BMS 501 Practical Study Guide

how do you calculate total magnification of an object being observed under a light microscope?

objective magnification (10x, 40x, 100x) X ocular magnification (10x)

orange

fine focus

orange

course focus

orange

coaxial stage controls

orange

neck

orange

observation tube

orange

eyepiece

where is the ocular lens located in a microscope

in the eyepiece

orange

nosepiece

orange

objective lens

orange

stage

orange

condenser lens

orange

iris diaphragm

orange

light source

Which is properly written?

Escherichia coli or Escherichia coli

Escherichia coli

How do you shorten an organisms name? Use Escherichia coli as an example

E. coli

simple stain

coloring cells to see shapes

Gram stains

differentially coloring cells to see shapes and determine Gram class

Endospore stains

differentially coloring to see if the species makes spores

what type of cell wall do Gram-negative cells have?

thin peptidoglycan layer

what type of cell wall do Gram-positive cells have?

thick peptidoglycan layer

Staphylococci morphology

cocci in grape-like clusters

Bacilli morphology

rods, spore-forming

Clostridia

Rods, spore formers

Enterobacteriaceae (E. coli, klebsiella, salmonella, shigella) morphology

rods

mycobacteria morphology

rods, weakly gram positive

acid fast stain positive

what color is Gram-negative in a gram stain

pink

what color is Gram-positive in a gram stain

purple

first step of gram staining

put crystal violet (primary stain) on the slide for 1 minute

second step of gram staining

put Gram’s iodine (mordant) on the slide for 1 minute

third step of gram staining

put acetone alcohol (decolorizer) on the slide for less than 5 seconds

fourth step of gram staining

put safranin (Counterstain) on the slide for 1 minute

why do Gram-negative bacteria result in a pink appearance in a Gram stain

because they have a thin peptidoglycan layer which allows for the decolorizer to get rid of the purple color from the crystal violet, then they get stained pink with the safranin

why do Gram-positive bacteria show up purple in a gram stain

because they have a thick peptidoglycan layer preventing the decolorizer from ridding the cells of the purple crystal violet stain

what plate is this

Mannitol Salt Agar (MSA)

is Mannitol Salt Agar (MSA) plates selective or differential

selective and differential

selective for Gram positive bacteria

differential for fermentation of the sugar mannitol using phenol red as an indicator

what does a positive MSA plate look like?

phenol red (pink color) turns yellow when mannitol salt is fermented

what does a negative MSA plate look like?

phenol red (pink color) remains red-orange in color due to the fact that mannitol sugar is not fermented

what plate is this

Nutrient Agar (NA)

is nutrient agar (NA) plates selective or differential

neither they allow growth of many organisms, does not exclude or distinguish

what plate is this?

Blood Agar Plate (BAP)

how can you differentiate between a Blood Agar Plate (BAP) and Mannitol Salt Agar (MSA) plate?

a MSA plate will appear reddish-pink and a BAP will have a darker red color

are blood agar plates (BAP) selective or differential

differential only

what does alpha hemolysis mean on a BAP

bacteria can partially breakdown blood

what result on a BAP plate is this

alpha hemolysis

what does beta hemolysis on a BAP mean

bacteria can completely breakdown blood

what result on a BAP plate is this

beta hemolysis

what does Gamma hemolysis on a BAP plate mean

bacteria cannot breakdown blood

what result on a BAP plate is this

gamma hemolysis

Are bile esculin slants (BES) selective or differential

selective and differential

selective for gram positive species due to bile salts

differentiates species by esculin hydrolysis

what result of a BES test is this

positive

it can hydrolyze esculin

what result of a BES test is this

negative

it cannot hydrolyze esculin

what test is this?

Bile Esculin Slant (BES)

is a catalase test selective or differential?

differential based on the bacteria’s ability to produce the enzyme catalase

is this catalase result positive or negative?

negative

is this catalase result positive or negative?

positive

what does a positive catalase test result mean?

it can produce catalase

does Streptococcus agalactiae grow on MSA plates

no it doesn’t grow

what is aseptic technique?

methods of working free of microbial contamination

why is aseptic technique important?

prevents culture/specimen contamination

prevents contamination of yourself/others/environment

what does aseptic technique include

safely dispensing culture media

flame-sterilizing instruments

proper labeling, handling, and storing

practicing correct hand hygiene and workspace disinfection

what is selective media

only permits the growth of certain type of bacteria

inhibits other types of bacteria in many ways including: salt content, high/low pH, antibiotics

what is differential media

allows visually differentiation between two or more kinds of bacteria due to chemical reactions in the media

more than one type of bacteria can grow on the plate

How do you properly label plates and tubes

initials/lab section/type of media/what is on it/date

where do you label a plate

on the bottom, not the lid

what is the first step to a quadrant streak

flame an inoculating loop, wait for it to cool, collect a loopful of the bacteria and spread it across 1/4th of the plate

what is the second step of a four quadrant streak

flame the inoculating loop, wait for it to cool and then drag some bacteria from the first quadrant and streak it into another 1/4th of the plate

what is the third step of a quadrant streak?

