Microbiology Exam 1 Flashcards by Erin groat

Define Prokaryotic

organisms without a true nucleus (on the other hand, eukaryotes have a true nucleus enclosed in a nuclear membrane)

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Define Nosocomial Pathogen

organism which causes infection, originating from a hospital

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Define Iatrogenic Pathogen

organism which causes infection that arises from health care intervention

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Define Occasional Opportunistic Pathogen

an organsim which causes infection because of a weaken immune system

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Define Normal Flora

the mixture of organisms regularly found at any anatomical site (the bacteria that naturally live in our body)

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What are the benifits of Normal Flora?

prevents colonization of pathogens
antagonize other bacteria (prevents growth of potentially harmful bacteria)
stimulates the production of antibodies

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What are the human responses to microbial invasion?

Phagocytosis
inflammation
immune response (T and B cells)

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Microorganisms respond to human response with:

capsule formation- gelatinous material surrounding bacterial cell wall, can protect cell from phagocytosis. (considered a virulence factor)
enzyme production
toxin production
biofilm production- a microbial community that usually forms a slimy layer on the surface

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Factors Influencing Microbial Growth

moisture (culture medium and incubators)
pH (culture medium)
temperature (incubators, most at 35-37 degrees C)
oxygen (atmosphere)
nutrition (culture medium)

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Define Obligate Aerobe

Organisms which require oxygen to grow

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Define Microaerophile

Organism which requires oxygen in low concentrations to grow

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Define Obligate Anaerobe

organisms that grow in the absence of oxygen

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Define Facultative Anaerobe

organisms which can grow with or without oxygen

growth rate is higher in the prescence of oxygen

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Define Aerotolerant Anaerobe

organism which only grows anaerobically, but continues growing in the prescence of oxygen

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Growth Phases

match the letter to the phase and explain

A. Lag- bacteria are adapting to environment, cannot divide but are preparing

B. Exponential Phase (or Log Phase)- period of cell dividing at a constant rate

C. Stationary Phase- occurs because something has limited growth (ex. depleation of an essential nutrient). New cell production = death of old cells

D. Death Phase- bacteria run out of nutrients an die

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Define Selective Media

A culture medium designed to suppress the growth of unwanted microorganisms and encourage the growth of desired ones (ex. MacConkey)

physical conditions of the media can be adjusted (such as pH and temperature) for the growth of certain organisms

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Define Nutritive Media

Medium which supports the growth of most organisms (ex. Blood Agar)

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Define Differential Media

A solid culture media that makes it easier to distinguish colonies of the desired organism

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What kind of agar is this?

Primary Ingredients?

Differential/Selective/ Enrichment/ Isolation?

Organisms?

Special Notes?

Agar: Chocolate Agar

Ingredients: 2% hemoglobin or IsoVitalex

Enrichment

Fastidious Organisms (Neiseria gonorrhoeae)

* essentially the same as sheep blood agar except the red blood cells are lysed which provides essential nutrients for fastidious organisms

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What kind of agar is this?

Primary Ingredients?

Differential/Selective/ Enrichment/ Isolation?

Organisms?

Special Notes?

Agar: Blood Agar

Ingredients: 5% sheeps blood

Enrichment/Differential

Nonfastidious organism

Hemolysis (alpha, betam gamma)

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What kind of agar is this?

Primary Ingredients?

Differential/Selective/ Enrichment/ Isolation?

Organisms?

Special Notes?

Agar: Phenylethyl alchohol (PEA)

Ingredients: nutrients

Selective, Isolation

Aerobic gram positive

Anaerobic gram negative bacilli and gram positive cocci

inhibits gram negative organisms

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What kind of agar is this?

Primary Ingredients?

Differential/Selective/ Enrichment/ Isolation?

Organisms?

Special Notes?

Agar: MacConkey

Ingredients: peptose base with lactose, crystal violet, bile salts, pH indicator

Selective, Differential, and Isolation

Enteric Bacilli

Seperates organisms based on lactose fermentation

Inhibits Gram positive organisms

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Which bacteria are lactose + and which are lactose negative?

The baceria on the left are lactose positive because the colonies are pink

The bacteria on the right are lactose negative because the colonies are clear/white

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What type of hemolysis is this?

Explain why

Alpha hemolysis on blood agar

Blood cells are only partially lysed and produce a greenish color around the colony

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What kind of hemolysis is this? Explain why

Beta hemolysis on blood agar Blood cells are completly lysed around the colony.

What kind of hemolysis is this? Explain why

Gamma hemolysis on blood agar There was no lysing of red blood cells

What is the purpose of Thioglycollate Broth and Schaedlers Agar? What are the ingredients?

