Microbial Control and Host Defenses Lecture Review

PHYSICAL AND CHEMICAL METHODS OF MICROBIAL CONTROL

A. Terminology

At the conclusion of this lecture, you should be familiar with ALL terms described in our lecture notes. Below is a list of key terminology that you should be able to identify and/or comprehend if used in a sentence. Suggestion: list definitions or make flashcards ONLY for terms that you are unfamiliar with or for terms that sound similar but have different meanings. Use your list or flashcards to actively quiz yourself!

Germicidal: Agents that kill germs.
Bactericidal: Agents that kill bacteria.
Bacteriostatic: Agents that inhibit the growth of bacteria.
Sporicidal: Agents that kill bacterial spores.
Fungicidal: Agents that kill fungi.
Fungistatic: Agents that inhibit the growth of fungi.
Virucidal: Agents that kill viruses.
Sterilization/Sterilant/Sterile: The process of eliminating all microorganisms, including spores.
Disinfection/Disinfectant/Disinfected: The process of eliminating many or all pathogenic microorganisms, except bacterial spores, from inanimate objects.
Antisepsis/Antiseptic: The process of eliminating many or all pathogenic microorganisms on living tissues.
Sanitization/Sanitizer: The process of reducing the number of pathogenic microorganisms to a safe level.
Decontamination: The process of cleansing an item to remove contaminants.
Preservation: The process of maintaining the quality and safety of food products.

Mode of Action

Heat
- Dry Heat: Kills microorganisms through oxidation and denaturation of proteins.
- Moist Heat: Involves water that allows for faster penetration; includes methods like boiling or autoclaving.
- Pasteurization: A process that heat-treats food to kill pathogens while preserving flavor and nutrients.
- Boiling Water: Destroys most microorganisms but not spores.
- Steam Heat Under Pressure: Achieved in an autoclave to sterilize equipment.
Low Temperatures
- Refrigeration: Slows microbial growth.
- Freezing: Stops growth and reproduction of microorganisms.
Radiation: Uses UV or gamma rays to kill microorganisms.
- UV Irradiation: Used primarily for surface sterilization.
- Gamma Irradiation: Used for sterilizing medical supplies and food.
Filtration: Separates microbes from liquids and gases.
Dehydration/Dessication: Removes moisture, inhibiting microbial growth.

Chemical Agents

Halogens: Chlorine, Chlorites, and Iodine are common disinfectants.
Aldehydes: Formaldehyde and Glutaraldehyde are used for sterilization.
Hydrogen Peroxide: Antiseptic and disinfectant.
Alcohols: Ethanol/ethyl alcohol and Isopropanol are commonly used antiseptics.
Chlorhexidine: Used as an antiseptic in medical settings.
Phenolics: Triclosan is an example used in household products.
Quaternary Ammonium Compounds: Amphipathic surfactants used as disinfectants.
Vinegar/Acetic Acid: Used in food preservation.
Ammonia: Acts as a cleaning agent.
Heavy Metals: Such as silver and mercury, used for their antimicrobial properties.
Osmolarity and Salinity: Affect microbial growth through the movement of water.
Soaps: Emulsify and remove microbial contaminants.

ANTIMICROBIALS

C. Terminology

Antimicrobial: Agents that kill or inhibit the growth of microbes.
Chemotherapeutic agent: Drugs used to treat infections.
Antibiotic: Substances produced by microorganisms that inhibit or destroy other microorganisms.
Narrow-spectrum: Antibiotics effective against specific types of bacteria.
Broad-spectrum: Antibiotics effective against a wide range of bacteria.
β-lactam drugs: Include Penicillin and related antibiotics that inhibit cell wall synthesis.
- Penicillin: First antibiotic discovered, effective against Gram-positive bacteria.
- Methicillin: A beta-lactam antibiotic, resistant to some penicillinases.
- Amoxicillin: Extended-spectrum penicillin effective against a broader range of bacteria.
Cephalosporins: Similar to penicillin, used for cephalosporin-resistant bacteria.
- Cephalothin: Used for treatment of infections by Gram-negative bacteria.
Carbapenems: Have a broad spectrum and are highly resistant to β-lactamases.
Vancomycin: A glycopeptide antibiotic used for serious Gram-positive infections.
Bacitracin: Effective against Gram-positive bacteria used topically.
Aminoglycosides: Target bacterial ribosomes, e.g., Streptomycin.
Tetracycline: Interferes with protein synthesis and has broad-spectrum activity.
Macrolide drugs: Erythromycin and Azithromycin, inhibit protein synthesis.
Fluoroquinolones: Ciprofloxacin inhibits bacterial DNA synthesis.
Rifampin: Inhibits RNA synthesis and is effective against tuberculosis.
Metronidazole: Effective against anaerobes and protozoa.
Fluconazole: Antifungal used for yeast infections.
Sulfonamides (Sulfa drugs): Inhibit folic acid synthesis in bacteria.
Antifungals: Target fungal cells with selective toxicity.
Antivirals: Agents targeting viral replication processes.
Antimicrobial susceptibility: Refers to how susceptible a microbe is to the effects of an antimicrobial agent.
Antimicrobial resistance: The ability of microbes to resist the effects of drugs that previously worked to treat them.
Multi-drug resistant bacteria: Pathogens that are resistant to multiple treatments, examples include Clostridium difficile, MRSA, VRE, CRE.

