Host Pathogen Interactions

Flashcards covering key vocabulary and concepts related to host-pathogen interactions, bacterial virulence factors, and modes of transmission.

Saprophytism

Environmental bacteria that thrive on dead organic matter and live independently of a host; typically non-pathogenic but may express pathogenicity in immunocompromised hosts.

Mutualism

A symbiotic relationship in which both the host and the bacterium benefit. Disruption may lead to dysbiosis.

Commensalism

One organism (microorganism) benefits from the interaction, while the other (Host) is not affected.

Parasitism

A relationship where one organism benefits at the expense of the host, causing symptoms such as fever, fatigue, or rashes.

Opportunistic Bacteria

Usually harmless in healthy individuals but can cause disease when host defenses are compromised.

Normal Flora

Microorganisms that reside on or within the human body in a symbiotic manner.

Resident Flora

Fixed-type of bacteria, non-pathogenic, inhabit specific body sites permanently.

Transient Flora

Temporarily present on the body, non-pathogenic or potentially pathogenic, confines: skin's superficial layers OR mucosal surfaces (hours, days or weeks).

Pathogenicity

The qualitative ability of a microorganism to cause disease in a susceptible individual.

Virulence

The degree of pathogenicity, or how severe the disease is. The minimum infectious dose (ID 50 ) to cause disease (quantitative aspect)

Pathogenicity Factors

Enable infection initiation in the host and examples include adhesins, fimbriae, pili, and surface proteins.

Virulence Factors

Determine the severity and progression of disease and examples include toxins (exotoxins, endotoxins), capsules, and enzymes.

Bacterial Infectivity

Factors produced by bacteria that enable infection (e.g., toxins, adhesins).

Host Resistance

Host defenses against infection (immune response, barriers).

Phagocytosis Inhibition

Capsule: masking cellular surface structures (receptors); Preventing Acidification of the Phagosome; Resisting killing by Lysosomal Chemicals; Resisting phagocytic destruction: killing the phagocyte

Bacterial Adhesins

Adhesins extend out from the cell surface and interact with host cell to cause Bacterial colonization.

Toxins

Exotoxins or Endotoxins. Toxico-genesis: Production of the toxin with or without prior colonization by the bacterium.

Exotoxins

Proteins secreted from cell, high toxicity and highly antigenic.

Endotoxins

Part of cell (lipopolysaccharide) that fragments off, low toxicity and poorly antigenic.

Hyaluronidase

digest hyaluronic acid "glue" keeps tissues and joints lubricated.

Collagenase

break down collagen fibers = structural protein to help bacteria invade deeper tissues.

Coagulase & kinase

fibrinogen → fibrin to form or dissolve blood clots.

Innate Host Defenses

Nonspecific defenses including physical and chemical barriers.

Acquired Host Defenses

Specific defenses developed uniquely for each microbe through specialized white blood cells.

Vertical Transmission

Transmission is from parent to offspring via the ovum, sperm, placenta, or milk

Horizontal Transmission

Disease is spread through a population from one infected individual to another

Endemic Disease

Constantly present in a certain population or region, relatively low spread.

Epidemic Disease

Sudden increase in cases spreading through a large population like a country

Pandemic Disease

Sudden increase in cases spreading through several countries, continents, or the whole world.

Community-Acquired Infection

Acquired in the general community (home, schools, public places)

Nosocomial Infection

Acquired in healthcare settings (hospitals, clinics, nursing homes)