MIC 141: Pathogenesis Pt. 1 (Adhesion, Colonization, and Invasion)

Colonization without disease (carrier)

Subclinical infection

Host-Microbe interactions

-Removal/destruction by host defenses

-Colonization without disease

-Replication and tissue damage

A clinical infectious disease involves (presence + diseased state)?

Replication and tissue damage

Persistence of an organism in or on the host

Infection

Colonization or invasion of the host resulting in tissue damage (produces something; engages immune cells)

Infectious disease

The ability or potential of an organism to cause disease

Pathogenicity

The degree or intensity of an organism's pathogenicity (how severe the disease is)

Virulence

What do virulence factors contribute to?

-Invasion

-Evasion or subversion of host defenses

-Tissue damage

A microorganism that causes disease even in healthy hosts

Primary pathogen

A microorganism that normally causes disease only in hosts that are compromised in some way (ex. immunocompromised, puncture wounds)

Opportunistic pathogen

Host defense factors

-Immune status

-Co-evolution of hosts and pathogens

What are factors involved in immune status?

-Immunocompromised

-Immunosuppressive therapy

What are some things that lead to an individual being immunocompromised?

-Genetic defects

-Other diseases (HIV)

-Stress levels

What is an example of co-evolution of host pathogens

-Malaria and sickle cell anemia

-Tuberculosis in asian vs. european populations

Routes of entry for pathogens

-Ingestion

-Inhalation

-Trauma (burns, stabbings, gun wounds)

-Needlestick

-Arthropod bite (ticks, dogs, mosquitoes)

-Sexual transmission

What are the five steps of infectious diseases?

Adherence, Replication, Invasion, Evasion of host defenses, Tissue damage

The first step for any infectious agent. Is a needed step to colonize host cells

Adherence

What are the two components of adherence?

Adhesins and Integrins

Microbial surface structures that attach to a host cell receptor

Adhesins

Host cell receptors that bind to microbial adhesins that are important for host cell function

Integrins

What are the three main types of adhesins?

-Pili (fimbriae)

-Non pili

-Bacterial capsules

Hair-like projections that are present on the surface of bacteria (mostly gram negative bacteria)

Pili (fimbriae)

Pili facilitate adherence of __ to the mucosal surface of the bladder

uropathogens

What are the special types of pili used for motility in Neisseria gonorrhoeae and Pseudomonas aeruginosa?

Type IV

Adhesins of Gram positive bacteria

Non-pili

An extracellular polysaccharide matrix

Bacteria capsules

What do Bacterial capsules do?

-Promote adherence to host cells

-Prevents phagocytosis

-Aids in adherence to other bacteria to form biofilms

Biofilms are especially a concern during joint and hearth valve replacement as they make it more difficult for __ to get in

Antibiotics

What are integrins typically comprised of?

Glycolipids or Glycoproteins

Determine host cell tropism

Integrins

The susceptibility of a host to infection by a microorganism (what animals are affected)

Host tropism

The cells or tissues of a host that support the growth of a particular microorganism (what tissues are infected within the body)

Tissue tropism

What do microbes typically have to do to cause infectious disease?

Replication

What are the sites of replication within a host?

-Extracellular growth

-Intracellular growth

Growth that occurs outside of host cells

Extracellular growth

Growth that occurs inside of host cells

Intracellular growths

Pathogens that can either grow on mucosal surfaces or within host cells

Facultative intracellular pathogens

What is an example of a facultative intracellular pathogen?

Salmonella enterica

When pathogens invade host cells, what are the strategies for survival and replication?

-Evasion of host defenses

-Source of nutrients

-Less competition

-Access to host cell machinery (replication of viruses)

Nutrients inside the host cell are essential for...?

Obligate intracellular pathogens (Chlamydia and Rickettsia)

Some pathogens exploit host __ mechanisms

Internalization

What are the host internalization mechanisms that pathogens exploit

-Phagocytosis by innate immune cells (neutrophils, dendritic cells, macrophages)

-Forced uptake into phagocytic cells

What bacterial pathogen uses both phagocytosis intake by immune cells and forced uptake into nonphagocytic cells

Salmonella enterica

Microorganisms that damage host cells must __, and __ new host cell

Escape, Invade

Viruses may __ from a host cell to acquire the cell membrane, or escape via __ of the host cell

Bud, Lysis

What bacteria exploit host cell proteins to propel themselves into adjacent healthy host cells (puncture)?

Listeria and Shigella