To grown anaerobic bacteria pancreatic digestion of casein, soy broth, and glucose

Define Colonization

microbial organisms living in concert either harmlessly, symbiotically, or harmfully with a human host

# Define Disinfection

using an agent to destroy or inhibit microorganisms that may cause disease (but not there spores)

# Define Fomite

any inanimate object that may be contaminated with disease causing microorganisms and can therefore serve to transmit disease

# Define Isolation

preparing a microorganism specimen in such a way as to grow a colony from a single species for further identification or study

# Define Propagation

growth or spread of microorganisms

# Define Reservoir

The origin of the etiological agent or laction from which it dimmeminates (ex. water, food, insects, animals, other humans)

# Define Sterilization

a process by which all forms of microbial life and bacterial spores are killed

# Define Endotoxin

a component of gram negative bacterial cellular structure which can have devistating effects on the body's metobolism, released when cells are destroyed

# Define Exotoxin

common to gram positive bacteria, produced and released by living cells. Target specific hosts.

# Define Vector

Any living organism that transmitts an etiological agent.

# Define Virulence Factor

factors which increase the degree of pathogenicity or disease- producing abiltiys of microorganisms.

List Common Ways to Classify Bacteria

gram stain morphology biochemical characteristics site of clinical recovery antimicrobial susceptibility

List the Steps of the Gram Stain

fix microorganism to slide 1. Crystal violet: primary stain 2. Grams Iodine: mordent 3. Wash (alcohol, acetone): decolorizor 4. Saffranin: safranin

The pink organisms are\_\_\_\_\_\_\_ Gram +/-. The purple/blue organism are\_\_\_\_\_\_\_\_ Gram +/-.

Pink: Gram negative Purple/blue: Gram positive

Gram Stain and Morphology

Gram negative rod ex. *Escherechia coli*

Gram Stain and Morphology

Gram positive cocci ex. *Staphylococcus aureus*

Gram Stain and Morphology

Gram negatice cocci ex. *Neisseria gonorrhoeae*

Which type of bacteria ferment lactose? Example?

gram negative rods E. coli

Which gram negative organism DOES NOT ferment glucose or other sugars?

*Pseudomonas aeruginosa*

Give an example of a gram positive cocci that produces catalase.

Staphylococcus

Give an example of a bacteria that produces the enzyme coagulase.

*Staphylococcus aureus*

Give an example of a gram negative cocci that produces the enzyme oxidase.

Neisseria species

Are organisms recovered from blood and CSF clinically significant?

Yes

Is S. aureus recovered from respiratory specimens clinically significant?

Is S. aureaus recoved from a wound clinically significant?

Yes

Is E.coli recovered from a stool culture clinically significant?

Is E. coli recovered from urine or blood clinically significant?

Yes

What is happening in this picture?

_Antimicrobial suceptibility_- tests for bacterial sensitivity to antibiotics. - should always be performed on pure culture - certain organisms can be classified according to their susceptibility profiles - Ex. Methicillin resistant S. aureus (MRSA) - Vancomycin resistant Enterociccus (VRE)

What causes Gram positive organisms to retain the crystal violet dye?

thick peptidoglycan cell walls with numerous teichoic acid cross-linkages low permeability of decolorizer low lipid content

# Define Light microscopy

also called brightfield microscopy, uses light passing through a specimen and a series of lenses to magnify the specimen visually

What is this and what does it do?

_Objective lense_- the lens closest to the specimen usually 4X, 10X, 40X, and 100X (oil immersion)

What is the formula for total magnification?

magnification of objective x magnification of ocular - the ocular usually is 10X

# Define ocular lens

The lens closet to the eye which usually has a magnification of 10X

# Define resolution

the extent to which detail in the magnified object is maintained (sharpness, focus)

# Define contrast

the ability of the specimen to stand out from the background, staining improves and so does reducing the diameter of the aperture diaphram (but this will reduce resolution)

Label the diagram

What are the key diffrences between Prokaryotic and Eukaryotic cells?

**Prokaryotes** - no nucleus or membrane bound organells - always unicellular - DNA is circular - 70s ribosomes - no cytoskeleton - motility by flagellum - cell division by binary fission - always asexual reproduction **Eukaryotes** - often multicellular - true nucleus and membrane bound organelles - linear DNA - 80s ribosomes - always has cytoskeleton - cell division by mitosis/meiosis - reproduce sexually or aesexually

How are the quantities of bacteria expressed in the lab report?

rare, few, moderate, many 1+, 2+, ect

What is it important to give the quantity on a report?

It helps to correlate smear results with the amount of growth observed in the culture.

What color should phagocytes or white blood cells appear?

Pink or gram negative

Name 2 causes for an organism to appear gram variable.

antibiotic treatment old age autolytic enzymes

Gram stain morphology of *Staphylococcus aureus*.

Gram positive cocci in clusters