Microorganism Control and Asepsis Notes
Techniques for Controlling Pathogenic Microorganisms
- Methods to control microorganism growth and infectious disease transmission involve:
- Stopping microorganism growth temporarily
- Reducing microorganism numbers to safe levels
- Destroying microorganisms
- Sterilization
- Destruction of all microorganisms, including endospores.
- Sterilization agents kill all living things, removing the source of contagion.
- Disinfection
- Destruction of pathogens (but not endospores).
- Reduces pathogen number or inhibits growth to a non-disease-producing level.
- Disinfection agents kill some microbes and inhibit others.
- Antisepsis
- Chemical disinfection of skin, mucosal membranes, or other living tissues.
- Sanitation
- Reduction/removal of pathogens on inanimate objects via chemical cleansing.
- Germicide
- Chemical agent that kills microorganisms.
- Specific germicides include: sporicide, bactericide, viricide, and fungicide.
Factors for Effective Microbial Control
- Population size.
- Types of microorganisms present.
- Physiological state of microorganisms.
- Microorganism susceptibility to the agent.
- The environment where they are growing.
- Concentration of the dose used.
- Duration of treatment.
Methods of Microbial Control
Physical Methods
- Exclude microbes or reduce their numbers in a solution or on a surface.
- Filtration: Passing solutions or gases through a device to trap microbes.
- Desiccation: Removal of moisture; many bacteria are sensitive to water loss.
- Lyophilization: Rapid water removal under cold temperatures and partial vacuum.
- Radiation: Matter releases energy, atomic particles, or both.
- Temperature: Can denature proteins, causing them to lose their 3D shape.
- Flaming and incineration: Completely destroy all life.
- Dry heat: Hot air is used, but many spore formers can withstand it.
- Moist heat: Works well for most microbes but not thermoduric organisms or spore formers.
- Autoclave: Uses saturated steam for effective sterilization.
- Thermal death point (TDP): Temperature at which all growth stops.
- Thermal death time (TDT): Time to kill all microbes in a sample.
- Decimal reduction factor: Time at specific heat to reduce microbe population tenfold.
Chemical Methods
- Application of chemical agents to inhibit growth or kill microbes on fomites or skin.
- Microbiocidal agents kill all living cells.
- Microbiostatic agents kill some cells and inhibit the growth of others.
- Antibiotics
- Antiseptics
- Disinfectants
- Preservatives
Classifications of Chemical Agents
- High-level germicides: Sterilize fomites but are toxic to skin/mucous membranes.
- Aldehydes (formaldehyde and glutaraldehyde): Fix tissues by alkylating and forming cross-links between proteins.
- ß-propiolactone: Sterilizes bone grafts; breaks down into nontoxic compounds but can burn skin.
- Intermediate-level disinfectants/antiseptics: Kill and inhibit on fomites/skin but can be toxic at medium to high concentrations.
- Phenol: Denatures proteins and destabilizes cell membranes; bactericidal, fungicidal, and viricidal at high concentrations; effective against mycobacteria, staphylococci, streptococci, and gram-negative coliforms (e.g., E. coli) but not endospores.
- Phenol Coefficient: Mathematical value comparing disinfectant effectiveness to phenol.
- Ethylene Oxide: Kills vegetative cells and spores; used in a chamber (similar to an autoclave) at 60°C for 1-10 hours, mixed in a 9:1 ratio with carbon dioxide to reduce toxicity and flammability.
- Ozone: Powerful oxidizing agent that kills cells and spores on glassware, surgical implements, and bandages; outgasses quickly, leaving no toxic residues.
- Includes alcohols, iodophors, and phenols
- Used for laryngoscopes, fiber optic endoscopes
- Low-level disinfectants: Kill some microbes but inhibit the growth of most.
- Alcohols: Effective antiseptics/disinfectants at 70-80% concentrations; kill by denaturing proteins, dehydrating, and disrupting cell membrane phospholipid structure but are relatively ineffective against spores and viruses.
- Hydrogen peroxide: Low-level disinfectant at ≤3% concentrations; higher concentrations are caustic; used as an antiseptic for minor cuts/scrapes and as a bleaching agent.
- Heavy metals: Combine with sulfur groups in microbial proteins, causing denaturation; some of the earliest control agents.
- Detergents and soaps: Composed of lipids and compounds with basic pH (e.g., sodium hydroxide); detergents are anionic or cationic, releasing negatively or positively charged ions.
- Halogens
- High affinity for electrons, making them very reactive with biological molecules, disrupting enzyme activity, breaking down lipid structure, and producing oxidizing agents.
- Chlorine: Used as a disinfectant only, effective against many vegetative forms of microbes.
