Microbial Control and Sterilization Techniques
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Questions and Answers

What is the primary goal of sterilization?

  • Reduction of microbial load
  • Disinfection of surfaces
  • Removal of vegetative pathogens
  • Destruction or removal of all forms of microbial life (correct)

    • Which of the following methods is most effective for commercial sterilization?

  • Heating to kill all vegetative bacteria
  • Sufficient heat to kill endospores of Clostridium botulinum (correct)
  • Using antimicrobial agents in food
  • Boiling for 10 minutes

    • Which factors influence the effectiveness of antimicrobial treatment?

  • Time of exposure (correct)
  • Shape of the microbial cells
  • Source of microbial contamination
  • Color of the microorganism

    • What is the best description of Thermal Death Point (TDP)?

    <p>Lowest temperature at which all cells in a culture are killed in 10 minutes</p> Signup and view all the answers

    What is the role of moist heat sterilization in microbial control?

    <p>It denatures proteins, effectively killing microorganisms</p> Signup and view all the answers

    What is the primary function of beta-lactamases in bacterial resistance?

    <p>Destruction of the penicillin beta-lactam ring</p> Signup and view all the answers

    Which mechanism of antibiotic resistance involves altering the openings in the bacterial cell membrane?

    <p>Prevention of penetration of the drug</p> Signup and view all the answers

    What type of resistance is associated with MRSA?

    <p>Methicillin resistance</p> Signup and view all the answers

    Which factor contributes to the projection of 10,000,000 antibiotic resistance-related deaths annually by 2050?

    <p>Improper antibiotic usage</p> Signup and view all the answers

    What impact does antibiotic resistance have on medical procedures?

    <p>Reduces the success of artificial replacements</p> Signup and view all the answers

    What is the primary mechanism by which aldehydes function as disinfectants?

    <p>Cross-linking with functional groups</p> Signup and view all the answers

    Which of the following is a feature of ethylene oxide as a gaseous sterilant?

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

    Hydrogen peroxide is commonly used as an antiseptic, but it has limitations. What is a significant drawback?

    <p>It slows down wound healing</p> Signup and view all the answers

    Peracetic acid is known for its rapid disinfection capabilities. What is one of its main advantages?

    <p>Leaves no toxic residues</p> Signup and view all the answers

    What characteristic of Gram-negative bacteria can impede chemical disinfection?

    <p>Presence of lipopolysaccharide layers</p> Signup and view all the answers

    What is a common use for glutaraldehyde in a healthcare setting?

    <p>Disinfecting hospital instruments</p> Signup and view all the answers

    Which of the following statements about ozone (O3) is true?

    <p>It is highly reactive and generated through electrical discharges</p> Signup and view all the answers

    Which organic acid is commonly used for controlling molds in food?

    <p>Sorbic acid</p> Signup and view all the answers

    What is the most effective condition for sterilization in an autoclave?

    <p>Direct contact with steam or in an aqueous solution</p> Signup and view all the answers

    Which temperature and pressure conditions are necessary for sterilization in an autoclave?

    <p>121°C and 15psi</p> Signup and view all the answers

    What is the purpose of pasteurization?

    <p>To reduce spoilage organisms and pathogens</p> Signup and view all the answers

    Which of the following is true about biguanides like chlorhexidine?

    <p>They disrupt plasma membranes and are low in toxicity to skin.</p> Signup and view all the answers

    What is the likely mode of action for iodine as a disinfectant?

    <p>It combines with amino acids of enzymes and proteins.</p> Signup and view all the answers

    Which disinfectant is effective as a strong oxidizing agent to prevent enzyme action in cells?

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

    What is steam sterilization most effective for?

    <p>Killing endospores and all organisms.</p> Signup and view all the answers

    What is a key characteristic of ultra-high temperature (UHT) processing?

    <p>Involves heating to 140°C for a short period.</p> Signup and view all the answers

    What mechanism do aminoglycosides utilize to inhibit bacterial protein synthesis?

    <p>Change shape of the 30S subunit</p> Signup and view all the answers

    Which antibiotic is effective against vancomycin-resistant bacteria?

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

    Which side effect is associated with the use of tetracyclines?

    <p>Discoloration of teeth in children</p> Signup and view all the answers

    What does the term 'MIC' refer to in antibiotic therapy?

