidal: kills spores.
    • High, intermediate, and low-level agents are different levels of germicides.

    Box 3-1 Definitions

    • Antisepsis (Use of chemical agents on the skin or other living tissue to inhibit or eliminate microbes; no sporicidal action is implied)
    • Disinfection (Use of physical procedures or chemical agents to destroy most microbial forms; bacterial spores and other relatively resistant organisms may remain viable; disinfectants are sub-divided into high-, intermediate-, and low-level agents)
    • Germicide (Chemical agent capable of killing microbes; includes virucide, bactericide, sporicide, tuberculocide, and fungicide)
    • High-level disinfectant (A germicide that kills all microbial pathogens except large numbers of bacterial spores)
    • Intermediate-level disinfectant (A germicide that kills all microbial pathogens except bacterial endospores)
    • Low-level disinfectant (A germicide that kills most vegetative bacteria and lipid-enveloped and medium-size viruses)
    • Sterilization (Use of physical procedures or chemical agents to destroy all microbial forms, including bacterial spores) Order of resistance (most to least): Prions, Endospores of bacteria, Mycobacteria, Cysts of protozoa, Vegetative protozoa, Gram-negative bacteria, Fungi, Viruses without envelopes, Gram-positive bacteria, Viruses with lipid envelopes

    Aim of Sterilization & Asepsis

    • Asepsis: Practice to reduce or eliminate contaminants.
    • Ideal situation: contaminant-free field ("sterile"). This is difficult to achieve, with the goal being elimination of infection rather than absolute sterility.

    Methods of Sterilization

    • Physical agents
    • Chemical agents
    • Mechanical removal methods

    Physical Agents

    • Heat (Dry, Moist)
    • Radiation (Ionizing, Non-ionizing)

    Dry Heat

    • Kills by oxidation effects
    • Operates between 50°C to 250/300°C
    • A holding period of 160°C for 2 hrs is desirable
    • Temperature controlled by thermostat
    • Double-walled insulation keeps heat in and conserves energy
    • Uses: to sterilize forceps, scissors, scalpels, swabs, pharmaceuticals (liquid paraffin, dusting powder, fats, and grease)

    Flaming/Incineration

    • Method of destroying materials: contaminated cloth, animal carcasses, and pathological materials

    Moist Heat Sterilization

    • Kills microorganisms by coagulating their proteins (changes proteins structure).
    • Methods:
      • Temp below 100°C ("Pasteurization")
      • Temperature at 100°C: Boiling
      • Steam at atmospheric pressure: Koch/Arnold's steamer
      • Steam under pressure: Autoclave

    Pasteurization

    • Process of killing pathogens in milk but does not sterilize it
    • Milk heating at 63°C for 30 minutes (Holder method).
    • Heating milk at 72°C for 15-20 seconds and rapidly cooling to 13°C (Flash process)

    Hot Water Bath

    • To inactivate non-sporing bacteria for vaccines.
    • Bath at 60°C/one hour.
    • Serum or body fluids containing coagulable proteins can be sterilized by heating for 1 hr at 56°C in a water bath (several successive days)

    Temperature at 100°C

    • Kills vegetative forms of bacterial pathogens/
    • Hepatitis virus can survive up to 30 minutes of boiling.
    • Endospores can survive up to 20 hours or more of boiling.

    Steam Under Pressure - Autoclave

    • Works on the principle of steam under pressure.
    • Invented by Charles Chamberland in 1879
    • Autoclave consists of a vertical or horizontal cylinder with a lid for keeping materials to be sterilized.
    • Pressure gauge to measure Pressure, Safety valve to permit steam escape.
    • Sterilization 121°C for 15 minutes or 132°C for 3 minutes.
    • Quality control is important

    Chemical Agents

    • Protein coagulation
    • Disruption of the cell membrane
    • Removal of sulfhydryl groups
    • Substrate competition

