Medical Microbiology Test 1

What are the 4 concepts that make up medical microbiology

microbiology, immunology, clinical medicine, public health

Define microbiology

microbes that cause disease. (what? where? how?)

Define immunology

host responses to these microbes

Define clinical medicine

diagnosis and treatment of disease

define public health

methods for prevention of microbial infections

Describe infectious diseases in 1900

infectious diseases are the top 3 causes of death, including respiratory infections, diarrhea, and TB. Diptheria is at the bottom coming in at number 10.

describe infectious diseases in 2000

infectious diseases aren’t at the top of the list but they still make up 4 out of 10. lower respiratory diseases, diarrhoeal diseases, TB, and HIV/Aids.

describe infectious diseases in 2016

Gotten better but respiratory diseases, diarrhea diseases, and TB still make the list. TB deaths have been dropping throughout time

describe infectious diseases in 2019

TB has been dropped from the list. Lower respiratory diseases and diarrhea diseases continue dropping. If we were to add covid to the list, it would be number 3.

Describe current infectious diseases and their effect

while infectious diseases have been dropping over time, they still play an important role in health and disease. Lower income places have more deaths from infectious diseases compared to upper-middle income.

who was the first person to state that diseases could spread from an infected person to others in 430 BC

Thucydides

Who was the predecessor of the germ theory of disease. They stated “seed-like entities that transmit infection by direct or indirect contact over long distances in 1546

Girolamo Fracastoro

Who first observed microorganisms in the 1670s and was labeled the father of microbiology

Anton Van Leewenhoek

Who presented the final evidence against spontaneous generation with the swan-neck experiments in the 1860s

Louis Pasteur

Who identified the causative agents of anthrax, TB, and cholera using the mouse experiments in the 1880s

Robert Koch

What are the two domains that pathogens are known to be across

Bacteria and Eucarya. Also viruses, but they are acellular

What are the majority of infectious diseases caused by

bacterial and viral pathogens

Describe infectious diseases in developing countries

infectious diseases are higher in developing countries with parasitic infectious having a larger percentage than developed countries.

What is the difference between the human microbiota and the human microbiome

the human microbiota describes all the microbial organisms that live on the human body while the microbiome is all the genes that those microbes contain.

What do the healthy human body microbes look like

microbes that colonize the host and do not cause disease/harm under normal conditions

Can microbes be permanent or transient. And can environment and lifestyle change this?

They can be both permanent or transient. Yes environment and lifestyle can effect this, especially diet.

What do micorbes do?

They help promote a healthy immune system, protect against pathogens, and produce a variety of metabolites through fermentation

Where are microbes found

On all sites that come into coneact with the enviornment. Skin, mouth, respiratory tract, GI tract, anus, urogenital tract

What does a sterile site mean

A place in the body that does not contain any microbes. Like the blood, CSF, pleural fluid and bone, ETC.

What are passive defenses

Defenses that prevent entry of pathogens. These are barriers such as the skin, epithelial cells, and mucous.

What are active defenses

Defenses that destroy and/or eliminate pathogens. This is a broad category that can include enzymes, ciliated epithelial cells, and the cells of the immune system.

Describe a host

It is an organism that supports the growth of a microbe. Larger, multicellular organism. The patient/human

Describe a microbe

two small to be seen with the unaided eye. Can be cellular or acellular. And it is most commonly bacteria or a virus

WHat are the cellular microbes

bacteria, archea, protozoa, fungi, parasitic worms

What are the acellular microbes

viruses and prions

define commensalism

one organism benefits, the other is unaffected

define mutualism

both organsims benefit

define parasitism

one organism benefits, the other is harmed

what is an example of commensalism

the normal microbiota of the skin. The microbe gets food and a stable environment while the host gets nothing. This also describes the microbes that colonize the host

what is an example of mutualism

The microbiota of the GI tract. The microbe gets food and a stable environment, where the host gets vitamins, protection, and immune stimulation.This also describes microbes that colonize the host.

what is an example of parasitism

Pathogenic microbes, the ones that cause disease. All viruses and intracellular bacteria. The microbes get food and a protected environment to grow while we get damage to our cells or tissues. This also describes the microbes that infect the host.

abnormal state of the host(person); any condition where normal structures or functions are damaged or impaired

disease

describes the process of development of a disease

pathogenesis

any microbe that causes disease

pathogen

what determines the cause of the disease/infection

etiological agent

in ecological use, it is an organism that is in a parasitic symbiosis with another. in medical use, it is a disease causing protozoa and worms (endoparasitic)

parasite

Describe some infection characterisitcs

They are usually acute but can be chronic. They also usually lead to disease but don’t have to. When there is no overt disease it is called subclinical, asymptomatic, or an inapparent infection.

define signs

objective and measurable. Fever or temperature

define symptoms

subjective, felt or experienced. Headache or tired

define syndromes

collection of signs and symptoms that occur together.

Describe pathogen characteristics

not all microbes have the same ability to cause disease, even if they enter a normally sterile site

the capacity of a microbe to cause disease

pathogenicity

the extent or severity of disease caused

virulence

the ease at which a microbe can enter the sterile sites of the body

infectivity

characteristics of a microbe that allow it to cause disease

virulence factors

the spectrum of hosts that a microbe can replicate in

host range

presence of an organism in a person typically associated with overt disease. can cause disease in healthy individuals

obligate pathogen

organism requires predisposing factors to become disease-causing. typically causes disease in only immunocompromised individuals. organism may be present in a preson without causing overt disease.

opportunistic pathogens

What is the distribution of obligate/opportunisitc pathogens in bacteria

some obligate

many oppurtunistic

What is the distribution of obligate/opportunisitc pathogens in viruses

mostly obligate pathogens

What is the distribution of obligate/opportunisitc pathogens in fungi

a few obligate, mostly oppurtunistic

What is the distribution of obligate/opportunisitc pathogens in parasites

mostly obligate pathogens

What is the distribution of obligate/opportunisitc pathogens in prions

all obligate.