flame the inoculating loop and wait for it to cool, drag some bacteria from quadrant 2 and spread it onto another 1/4th of the plate

what is the fourth step of a quadrant streak?

flame the inoculating loop, wait for it to cool and spread some bacteria from quadrant 3 into the final 1/4th of the plate and spread it

acid-fast staining

stains thick, waxy lipid walls

what does a pink mean in an acid-fast stain

acid fast positive

what does a blue result in an acid-fast stain mean

counterstained aka negative

diagnosis and treatment of Candida

microscopic analysis of vaginal discharge reveals budding yeast or yeast in hyphal form

yeast can also be identified by culture methods

first-line treatments: antifungal azole drugs

how many tapeworms infect humans

6 tapeworms

ex: Taenia saginata from beef and Diphyllobothrium latum from fish

Bill Nye discovered a new bacterial species that he named named Sciencius guyus!  After growing a culture overnight at 37°C, he spread 3 CFU plates, 100uL on each. The 10^-3 plate has 3149 colonies; the 10^-4 plate has 229 colonies; the 10^-5 plate has 15 colonies. What is the CFU/mL of the culture?

2.29 × 10⁷ CFU/mL

An E. coli outbreak was traced by epidemiologists back to a batch of infected lettuce.  Approximately 20,000 heads of lettuce had been sold from the crop, and there were 127 reported illnesses and 6 reported deaths.  Laboratory testing on the lettuce revealed an average number of 50 cells of E. coli bacteria present on a given plant.  Approximate the ID₅₀ and LD₅₀ of the E. coli strain, assuming each head of lettuce was eaten by 1 person. Use Scientific notation

ID50 = 3.9 x 10³ cells

LD50 = 8.3 x 10⁴ cells

ID50: 10,000 (half of population)/127 (amount of people sick) = 78.74 × 50 (amount of cells) = 3,937 cells = 3.9 × 10³ cells

LD50: 10,000 (half of population)/6 (amount of people dead) = 1,666.66 × 50 (amount of cells) = 83,333 cells = 8.3 x 10⁴ cells

how are O₂ requirements tested

thioglycolate tubes

obligate aerobe

needs oxygen to live, breaks down sugars using it

absolute dependence on oxygen use in metabolism

can effectively manage reactive oxygen species

obligate anaerobe

dies in presence of oxygen (doesn’t use it, can’t detoxify it)

has no dependence on oxygen use in metabolism → not used

cannot effectively manage reactive oxygen species

microaerophile

can only stand oxygen in low concentrations

uses small amounts of oxygen in metabolism

can effectively manage reactive oxygen species but only in small amounts

aerotolerant anaerobe

doesn’t use oxygen, but doesn’t die when exposed to it (Can detoxify it!)

oxygen is not used in metabolism, but can live in the presence of it

can effectively manage reactive oxygen species

facultative anaerobe

prefers oxygen, but can do anaerobic respiration and detoxify oxygen when needed

prefers using oxygen for metabolism but can survive without it

can effectively manage reactive oxygen species

where does Bordetella pertussis infect

lungs

whooping cough

where does mycobacterium tuberculosis infect

lungs

where does mycoplasma pneumoniae infect

lungs

what are common ventilator-associated pneumonias

Acinetobacter baumannii, Pseudomonas aeruginosa, and MRSA

where does Borrelia burgdorferi infect

blood and lymph

lyme disease

where does Treponema pallidum infect

blood and lymph

syphilis

where does Yersinia pestis infect

blood and lymph

plague

where does Staphylococcus aureus infect

skin

staph infections → wound infection, scalded skin syndrome, CAUTIs, pneumonia, sepsis

where does Propionibacterium acnes infect

skin

where does Helicobacter pylori infect

stomach

ulcers

where does Clostridioides difficile infect

large intestine

where does Salmonella species infect

large intestine

extreme thermophiles

grow in 65-120 degrees C

thermophiles

grow in 40-75 degrees C

mesophiles

grow in 10-50 degrees C

human body temperature

psychrotrophs

grow in 0 to 30 degrees C

psychrophiles

grow in -20 to 10 degrees C

Are Triple Sugar Iron (TSI) slants selective or differential

differential based on ability to ferment lactose, sucrose and glucose