    <p>Minimal inhibitory concentration</p> Signup and view all the answers

    Which method is used to determine the minimal inhibitory concentration of antibiotics?

    <p>Broth dilution tests</p> Signup and view all the answers

    What is a common consequence of the misuse of antibiotics?

    <p>Selection for resistance mutants</p> Signup and view all the answers

    Which of the following antibiotics is a broad-spectrum antibiotic effective against intracellular bacteria?

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

    Which antibiotic class binds to the 50S ribosomal subunit and prevents translocation?

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

    What is the main action of sulphonamides in bacterial treatment?

    <p>Inhibit folic acid synthesis</p> Signup and view all the answers

    Which antibiotic is specifically noted for treating urinary tract infections?

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

    What is the primary action of penicillin in bacterial cells?

    <p>Prevents peptidoglycan synthesis</p> Signup and view all the answers

    Which of the following antibiotics is known for its broad-spectrum activity?

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

    What does the term 'bacteriostatic' refer to?

    <p>Drugs that inhibit bacteria from growing</p> Signup and view all the answers

    Which of the following statements about cephalosporins is correct?

    <p>They are resistant to penicillinase.</p> Signup and view all the answers

    What is a potential consequence of using broad-spectrum antibiotics?

    <p>Development of antibiotic resistance</p> Signup and view all the answers

    Nisin, an antibiotic used in food preservation, primarily prevents the growth of which type of bacteria?

    <p>Endospore-forming spoilage bacteria</p> Signup and view all the answers

    What is the main source of penicillin?

    <p>Mould known as Penicillium notatum</p> Signup and view all the answers

    Which of the following describes the role of sodium nitrate and nitrite in processed meats?

    <p>Preserve red meat color</p> Signup and view all the answers

    What is aztreonam's main characteristic?

    <p>Works against only certain gram-negatives</p> Signup and view all the answers

    Which antibiotic is considered the last line of defense against MRSA?

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

    Study Notes

    Microbial Control Methods

    • Physical agents: Heat, radiation, gases, liquids, and mechanical removal methods.
    • Heat: Used to denature enzymes and modify protein structures within microorganisms.
      • Thermal death point (TDP): Lowest temperature at which all cells in a culture are killed in 10 minutes.
      • Thermal death time (TDT): Time to kill all cells in a culture.
      • Moist Heat Sterilization: Kills by denaturing proteins through breaking hydrogen bonds, effective in boiling water or steam sterilization. Reliable sterilization needs temperatures above water's boiling point. Exception: some hepatitis viruses can survive boiling for up to 30 minutes. Some bacterial endospores can survive 20+ hours. Effective when organisms are directly in contact with the steam or in an aqueous solution. Steam and pressure (15psi/121°C) kills organisms and endospores in ~15 minutes in an autoclave.
      • Dry Heat Sterilization: Kils by oxidation. methods include flaming, incineration, and hot-air sterilization.
      • Pasteurization: Reduces spoilage organisms and pathogens in foods. Includes 63°C for 30 minutes (milk), high-temperature, short-time (HTST): 72°C for 15 seconds
      • Ultra-high temperature (UHT): 140°C for <1 second for sterilization, refrigeration not required.
    • Radiation: Damages DNA through ionizing and nonionizing radiation.
      • Ionizing radiation: X-rays, gamma rays, and electron beams. Carry more energy, pass through solids. Useful for low-level processing of spices, meats, and vegetables. Also for high-energy treatment of medical supplies, and mail.
      • Nonionizing radiation: UV light damages DNA by cross-linking. Used for surface sterilization in hospitals. Doesn't pass through solids.
    • Microwaves: Kills by heating up water. Not especially antimicrobial in most cases and heats food unevenly due to moisture distribution.
    • Cold: Low temperature inhibits microbial growth. Refrigeration and deep freezing methods are used. Slow freezing methods form ice crystals, disrupting bacterial cellular function and molecular structure. Thawing is even more damaging. Freeze-thaw cycles are highly damaging.
    • High pressure: Denatures proteins and alters carbohydrates. Kills endospores. Used in food treatment (e.g., fruit juices).
    • Desiccation: Removal of water stops metabolic activities. Used in food preservation methods such as freeze-drying (lyophilization)- coffee and food additives for dry cereals.
    • Osmotic pressure: High concentrations of salts and sugars (hypertonic) causes water to leave cells, effective in preservation of some foods (e.g., fruits and grains). Moulds and yeasts are resistant and can spoil food.
    • Filtration: Removes heat-sensitive microbes using membrane filters with pore sizes of 0.22 µm or 0.45 µm. Air filtration with HEPA filters have a pore size of 0.3 µm.