What factors determine if opportunistic pathogens cause disease

if the microbe has virulence factors

large population

microbe gains access to normally sterile sites

host immune system is weakened

what factors determine if opportunistic pathogens do not cause disease

if microbe lacks virulence factors

small population size

host barriers to invasion are intact

host immune system is strong

infectious established by microbes that come from the outside of the host

exogenous infections

What type of pathogens can be exogenous

ALL obligate pathogens

SOME opportunistic pathogens

infection established by microbes that normally colonize the host

endogenous infections

what type of pathogens can be endogenous

SOME opportunistic pathogens, only

What are the steps for the mechanism of pathogenesis

1. exposure and pathogen entry

2. tissue adhesion/attachment and infection

3. immune avoidance

4. damage to host tissues

5. exit/shedding of pathogen (for communicable diseases)

Some species have variability in production of virulence factors from one organism to another, leading to differences in disease and severity

What is the pathogenesis outline for vibrio cholera

pathogen enters the host cell, adherence to the host cell, extracellular growth, exotoxin production which contributes to cell and tissue damage. shedding of the pathogen from extracellular growth. Immune response tries to neutralize the damage

what is the pathogenesis outline for influenza A

pathogen enters host cell, adherence to host cell, penetration into host cell, intracellular growth, cell and tissue damage, shedding of pathogen. Immune response tries to neutralize the damage.

What is portal of entry

the way that mathogens can enter the body. pathogens typically have a sing POE

What are the three portal of entries

Mucous membranes, skin, parenteneal

describe the mucous membrane portal of entry

most common.

GI tract, respiratory tract, urogenital tract, conjunctivia

describe the skin portal of entry

where pathogens can get into the body through small lesions or cuts on the skin

describe parentneal portal of entry

where pathogens enter the body through injection

number of organisms (on average) needed to cause disease

infectious dose

number of organisms needed to cause disease in 50% of hosts infected

infectious dose 50

Describe specific adherence

Means that the pathogen can only adhere to a specific receptor, limiting the number of cells it can adhere to. This causes a narrow host range and tropism

describe a non-specific adherence

the pathogen can adhere to a receptor on multiple types of cells. Makes for a broad host range and tropism

the different cells and tissues in a body that can be infected

tropism

what adherence mechanism do viruses have

attachment proteins

what adherence mechanism do bacteria, fungi, and parasites have

adhesins

Where can extracellular pathogens be found

intersitial spaces, blood, lymph, and along epithelial surfaces

describe extracellular pathogens found in intersitial spaces, blood, lymph

not all pathogens can reproduce outside a host cell, but almost all pathogens have an extracellular stage in their life cycle

describe extracellular pathogens found in epithelial surfaces

Most bacteria, fungi, parasites. No viruses

who does penetration into host cell apply to

ALL viruses, MANY parasites, SOME bacteria, FEW fungi

Phagocytosis

bring in large cellular pathogens

endocytosis

bring in viruses and small cellular pathogens

membrane fusion

bring in enveloped viruses only

Describe membrane fusion

enveloped viruses only. spontaneously due to hydrophobic nature of lipid bilayer

describe endocytosis

triggered by virus binding to host cell. after endocytosis the viral genome still needs to gain access to the cytoplasm

what are the three ways the viral genome can gain access to the cytoplasm

membrane fusion: it fuses the membrane to get released into cytoplasm

injection: DNA/RNA is injected into the cytoplasm

lysis: the vesicle itself is broken down

what kind of pathogens are most frequently entered into the cell by phagocytosis

bacteria, fungi, parasites

this is triggered by pathogen binding

what kinds of cells can be infected by phagocytosis

only phagocytic cells, most commonly macrophages

What is required for survival inside phagocytic cells

virulence factors

Describe vesicular intracellular pathogens

grow and stay inside the vesicle

Bacteria, fungi, parasites. NO viruses

describe cytoplasmic intracellular pathogens

few bacteri and parasites, ALL viruses, NO fungi

Describe phagocytosis

a bacterium adheres to a phagocytic cell. The pseudopods (long arm things) then start to wrap around the bacterium until it is fully surrounded. The phagocytic cell then fuses with the lysosome to form the phagolysosome which aids in digestion.

Describe how different intracellular pathogens survive phagocytosis

some pathogens leave the vesicle and stay in the cytoplasmic, these are the cytoplasmic intracellular proteins

the vesicular intracellular pathogens can prevent the fusion of the phagosome with the lysosome. Others allow for the fusion but then block the process of digestion.

Describe localized infection without the invasion of tissue

the spread of a pathogen only occurs in restricted location at or near point of entry, without invading the tissues below. Applies to mostly extracellular cells

Describe how vibrio cholera is a localized infection without invasion

The microbes adhere to the surface of the epithilial cell and spread further along the surface but never into the cell or underlying tissues

describe how influenza A is a localized infection without invasion

The microbes adhere to the host and penetrate through the cell and grow inside there. This then kills the original cell and spreads to it’s neighboring cells.

Describe local invasion of tissues

The spread of the pathogen is still restricted in location but not confined to the outer layer of cells. Infection gets deeper into the tissues. This means that normal barriers of infection are breached (mainly extracellular pathogens) or circumvented (intracellular pathogens)