MICROBE – HUMAN INTERACTIONS

A. Terminology

Mutualistic: Relationship where both organisms benefit.
Commensalistic: One organism benefits while the other is neither helped nor harmed.
Parasitic: One organism benefits at the expense of the other.
Human microbiome/normal microbiota: The collection of microorganisms living in and on the human body.
Probiotics: Live microorganisms intended to provide health benefits.
Prebiotics: Substances that induce the growth of beneficial microorganisms.
Infection/Infectious disease: A condition where pathogens invade and multiply in the host.
Pathogen: Any microorganism that can cause disease.
Virulence factor: A trait of a microbe that promotes pathogenicity.
Opportunistic pathogen: Organisms that cause disease only in weakened hosts.
Primary infection: The first infection caused by a pathogen.
Secondary infection: Infection caused by a different pathogen following a primary infection.
Acute infection: Rapid onset and duration.
Chronic infection: Long-lasting and persistent.
Latent infection: Inactive infections that can reactivate later.
Endogenous infection: Infection caused by the organism's own microbiota.
Nosocomial infection: Hospital-acquired infections.
Zoonosis: Diseases transmitted from animals to humans.
Portal of entry: The route through which a pathogen enters the host.
Exogenous port of entry: Introduced from outside the body.
Endogenous port of entry: Originates from the host’s own microbiota.
Fimbrae: Hair-like structures that aid in attachment of bacteria to surfaces.
Capsules: Protective layers that enhance virulence.
Surface proteins: Enable pathogen attachment.
Spikes: Used by viruses to attach to host cells.
Phagocytes: Cells that engulf and destroy pathogens.
Phagocytosis: The process in which a cell engulfs particles.
Leukocidins: Substances that kill white blood cells.
Exoenzymes: Enzymes secreted by bacteria that break down barriers.
Toxin: A poisonous substance produced by living cells.
Endotoxin: A component of the Gram-negative bacteria cell wall, can trigger severe immune responses.
Exotoxin: Toxins released into the surrounding environment by bacteria.
Hemolysin: An exotoxin that lyses red blood cells.
Neurotoxin: Toxins that affect the nervous system.
Enterotoxin: Affects the intestinal tract.
Disease transmission: Mechanisms through which an infection is spread.
Communicable disease: Disease transmitted from one person to another.
Contagious: Easily transmitted from person to person.
Direct transmission: Immediate transfer of pathogens.
Direct contact: Physical contact between hosts.
Droplets: Small particles containing pathogens expelled by coughing or sneezing.
Vertical transmission: Pathogen passed from mother to child.
Indirect transmission: Pathogens spread through intermediaries.
Aerosols: Droplets that remain suspended in the air.
Vehicle: Inanimate material used as a transmission source.
Fomites: Objects that may carry infectious agents.
Contaminated food/water: Sources of pathogen transmission.
Fecal-oral route of transmission: Transfer of pathogens from feces to mouth.
Vector: An organism that transmits disease.
Non-communicable disease: Diseases that do not spread from person to person.
Epidemiology: The study of how diseases spread and can be controlled.
Prevalence: The total number of cases of an infection in a population at a given time.
Incidence: The number of new cases of disease in a population over a specific period.
Mortality rate: The percentage of deaths from a disease in a given population.
Epidemic: A sudden increase in the number of cases of a disease.
Pandemic: Widespread occurrence of a disease across countries or continents.
Endemic: A disease regularly found within a certain geographic area.
Sporadic outbreak: Occasional occurrences of a disease in a population.