    Chemical Agents

    • Chemical agents: Most reduce microbial populations to safe levels.
    • Factors in effective disinfection: Concentration, nature of the material being disinfected(organic material in the material can interfere with the disinfectant), time, and the contact period needed for effective disinfection.
    • Evaluation of disinfectants: Disk-diffusion method (Kirby-Bauer test) is used for effective disinfectant evaluation. Filter disks soaked with known concentrations of disinfectants are placed on an agar plate with a lawn of bacteria. The zone of inhibition is measured to determine the effectiveness of a particular disinfectant.

    Antimicrobial Agents

    • Antimicrobial Actions: Common actions for killing microbes include alteration of membrane permeability, protein damage, and nucleic acid damage.
    • Types of Disinfectants:
      • Phenols & Phenolics: Disrupt plasma membranes. Effective in organic matters such as pus, saliva, feces. Effective against Gram-positive Staphylococci, Streptococci bacteria, and mycobacteria.
      • Biguanides (Chlorhexidine): Disrupt plasma membranes. Can be used with detergents and alcohol in surgical hand scrubs. Low toxicity to the skin. Biocidal to most bacteria and fungi, but not sporicidal. Not effective against mycobacteria, endospores, and protozoan cysts.
      • Halogens (Iodine): Exact mode of action unknown, probably combines with amino acids of enzymes and cellular proteins Effective against all types of bacteria, many endospores, various fungi and some viruses. Available in aqueous alcohol solution (tincture) or as an iodophor. Ex: Betadine.
      • Halogens (Chlorine): Strong oxidizing agent. Prevents cellular enzyme system functioning. Used as a gas or in water as hypochlorous acid (HOCl). Can be used for disinfecting drinking water and swimming pools. Chloride compounds such as sodium hypochlorite (NaOCl) or bleach are common household disinfectants. Chloramines contains chlorine and ammonia. Used as a glassware and eating utensil sanitizer and municipal drinking water treatment, but toxic to fish.
      • Alcohols (Ethanol, Isopropanol): Denatures proteins, dissolves lipids, disrupts membranes. Effective before evaporating, leaving no residue. Kills bacteria and fungi but not non-enveloped viruses or endospores. Not effective in wounds as it causes coagulation of protein, preventing bacterial growth
      • Heavy Metals: Oligodynamic action by small amounts. Denatures proteins. Silver with other antimicrobials effective against burns, wounds. Mercury often more toxic and used to control mildew in paints. Copper sulfate used as an algaecide in reservoirs, ponds and swimming pools. Zinc chloride commonly used in mouthwashes, and zinc oxide most widely used for antifungal treatment.
      • Surface-active agents or surfactants (Soaps & Water): Not antiseptic, but acts as an emulsifier and cleans by washing away oil and dead cells. Acid-anionic (negatively charged) detergents react with plasma membranes, used as sanitizer for dairy utensils. Non-toxic, non-corrosive, and fast acting. Wide spectrum, including thermoduric bacteria.
      • Quaternary Ammonium Compounds: Positively charged cationic detergents. Denature proteins and disrupt plasma membranes. Bactericidal, especially against gram-positive bacteria. Fungicidal and virucidal against enveloped viruses. Doesn't kill endospores or mycobacteria. Some gram-negatives persist. Ex: Zephiran (Mr.Clean), Cepacol (cetyl pyridimium chloride).
      • Aldehydes: Inactivate proteins by cross-linking with functional groups (-NH2, -OH, –COOH, –SH). Used by morticians in embalming. Formaldehyde gas is highly effective. Formally available as formalin (37% aqueous solution). Glutaraldehyde used to disinfect hospital instruments. 2% solution effective (Cidex). Tuberculocidal, virucidal, and sporicidal for particular times.
      • Gaseous sterilants (Ethylene Oxide): Sterilize in a closed chamber. Denatures proteins and kills all microbes and endospores. Long exposure period (4-18 hrs). Mixed with non-flammable gases such as CO2 or nitrogen. Used for sterilizing hospital supplies and equipment.
      • Peroxygens (Oxidizing Agents): Highly reactive forms of oxygen. Generated by passing oxygen through high-voltage electrical discharges. Useful in neutralizing odors/tastes in water treatments using chlorine.
        • Ozone (O3): Highly reactive form of oxygen; generated by passing oxygen through high-voltage electrical discharges. Used with chlorine for neutralizing water taste and odor.
        • Hydrogen peroxide (H2O2): Common antiseptic in households and hospitals. Not suitable for open wounds as it slows down healing. Quickly broken down with catalase present in cells. Effective against aerobic and facultative anaerobic pathogens on inanimate surfaces. Increasing use in food industries. Ex: Benzoyl peroxide (anti-acne medication and treats wounds infected with anaerobes), Per-acetic acid (short disinfection, most effective liquid chemical used as sporicides, no toxic residues, minimal effect with organic matter).

