ch 11: Relationship Between Microbes and Humans

mutualism

A relationship in which the host and dependent both benefit

antagonism

A relationship in which two independent organisms work against one another

synergism

A relationship in which independent organisms work together for a common benefit

commensalism

A relationship in which the dependent benefits and the host sees no effect

parasitism

A relationship in which the dependent benefits and the host is harmed

antibiosis

An extreme example of a nonsymbiotic relationship in which one organism kills

Pathogenicity

the likelihood something will make you sick while, the ability for an organism to cause disease

virulence

is how sick it could make you, the degree of pathology that could be causes

virulence factors:

1. 1. fimbriae for attachment

2. 2. the ability to live intracellularly to evade the immune system

3. 3. Various means of immune suppression

4. 4. toxins to cause damage

5. 5. destructive enzymes to promote deeper infection

general tasks pathogens have to establish an infection:

• 1. get in

• 2. attach firmly

• 3. avoid host defenses

portal of entry

where a microbe must enter to cause disease

The more infectious the pathogen the lower the infectious dose

true

helps bacteria adhere to a host

fimbriae, pili, glycocalyx

helps viruses adhere to a host

capsid proteins, envelope, spikes

helps protozoa adhere to a host

cilia

adhesins

molecules on the ends of adhesive structures that bind to cell surface receptors on the host

how microbes avoid phagocytosis once inside the host:

1. 1. live intracellularly

2. 2. secrete enzymes to repel leukocytes

3. 3. capsules

gram negative bacteria produce ___ that are part of lipopolysaccharides

endotoxins

exoenzyme

a virulence factor that allows bacteria to promote deeper infection

exotoxin

a virulence factor that is secreted by a variety of bacteria and has specific effects on target cells

endotoxin

a virulence factor that is part of the outer membrane of gram negative bacteria and has systemic effects

superantigen

a virulence factor that causes damage by overstimulating the immune system

hyaluronidase

degrades skin structure

stages of infection cycle:

• 1. incubation

• 2. prodromal

• 3. acute

• 4. convalescent

incubation stage

no symptoms, but pathogen is multiplying

prodromal stage

generic symptoms appear (malaise, fatigue)

acute stage

most pronounced illness with specific signs and symptoms

convalescent stage

gradual return to health and strength

When are people likely to stop taking antibiotics prematurely?

convalescent stage

Nausea, back pain, blurred vision, are a sign or symptom?

symptom

Swelling & low blood pressure are a sign or symptom?

sign

reservoir

natural habitat of a pathogen

vehicle

an inanimate object that transmits disease

vector

a biting insect that transmits disease

disease reservoir

can be an environmental source such as soil or water

direct transmission

requires close physical proximity or actual contact

vertical spread

is only via sperm, egg, across the placenta, during birth, or via breast milk

horizontal spread

is spread of disease from one host to another through the population.

zoonotic spread

is spread of disease from a nonhuman animal to a human

A disease that spreads from host to another but does not do so easily is _____ but not _____

communicable, contagious

Which is not a common site for healthcare associated infections?

mouth

asymptomatic carrier

someone who has an infection with no signs or symptoms at any point

epidemic

a higher-than-expected number of cases of a disease in a given region

pandemic

is epidemic spread across continental boundaries

endemic

describes a relatively steady frequency of a disease in a given area over a long period of time

When does a human acquire most of their microbiome?

during birth and shortly after

You would likely find normal microbes everywhere but:

the bones

What types of microbes are part of the microbiome?

bacteria, viruses, fungi, protozoa

infectious dose

the minimum number of microbes required to make someone sick

leukopenia

an abnormal decrease of white blood cells

fomite

an inanimate object that can become contaminated with infectious agents

sequelae

Damage that persists long after recovery from infection, such as paralysis associated with polio

koch’s postulates

link a causative agent to a new disease