Comprehensive Study Notes: Microbe-Human Interactions, Immunity, Microbiome, and Parasitology

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Microbes interact with human hosts in various ways, influencing health and disease. Understanding these interactions is fundamental to microbiology.

Three significant interactions: Symbiosis (mutualism, commensalism, parasitism), pathogenicity, and opportunism.
Five phases of infectious disease: Contact and adherence (to host structures), colonization, invasion, infection, and exit.
Portals of entry: Routes by which microbes enter the host (e.g., skin, respiratory tract, gastrointestinal tract).
Microbial evasion of phagocytosis: Mechanisms such as capsule formation, antigenic variation, and secretion of anti-phagocytic factors.
Direct and indirect causes of tissue damage and disease: Toxins, immune response, and cell lysis.

Definition of signs vs. symptoms: Signs are objective evidence of disease (e.g., fever), while symptoms are subjective experiences (e.g., pain).
Stages of clinical infection: Incubation, prodromal, acute, convalescent, and resolution phases.
Patterns of infection: Localized, systemic, focal, mixed, and sequelae; classified by timeframes (acute vs. chronic).
Nosocomial infection: Infections acquired in healthcare settings (HAIs).
Definition of epidemiology: The study of disease distribution and determinants in populations.
Patterns of infectious disease occurrence: Endemic (constant presence), sporadic (occasional), epidemic (sudden increase), pandemic (global spread).

Innate immunity provides the first line of defense against pathogens, offering nonspecific protection.

Definition of immunity and susceptibility: Immunity is resistance to disease; susceptibility is vulnerability to infection.
Types of immunity: Innate (nonspecific) and adaptive (specific).
Three lines of defense:
- 1st line: Physical barriers (skin, mucous membranes).
- 2nd line: Internal cells and chemicals (phagocytes, inflammation, fever, antimicrobial proteins).
- 3rd line: Adaptive immune response (lymphocytes, antibodies).
Hallmarks and process of inflammation: Redness, heat, swelling, pain; involves vasodilation, increased permeability, and migration of immune cells.
Phagocytosis: Process by which phagocytes engulf and destroy pathogens; includes chemotaxis, adherence, ingestion, digestion.
Diapedesis: Movement of leukocytes out of blood vessels into tissues.
Interferon: Proteins produced in response to viral infection, inhibiting viral replication.
Complement system: Group of proteins that enhance immune responses, promote phagocytosis, and lyse pathogens.

Adaptive immunity is characterized by specificity and memory, involving lymphocytes and antibodies.

Immunocompetence and antigen: Immunocompetence is the ability to mount an immune response; antigens are substances that elicit immune responses.
Lymphocytes: B cells (bone marrow origin) and T cells (thymus origin); responsible for humoral and cell-mediated immunity.
Major histocompatibility complex (MHC): MHC I (all nucleated cells) and MHC II (antigen-presenting cells); present antigens to T cells.
Main roles of T and B cells: T cells mediate cellular immunity; B cells produce antibodies.
Superantigens: Potent antigens that can cause excessive immune activation, leading to toxic shock syndrome.
Primary and secondary immune responses: Primary response is slower and less robust; secondary response is faster and stronger due to memory cells.
Types of immunity:
- Natural immunity: Acquired through infection or maternal antibodies.
- Artificial immunity: Acquired through vaccination or antibody therapy.
- Active immunity: Body produces its own antibodies.
- Passive immunity: Antibodies are transferred from another source.

Hypersensitivity refers to exaggerated immune responses that can damage host tissues.

Four classes of hypersensitivity: Type I (immediate, allergy), Type II (cytotoxic), Type III (immune complex), Type IV (delayed, cell-mediated).
Development of allergies: Involves sensitization and subsequent exposure to allergens.
ABO and Rh blood groups: Important in transfusion medicine; incompatibility can cause hemolytic reactions.
Autoimmune responses: Immune system attacks self-antigens, leading to diseases like lupus and rheumatoid arthritis.
Immunodeficiency: Hypo-immunity; inability to mount adequate immune responses (e.g., HIV/AIDS).

Definition and benefits: Vaccines stimulate immunity, provide herd immunity, and prevent disease outbreaks.
Types of vaccines: Live attenuated, inactivated, subunit, toxoid, conjugate.
Characteristics of effective vaccines: Safety, long-lasting protection, minimal side effects.

The human microbiome consists of all microorganisms living in and on the body, playing crucial roles in health and disease.

Definition: Microbiota refers to the community of microbes; microbiome includes their genetic material.
Distribution: Microbes inhabit skin, gut, mouth, and other body sites.
Normal functions: Digestion, vitamin synthesis, immune modulation, protection against pathogens.
Development through life: Microbiome composition changes from birth to old age.
Dysbiosis: Imbalance in microbiome linked to diseases (e.g., obesity, diabetes, inflammatory bowel disease).
Prebiotics and probiotics: Prebiotics are substances that promote beneficial microbes; probiotics are live beneficial microbes.

Parasitology studies organisms that live on or in a host, causing harm. Protists and helminths are major groups of parasites affecting humans.

Groups of eukaryotic parasites: Protozoa, helminths (worms), arthropods (insects, ticks).
Definitions:
- Endoparasite: Lives inside the host.
- Ectoparasite: Lives on the host surface.
- Obligate: Must live as a parasite.
- Facultative: Can live independently.
- Free-living: Not parasitic.
- Direct life cycle: No intermediate host.
- Indirect life cycle: Requires intermediate host.
- Definitive host: Where parasite matures.
- Intermediate host: Temporary host for development.
- Reservoir: Source of infection.
Major groups of protozoan parasites: Amoeboid, flagellated, ciliated, apicomplexans (sporozoans).
Protozoan parasites (examples):
- Entamoeba histolytica: Causes amoebic dysentery; symptoms include diarrhea, abdominal pain.
- Trichomonas vaginalis: Causes trichomoniasis; symptoms include vaginal discharge, irritation.
- Giardia intestinalis: Causes giardiasis; symptoms include diarrhea, cramps.
- Trypanosoma brucei: Causes African sleeping sickness; symptoms include fever, neurological issues.
- Trypanosoma cruzi: Causes Chagas disease; symptoms include fever, swelling, chronic heart issues.
- Plasmodium: Causes malaria; symptoms include fever, chills, anemia.
- Toxoplasma gondii: Causes toxoplasmosis; symptoms include flu-like illness, risk to fetus.

Includes stages such as trophozoite (active feeding stage) and cyst (dormant stage).
Transmission often involves contaminated water, food, or vectors (e.g., mosquitoes for Plasmodium).