Comprehensive Study Notes: unit 4

Hypersensitivity States

Definitions and Types

Hypersensitivity refers to undesirable reactions produced by the normal immune system, including allergies and autoimmunity. These reactions are classified based on the immune mechanism and timing.

• Hypersensitivity: An exaggerated or inappropriate immune response to an antigen.

• Allergen: A substance that causes an allergic reaction.

Types of Hypersensitivity

• Type I – Anaphylactic Reaction: Immediate, antibody (IgE)-mediated. Example: hay fever, asthma.

• Type II – Cytotoxic Reaction: Antibody-mediated destruction of cells. Example: hemolytic anemia.

• Type III – Immune Complex Reaction: Antigen-antibody complexes deposit in tissues, causing inflammation. Example: post-streptococcal glomerulonephritis.

• Type IV – Cell-Mediated Reaction: Delayed, T-cell mediated. Example: contact dermatitis, tuberculosis skin test.

Localized vs. Systemic Anaphylaxis

• Localized: Limited to a specific tissue or organ (e.g., allergic rhinitis).

• Systemic: Widespread, potentially life-threatening (e.g., anaphylactic shock).

Desensitization and Allergy Shots

• Desensitization involves repeated exposure to small amounts of allergen to reduce sensitivity.

• Allergy shots stimulate production of blocking antibodies (IgG).

Examples and Applications

• Transfusion reactions: Type II hypersensitivity.

• Post-streptococcal glomerulonephritis: Type III hypersensitivity.

• Graft rejection: Type IV hypersensitivity.

• Multiple sclerosis: Example of Type IV autoimmune disease.

HIV/AIDS

Virus Structure and Replication

HIV is a retrovirus that infects CD4+ T cells, leading to immune deficiency. Its replication involves reverse transcription and integration into host DNA.

• HIV replication cycle: Attachment, fusion, reverse transcription, integration, transcription, assembly, and budding.

Clinical AIDS vs. Latent State

• Latent state: Virus present but not actively causing symptoms; CD4+ count higher.

• Clinical AIDS: Marked by low CD4+ count and presence of AIDS-defining illnesses.

Transmission and Diagnosis

• Transmission: Blood, sexual contact, mother-to-child.

• Diagnosis: ELISA, Western blot, PCR; PCR is most sensitive and can detect infection soonest.

Vaccines and Immunological Assays

Types of Vaccines

• Toxoid vaccines: Inactivated toxins.

• Acellular vaccines: Contain purified components.

• Recombinant vaccines: Produced using genetic engineering.

• DNA/mRNA vaccines: Use genetic material to induce immunity.

Whole Agent Vaccines

• Attenuated: Live but weakened organisms.

• Inactivated: Killed organisms.

Antibody Function and ELISA

• Agglutination: Antibodies cause clumping of antigens, used to determine antibody titer.

• Indirect ELISA: Detects antibodies in patient serum using enzyme-linked secondary antibodies.

Control of Microbial Growth

Definitions

• Sterilization: Complete destruction of all microorganisms.

• Disinfection: Elimination of most pathogens (not spores).

• Antisepsis: Disinfection of living tissue.

• Degerming: Removal of microbes from a limited area.

• Bacteriostatic: Inhibits growth.

• Bactericidal: Kills bacteria.

• Asepsis: Absence of pathogens.

Moist Heat Methods

• Boiling: Disinfects, not sterilizes.

• Autoclaving: Sterilizes using pressurized steam.

• Pasteurization: Reduces microbial load, does not sterilize.

Other Methods

• Dry heat, filtration, low temperature, osmotic pressure, radiation.

Types of Disinfectants

• Phenols, bisphenols, alcohols, halogens, oxidizing agents, surfactants, heavy metals, aldehydes, gaseous agents.

Factors Affecting Chemical Efficacy

• Concentration, time, temperature, presence of organic matter, microbial characteristics.

Order of Microbial Resistance

Microorganism	Resistance Level
Prions	Highest
Bacterial spores	High
Mycobacteria	Moderate
Non-enveloped viruses	Moderate
Fungi	Low
Vegetative bacteria	Lowest

Antimicrobial Drugs

Definitions

• Antibiotic: Substance that inhibits or kills microorganisms.

• Spectrum of activity: Range of organisms affected.

• Broad-spectrum antibiotics: Effective against many types.

Mechanisms of Action

• Inhibitors of cell wall synthesis: e.g., penicillins.

• Inhibitors of protein synthesis: e.g., tetracyclines.

• Inhibitors of nucleic acid synthesis: e.g., quinolones.

• Inhibitors of essential metabolic pathways: e.g., sulfonamides.

Drug Resistance Mechanisms

• Decreased permeability, activation of drug pumps, change in drug binding site, use of alternate metabolic pathway.

Types of Antimicrobial Drugs

Drug Type	Example	Target
Anti-fungal	Ketoconazole	Fungal cell membrane
Anti-protozoan	Quinine derivatives	Protozoan metabolism
Anti-viral	AZT (Zidovudine)	Viral reverse transcriptase

Responsible Use of Antibiotics

• Prevents resistance, preserves efficacy.

Biotechnology and Recombinant DNA

Restriction Enzymes and Vectors

• Restriction endonucleases: Cut DNA at specific sequences.

• T4 ligase: Joins DNA fragments.

• Vector: DNA molecule used to carry foreign genetic material into a cell.

Transformation Methods

• Chemical transformation: Uses chemicals to induce uptake of DNA.

• Electroporation: Uses electrical pulses.

PCR and Its Components

• PCR (Polymerase Chain Reaction): Amplifies DNA for diagnostics and forensics.

• Taq DNA polymerase: Heat-stable enzyme for DNA synthesis.

• ssDNA primers: Short DNA sequences that initiate replication.

• Denaturation step: DNA strands are separated by heat.

Environmental and Applied Microbiology

Nitrogen Cycle

• Ammonification: Conversion of organic nitrogen to ammonia.

• Nitrification: Conversion of ammonia to nitrites/nitrates.

• Denitrification: Conversion of nitrates to nitrogen gas.

• Nitrogen fixation: Conversion of atmospheric nitrogen to ammonia.

Sewage Treatment

• Primary treatment: Removal of solids.

• Secondary treatment: Biological degradation.

• Disinfection: Elimination of pathogens.

Types of Waste Treatment

• Sewage treatment plants, septic tanks, wetlands systems.

Microorganisms as Weapons

Bacillus anthracis (Anthrax)

• Types: Cutaneous, gastrointestinal, inhalation.

• Habitat: Soil, animal products.

Advantages and Disadvantages of Bioweapons

• High lethality, ease of dissemination, but difficult to control and poses ethical concerns.

Yersinia pestis (Plague)

• Types: Bubonic, pneumonic.

• Transmission: Fleas (bubonic), airborne (pneumonic).

Smallpox Virus (Variola)

• Transmission: Respiratory droplets.

• Incubation period: 7-17 days.

• Vaccine: Vaccinia virus used for immunization.

Disease Progression and Control

• Incubation, major signs, fatality rate, and use of vaccines for prevention.

Table: Comparison of Bioweapon Agents

Agent	Type	Transmission	Control
Bacillus anthracis	Bacteria	Contact, inhalation	Antibiotics, vaccine
Yersinia pestis	Bacteria	Fleas, airborne	Antibiotics, isolation
Variola virus	Virus	Respiratory droplets	Vaccination

Additional info: These notes expand on the brief questions by providing definitions, mechanisms, and examples for each topic, ensuring a self-contained study guide for exam preparation.