Lab quiz: Epidemiology & Isolation Techniques

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Epidemiology

the study of how microbes spread within a group or
population

Portal of entry

the way a microbe enters and infects a new host (Like an entranceway)

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idk how to get rid of it on mobile ❤

Portal of entry examples

• Direct contact

• Respiratory route

• Ingestion

• Vector

• Skin

• Gastrointestinal tract

Opportunistic pathogen

Acquired from another person or may have already been in or on that individual

Who is more likely to develop infections from opportunistic pathogens?

Immunosuppressed patients

Where is Staphylococcus aureus commonly found, and what can it cause?

It commonly occurs on human skin but can cause staph infections

Normal biota (flora)

Microbes found on our skin that are usually harmless and difficult to remove

Which microorganisms are examples of normal biota?

Staphylococcus epidermidis and Staphylococcus aureus

Transient organisms

Organisms found on the skin for a short periods of time but do not grow there

How do transient organisms usually get on the skin?

Through contact with contaminated surfaces

Are transient organisms easily removed from the skin?

yes

Are transient organisms easily removed from the skin?

Yes, some transient organisms can cause disease

Why don’t transient organisms stay on the body for long?

They have difficulty competing with established resident microbes and are eliminated by the immune system

Vector

A living organism that transmits disease

Biological Vector

An organism in which a parasite undergoes part of its life cycle before being transmitted to another organism

How do biological vectors transmit disease?

Directly, often through biting

What is an example of a biological vector?

The female Anopheles mosquito.

Mechanical Vector

An organism that transmits a parasite but is not part of its life cycle

How do mechanical vectors transmit disease?

Indirectly, by carrying disease organisms on their bodies

What are examples of mechanical vectors?

Fleas and ticks

What bacterium causes Tuberculosis?

Mycobacterium tuberculosis

What does the term “tubercle” mean?

Nodule or growth

When did Tuberculosis become a major problem?

During the Industrial Revolution

Who identified Mycobacterium tuberculosis and when?

Robert Koch in 1882

How long can it take for Tuberculosis to develop?

years

Can an infected person spread Mycobacterium tuberculosis before showing symptoms?

yes

What is Mycobacterium tuberculosis sensitive to?

Ultraviolet ray(ioli)s

Reservoir of Infection

An Object that allows a microbe to grow, reproduce, and maintain the ability to infect a new host

Fomite

n object that allows a microbe to survive and pass to a new host

How does soap help clean the skin?

It breaks down oils on the skin, allowing trapped bacteria to be washed away

What are micelles?

Spheres of lipids that form in aqueous solutions and help lift dirt and oils from the skin

What role does friction play in hand washing?

It physically removes emulsified skin oil and bacteria

What is an antiseptic?

A chemical that kills microbes

What are examples of antiseptics?

Hydrogen peroxide and triclosan.

Aseptic Technique

Handling microbes and materials in such a way that minimizes contamination

What does the aseptic technique prevent?

• prevents the microbes you are transferring from contaminating the work area or yourself

• prevents the microbes being transferred from getting contaminated 

Contamination

Presence or possible presence of microbes where they do not belong

Aseptic Technique examples:

wearing lab coats, hand washing, cleaning all work surfaces, using incinerators

Who developed many of the techniques used to isolate bacteria in pure cultures?

Robert Koch and his team

What is agar and where is it derived from?

Agar is a gelatin-like substance derived from seaweed

At what temperature does agar melt?

100 °C

At what temperature does agar solidify?

42–45 °C

Is agar considered a medium or an additive?

Agar is an additive

What purpose does agar serve in culturing bacteria?

It provides a solid surface for bacterial growth, allowing isolated colonies to form

What is a colony?

A clump of bacteria growing on a solid surface

Colony Forming Unit

The bacterial cell in a colony that arose from a single original cell

Every cell in the colony is _____ _____.

Genetically identical

What is the goal of isolating bacteria?

To obtain a pure culture

Pure cultures are needed to:

• Carrying out biochemical testing

• Determining antibiotic sensitivity

• Developing vaccines

• Determining nutritional requirements

• Studying organisms that cause disease

Are bacteria autotrophic or heterotrophic?

Heterotrophic

Where are bacteria grown in a laboratory setting?

On media

Growth media

Substrate for bacteria to grow in or upon

Complex media (undefined)

Media that use extracts from other organisms such as animals, plants, or fungi

What are the characteristics of complex media?

They are rich in nutrients and support a wide range of bacterial growth

What is an example of complex media?

Tryptic soy media

What does tryptic soy media contain?

Enzymatic digests of casein and soybean in undefined amounts

Chemically defined media

Media that contain pure organic and inorganic compounds added in exact, known amounts, with narrow range of bacteria growth

Enriched media

Media to which specific nutrients are added to support bacterial growth

What type of microbes does enriched media allow to grow?

Fastidious microbes

Fastidious microbes

those with complex nutritional requirements

What are examples of enriched media?

Blood agar and Brain-Heart Infusion (BHI) agar.

Name the media form

Agar plate

Name the media form

Broth

Name the media form

Agar slant

How is powdered media prepared?

It is dissolved in distilled water

What is an autoclave?

An instrument that sterilizes media using steam under pressure

What temperature does an autoclave reach during sterilization?

121 °C

What pressure does an autoclave use?

15 pounds per square inch

How long must materials be autoclaved to ensure sterilization?

20 minutes—to kill all bacteria, fungi, spores, and viruses