L14.Pathogens

Pathogens

• Microorganisms: Tiny living things such as bacteria, viruses, and fungi.

  • Some microorganisms are beneficial, e.g., compost breakdown.

  • Pathogens: Microorganisms that cause diseases.

• Spread of Diseases: Pathogens cause a variety of infections (e.g., tuberculosis, meningitis, pneumonia).

  • Spread through the chain of infection.

Chain of Infection

• Definition: Route that a pathogen travels from an infected host to a new host.

  • Starts with the infectious agent located on/in the carrier.

  • Carrier: Source of infection that may or may not show illness.

• Process:

  1. Infectious agent leaves the carrier's body.

  2. Transmission to a new host via:

     • Direct contact (e.g., handshake).

     • Airborne droplets (via coughs and sneezes).

     • Surface contact (e.g., contaminated surfaces).

     • Vector-borne transmission (via insect bites).

  3. Penetration: Infectious agent breaches host's barriers (e.g., skin, mucous membranes).

  4. Host becomes a new carrier.

• Key components of the chain: Infectious agent, host, suitable environment.

  • A healthy immune system attacks pathogens; a compromised host may offer suitable conditions for infection.

Susceptible Hosts

• Definitions:

  • Susceptible host: Person unable to effectively fight infection.

  • Commonly includes elderly, children, or compromised individuals (e.g., those undergoing cancer treatment).

Infection Control

• Healthcare professionals use infection control procedures and medications to combat pathogens.

  • Antimicrobial agents kill or inhibit the growth of microorganisms.

Bacteria

• Pathogenic Bacteria: Associated with illnesses like pneumonia, UTIs, and gonorrhea.

  • Single-celled organisms reliant on host for nutrients.

  • Release toxins that cause illness.

  • Most infections are treated with antimicrobial drugs.

• Bacterial Classification:

  • Identified using a Gram stain technique:

    • Gram-positive: Stains deeply (e.g., vibrant purple).

    • Gram-negative: Stains lightly (e.g., not as colored).

• Bacterial Shapes: Key shapes include:

  • Cocci (spherical): Streptococci (chains), Staphylococci (clusters).

  • Bacilli (rod-shaped): Cause diseases like tuberculosis.

  • Vibrios (comma-shaped), Spirilla (rigid corkscrews).

• Case Study: George's infection identified as Bacillus anthracis (anthrax) through Gram staining of lesions.

Viruses

• Characteristics: Non-cellular entities that require a host to replicate.

  • Examples: Coronavirus, influenza, HIV.

• Viral Infection Process:

  1. Attach to and inject viral genome into host cell.

  2. Replicate viral components.

  3. Host cell bursts, releasing new viruses.

• Rapid reproduction leads to quick infection spread (e.g., cold or flu).

  • Some viruses may remain latent within the host.

Fungi and Protozoa

• Fungi: Infect individuals with weakened immune systems.

  • Target hair, nails, skin, and mucous membranes.

• Protozoa: Single-celled microorganisms that can cause diseases (e.g., gastroenteritis, malaria).

  • Transmission often through insect bites or contaminated food/water.