Chapter 16: Host Microbe Interaction

The Anatomical Barriers as Ecosystems

Mutualism, Commensalism, & Parasitism

Mutualism

is an association in which both partners benefit e.g. some bacteria in the large intestine synthesize vitamin K and certain B vitamins that are in then available for our body to absorb

Commensalism

is an association in which one partner benefits but the other remains unharmed e.g. our skin microbiota

Parasitism

is an association in which one organism, the parasite, benefits at the expense of the other.

Pathogens are considered this

Normal Microbiota

is the group of microorganisms routinely found growing on the body of healthy individuals

Microbiome

community of normal microbiota

microbiome

Babies begin acquiring this during delivery and feeding.

The compositions of this in a baby changes overtime, as it encounters various foods, on pets, on other humans, and in the environmental establish themselves

Colonization

refers to the establishment and growth of a microbe in a particular environment

Infection

a microbe with a parasitic relationship with the host

Subclinical

symptoms either do not appear or are mild enough to go unnoticed

Infectious Disease

an infection that results in disease

Primary Pathogen

causes disease in otherwise healthy individuals

Opportunistic Pathogens

causes disease only when the body’s innate or adaptive defenses are compromised

Virulence

refers to the degree of pathogenicity of an organism

Communicable or Contagious diseases

spread from one host to another; ease of spread partly reflects

Infectious dose

the number of microbes necessary to establish an infection (the lower the the amount the easier it is to establish an infection)

1. incubation period

2. prodromal period

3. illness

4. convalescence

5. carriers

The progression of an infectious disease includes these stages

Incubation Period

interval between entrance of a pathogen into a susceptible host and the onset of illness caused by that pathogen

Prodromal Period

period of early, vague symptoms indicating the onset of a disease

Illness

period during which the person experiences signs and symptoms

Carriers

some people harbor an infectious agent for months or years and continue to spread the pathogen, even though they appear healthy

Acute, Chronic, or Latent

Infections can be

Acute

characterized by symptoms that develop quickly but last only a short time

(e.g. strep throat)

Chronic

develop slowly and last for months or years (e.g. tuberculosis)

Latent

infection in which the infectious agent is present but not causing symptoms (e.g. cold sores) → infections can be localized or systemic

Exotoxins

heat-liable, immunogenic, and potent

A-B toxins

the toxins mediated by the A subunit'; the binding to specific cells is mediated by the B subunit

Membrane-Damaging Toxins

Disrupt cell membranes either by forming pores or removing the polar head group on phospholipids in the membrane (include hemolysins, pore-forming toxins, and phospholipases

Superantigens

stimulate an abnormally high number of TH cells, causing a massive release of cytokines (a “cytokine storm”) that may lead to organ failure, circulatory collapse, and death

Endotoxin

is lipopolysaccharide (LPS), the molecule that makes up the outer layer of the outer membrane of the gram-negative cell wall. In small amounts it causes a normal immune response; in high amounts it can lead to shock and possible death. (heat stable)