HOST DEFENSES

A. Terminology

First line of defense: Physical and chemical barriers to prevent pathogen entry.
Second line of defense: Non-specific immune responses, including inflammation and phagocytosis.
Third line of defense: Specific immune responses involving antibodies and lymphocytes.
Non-specific defenses: General defenses that do not target specific pathogens.
Specific immunity: Targeted response against specific antigens.
Innate defenses: Natural defenses present at birth.
Barrier defenses: Physical defenses like skin and mucous membranes.
Innate immunity: Immediate response to pathogens, including inflammatory responses.
Adaptive immunity: Tailored responses against specific pathogens, develops upon exposure.
Physical/anatomical barriers: Structures like skin that block pathogen entry.
Chemical barriers: Secretions that neutralize pathogens, such as lysozyme in tears.
Lysozyme: An enzyme that destroys bacterial cell walls.
Antimicrobial peptides: Small proteins that kill microbes or inhibit their growth.
Sebum: Oily substance that has antimicrobial properties.
Immunology: The study of the immune system and its responses.
Immunity: The ability of an organism to resist disease.
Immune system: The body system responsible for providing immunity against pathogens.
Lymphatic system: Network of vessels and nodes that play a role in immune responses.
Lymphatic vessels: Transport lymph, a fluid containing immune cells.
Lymph: Clear fluid that circulates throughout the lymphatic system.
Thymus gland: Maturation site for T cells.
Lymph nodes: Filter lymph and house immune cells.
Lymphatic tissue: Collection of lymphocytes and other immune cells.
Spleen: Filters blood and maintains the health of red blood cells while storing white blood cells.
Blood: Carry nutrients, gases, and immune cells throughout the body.
Plasma: The liquid component of blood that carries cells and nutrients.
Hematopoiesis: The process of blood cell formation.
Stem cells: Unspecialized cells that can differentiate into various blood cells.
Bone marrow: Primary site of hematopoiesis where blood cells are made.
Erythrocytes: Red blood cells responsible for oxygen transport.
Thrombocytes: Platelets that aid in blood clotting.
Leukocytes: White blood cells that are the primary cells of the immune response.
- Granulocytes: White blood cells that contain granules in their cytoplasm.
- Neutrophils: First responders to infection, engulf pathogens.
- Basophils: Involved in inflammatory responses, release histamines.
- Eosinophils: Combat parasites and involved in allergic responses.
- Agranulocytes: White blood cells without granules.
- Monocytes: Differentiate into macrophages and dendritic cells.
- Macrophages: Phagocytes that engulf and digest pathogens; activate T cells.
- Dendritic cells: Antigen-presenting cells that stimulate T cells.
- Lymphocytes (adaptive immune response):
  - B cells: Produce antibodies against antigens.
  - T cells: Mediate immune responses.
  - Helper T cells: Assist other immune cells.
  - Cytotoxic T cells: Directly kill infected cells.
Phagocytosis: The process by which phagocytes engulf and destroy pathogens.
Phagocyte: Cells that perform phagocytosis.
Inflammation: The body's localized response to injury or infection.
Fever: An increase in body temperature as a response to infection.
Humoral immunity: Antibody-mediated immunity by B cells.
Antigen: Any substance that can trigger an immune response.
Antibody: Proteins produced by B cells that bind to specific antigens.
Antigen-presenting cell: Cells that display antigens to T cells to initiate an immune response.
Cell-mediated immunity: Immune response that does not involve antibodies but involves T cells.
Naturally acquired immunity: Immunity gained through natural processes.
Artificially acquired immunity: Immunity gained through deliberate exposure, such as vaccination.
Active immunity: Immunity developed after exposure to an antigen.
Passive immunity: Immunity obtained from another individual, such as antibodies passed from mother to child.
Vaccination: Introduction of an antigen to stimulate an immune response.
Herd immunity: When a large portion of a community becomes immune to a disease, making its spread unlikely.
Inactivated vaccine: Contains killed pathogens that cannot cause disease.
Attenuated vaccine: Contains weakened pathogens capable of inducing an immune response without causing disease.