    Principles of Effective Disinfection

    • Concentration of disinfectant
    • Organic matter
    • pH
    • Time

    Alcohols

    • Ethanol/isopropyl alcohol are frequently used.
    • No action on spores.
    • Concentration is recommended at 60-90% in water.
    • Uses: disinfectant of clinical thermometers, skin disinfectant (venupuncture)

    Aldehydes

    • Formaldehyde & Glutaraldehyde are frequently used.
    • Formaldehyde is bactericidal, sporicidal, and lethal to viruses.
    • Glutaraldehyde is effective against tubercle bacilli, fungi, and viruses.
    • Formaldehyde uses: Preserves anatomical specimens, destroys Anthrax spores, sterilizes metal instruments (10% formalin + 0.5% sodium tetraborate).
    • Glutaraldehyde uses: Treatments for corrugated rubber tubes, facemasks, plastic endotracheal tubes, and polythene tubing

    Halogens

    • Iodine in aqueous and alcoholic solutions for skin disinfection.
    • Actively bactericidal with moderate activity against spores.
    • Chlorine and its compounds: disinfectant in water supplies and swimming pools.

    Phenols

    • Obtained by coal tar distillation.
    • Phenols are powerful microbicidal substances.
    • Phenol derivatives are widely used as disinfectants in hospitals (e.g., Lysol, cresol).

    Hydrogen Peroxide

    • Hydrogen peroxide is used as an antiseptic to clean wounds and disinfect contact lenses.
    • Effectiveness is limited by the organism's ability to produce catalase (enzyme degrading H2O2).
    • Hydrogen peroxide is an oxidizing agent that attacks sulfhydryl groups, thereby inhibiting enzymatic activity.

    Gases

    • Ethylene oxide: Colorless, ethereal-smelling gas with high penetration.
    • Effective against all microbes, including viruses and spores.
    • Used to sterilize heart-lung machines, respirators, sutures, dental equipment, books and clothing.
    • Sterilizes glass, metal, paper surfaces, plastics, oil, some foods and tobacco.

    Metallic Salts

    • Salts of silver, copper, and mercury are used as disinfectants.
    • Act by coagulating proteins.
    • Marked bacteriostatic, weak bactericidal, and limited fungicidal activity.

    Sterilization by Filtration

    • Filtration removes bacteria from heat-labile liquids (sera and solutions of sugar, antibiotics).
    • Filters used: Candle filters, Asbestos filters, Sintered glass filters, Membrane filters

    Radiation

    • Non-ionizing radiation (e.g., UV rays): Absorbed as heat, used in rapid mass sterilization of prepacked syringes and catheters
    • Ionizing radiation (e.g., X-rays, gamma rays, cosmic rays): High penetrative power, cold sterilization, sterilizing plastics, syringes, catheters, grease fabrics, metal foils.

    Ultrasonic and Sonic Vibration

    • Bactericidal activity
    • Microorganisms vary in sensitivity, limited practical value for sterilization/disinfection.

    Table 3-1: Methods of Sterilization

    Table 3-2: Methods of Disinfection

    Table 3-3: Antiseptic Agents

    Table 3-4: Germicidal properties (properties of disinfectants & antiseptic agents)

    References

    • Murray, Patrick R., MEDICAL MICROBIOLOGY, EIGHTH EDITION ISBN: 978-0-323-29956-5
    • Lippincott's Illustrated Reviews Microbiology, 3rd Edition (Richard A. Harvey, Cynthia Nau Cornelissen, Ph.D)
    • Jawetz Melnick & Adelbergs Medical Microbiology
    • Review of Medical Microbiology and Immunology, Fourteenth Edition (Warren Levinson, MD, PhD)
    • www.cdc.com

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    Sterilization, Disinfection, and Antisepsis PDF

    Description

    Test your knowledge on various microbial control methods in this quiz, which includes topics such as moist heat sterilization, pasteurization, and the action of disinfectants. It covers the primary mechanisms of sterilization and the effectiveness of different agents against microorganisms. Perfect for students in microbiology or those interested in infection control.

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