    Microbial Characteristics and Control

    • Factors preventing chemical disinfection: lipopolysaccharide layer and porins for gram-negative bacteria; lipid-rich cell wall for mycobacteria. Bacterial endospores, fungal spores, protozoa, non-enveloped viruses, and prions are also resistant.

    Antibiotics

    • Sources of antibiotics: Streptomyces, Actinomycetes, Cyanobacteria.
    • Spectrum of activity: narrow-spectrum and broad-spectrum antibiotics.
      • Narrow spectrum: Affects a narrow range of types of microbes.
      • Broad spectrum: Affects a broad range of gram-positive and gram-negative bacteria.
    • Action of antibiotics: Various actions including inhibition of cell wall synthesis, protein synthesis, nucleic acid synthesis, and injury to the plasma membrane.
    • Types of antibiotics:
      • Inhibitors of cell wall synthesis: Penicillins, Cephalosporins, Vancomycin, Carbapenems, Monobactam.
      • Inhibitors of Protein Synthesis: Chloramphenicol, Aminoglycosides (Streptomycin, neomycin, gentamicin), Tetracyclines, Streptogramins, Macrolides, Oxazolidinones
      • Inhibitors of Nucleic Acid Synthesis (Quinolones and Fluoroquinolones): Inhibit DNA gyrase to stop DNA replication.
      • Competitive Inhibitors (Sulphonamides): Structural similarity to para-aminobenzoic acid. Inhibits folic acid synthesis
      • Injury to Plasma Membranes (Polymyxins): Injures the plasma membrane

    Drug Combinations

    • Synergism: When two drugs together produce a greater effect than either drug alone.
    • Antagonism: When two drugs together produce a lesser effect than either drug alone.

    Future Chemotherapeutic Agents

    • Antimicrobial peptides: products of the immune system (enzymes) produced in organisms.
    • Antisense agents: DNA sites causing pathogenic effects.
    • Phage therapy: Peptides produced by bacteriophages used as antimicrobials.

    Antibiotic Resistance

    • Misuse of antibiotics and causes of resistance: Using outdated or weakened antibiotics for inappropriate conditions. Using antibiotics in animal feed, not completing prescribed regimes, using someone else's leftover prescription.

    Minimal Inhibitory & Minimal Bactericidal Concentration

    • MICs: Minimal inhibitory concentration. The lowest antibiotic concentration that prevents visible bacterial growth.
    • MBCs: Minimal bactericidal concentration. The lowest antibiotic concentration that kills the microbes.

    Additional Information

    • Some facts: Penicillin was over-the-counter until the 1950s. Many antibiotics are still over-the-counter in developing countries. In the US, 50% of documented antimicrobial treatment is unnecessary. Factory farmed animals take antibiotics daily. Bacteria generation times are fast, which causes issues for making new drugs as resistance can develop quickly.
    • Deaths by 2050: Projections give significant death totals across the world.

    Methods Used to Evaluate Disinfectants

    • Disk-Diffusion Method: Filter disks soaked in disinfectants are placed on agar plates with bacterial lawns. Measurement of the zone of inhibition determines the effectiveness of the disinfectant.

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    Description

    Test your knowledge on microbial control and sterilization methods. This quiz covers important concepts such as the effectiveness of various sterilization techniques, the role of heat in microbial treatment, and mechanisms of antibiotic resistance. Challenge yourself and see how well you understand these critical principles.

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