- Iodine: Lethal to all vegetative forms of microorganisms, can inactivate viruses, and effective in higher concentrations against endospores.
- Iodophore Compounds: Iodine dissolved in mild detergent and alcohol.
- Anionic forms: Weakly active against gram-positive bacteria due to repelling negatively-charged cells.
- Cationic forms: Attracted to bacterial cells and are bacteriostatic, while remaining relatively mild to the surface of skin.
- Quaternary ammonium compounds (QUATS): Cationic detergents with long-chain alkyl groups.
- Dyes: Can not be used to stain microorganisms, but also have antimicrobial activity
- Crystal violet can be used to treat oral infections by bacteria as Rochlaemia Quintana the agent to trench mouth, and fungal infections such as Candida albicans, which causes oral thrush
Asepsis
- Terms related to suppression of microorganisms
- Aseptic Technique: Precautionary steps to prevent contamination of sterile environment
- Minimize number of personnel taking part in procedure
- Keeping the conversations at a minimum as much as possible
- Reduce movements inside the operating theatre
- Use of non-perforating devices
- Maintaining a fair distance of non-scrubbed staff away from the scrubbed staff.
Types of Asepsis
- Medical Asepsis: Reduction of the number of disease-causing agents and their spread
- Techniques are called clean techniques.
- Methods: Isolation of the patient, Hand washing, Preventive Vaccination, Increasing awareness, Gloves, masks and gowns, use of chemical agent
- Applications: administration of enemas, medications, tube feedings, etc.
- Surgical Asepsis: Complete elimination of disease-causing agents and their spores from the surface of an object.
- Sterile techniques are used
- Involves: Proper maintenance and preparation/disinfection of the environment, Sterilization surgical equipment, Scrubbing of personnel involved in the procedure, Adequate cleaning of the site
- Applications: Changing dressings of a wound, catheterization, and surgeries
Antimicrobial Agents in Therapy
- Antimicrobial: Agent that destroys microbes, inhibits their growth, or prevents or counteracts their pathogenic action.
- Antibiotics: Substances produced by one microorganism that kill or prevent the growth of another microorganism.
- Today, the term refers to almost any drug that attempts to rid your body of a bacterial infection.
- Chemotherapy: Any chemical treatment intended to be therapeutic with respect to a disease state.
- Infection: An uncontrolled growth of harmful microorganisms in a host.
- Selective toxicity: Ability of a drug to target sites specific to the microorganism responsible for infection.
- Superinfection: Additional infection that happens during or immediately after an existing infection; usually by a drug-resistant organism.
- Antimicrobials: simple overview
- Antibiotics: classification
Spectrum of Antimicrobial Activity
- Broad-spectrum: Affects a wide range of microbes.
- Narrow-spectrum: Targets specific types of microbes.
Action of Antimicrobial Drugs
- Inhibiting cell wall synthesis
- Inhibiting protein synthesis
- Injuring the plasma membrane
- Inhibiting nucleic acid synthesis
- Inhibiting synthesis of essential metabolites
Common Antimicrobial Drugs
- Antibacterial Drugs
- Beta-lactam antibiotics
- Antibiotics from prokaryotes
- Antimycobacterial antibiotics
- Antifungal Drugs
- Antiviral Drugs
- Antiprotozoan and Antihelminthic Drugs
Sensitivity Test
Resistance to Antimicrobial Drugs
- Mechanisms of Resistance
- Enzymatic destruction or inactivation of the drug
- Prevention of penetration to the target site within the cell wall
- Alteration of the drug's target site
- Rapid efflux of the antibiotic
- Evolution of microbial resistance to drugs
- Antibiotic Misuse
Antibiotic Safety
- Side effects: Results of drug or other therapy in addition to or in extension of the desired therapeutic effect, usually but not necessarily, connoting an undesirable effect
- Adverse effects/adverse drug reactions: Undesirable, uncomfortable, or dangerous effects that a drug may have
- Drug toxicity: Adverse effects of a drug that occur because the dose or plasma concentration has risen above the therapeutic range
- Drug abuse: The misuse of recreational or therapeutic drugs that may lead to addiction or dependence, serious physiological injury, psychological harm, or death.
- Anaphylaxis: Sudden, life-threatening, whole body reaction to a drug or other allergen and characterized by irregular heartbeat, trouble breathing, swelling, and unconsciousness
- Hypersensitivity Test
Drug Interactions
- Synergism: 2+ or more drugs work together against one target, producing a greater combined effect.
- Antagonism: one drug reduces or blocks the effect of another
- Potentiation: Drug A boosts the effects of drug B, often by increasing drug B levels in the blood.
- Additive toxicity: Combinations of drugs may result in greater toxicity than would be seen with single drugs.