Final Lab Practical Flashcards
why is coccidioides immitis considered to be a dimorphic fungus?
It can grow as yeast or as mold depending on conditions
what is the difference between mold and yeast (macro and micro)?
yeast are creamy looking, moist, large and oval
mold are not creamy or moist
What are the growth differences between fungus and bacteria?
fungi-grow slower, at a lower temperature, and lower pH
what is the difference between vegetative hyphae and aerial hyphae?
Vegetative- grow down or into agar
aerial- grow above agar surface
what is the difference between sporangiospores and conidiospores?
spor- spores grow inside of a sack
conid- spores at the end of hyphae
how are molds identified in the laboratory?
macroscopic and microscopic appearance
Define bacteriophage
lytic
plaque
- virus that infects only bacteria
- lyses or bursting of the host cell
- area of clearing representing a virus blowing up a bacteria
what is the purpose of making dilutions of the T-4 virus?
you need a countable plate of plaques
Define obligate intracellular parasite
lytic cycle
- organisms that can only grow inside another living host cell
- cycle in which virus infects and then bursts their host once the appropriate number of viruses have been synthesized, killing the host cell
How does a medium used for bacterial growth differ from media used for bacteriophage growth?
the virus uses the bacteria on the media to grow/infect. ordinary agar/broth but bacteria is used as host cell
Differentiate between staphyloccocus and streptococcus by the catalase test
staph-positive, bubbles
strep-negative, no bubbles
what is the principle in the catalase and coagulase tests, what is the media used for each?
cat- does bacteria produce catalase enzyme, H2O2 (bubbles)
coag-does bacteria produce coagulase enzyme, rabbit plasma (white clumps)
calculate the titer of phage in the original sample given teh numbe of plaques and dilution of the plate.
what is the unit??
plaque count X dilution factor X sample amount = PFU’s/ml of sample
PFU’s/ml
differentiate between the two species of Staphylococcus by the coagulase test and reaction on mannitol salt agar
BE ABLE TO SPELL!!
Staphylococcus aureus- coagulase (+), yellow salt agar (+)
Staphylococcus epidermidis- coagulase (-), no change in media (-)
How is mannitol salt agar both a selective and differential media?
selective because of high salt and differential because of mannitol fermentation (if positive, bacteria will produce acid, which will change the pH of media, and change the color of media)
Determine species of Micrococcus by pigmentation or nitrate test result. BE ABLE TO SPELL
Micrococcus roseus- pink hue, (+) nitrate test (red at first, or no red after zinc)
Micrococcus luteus- yellow hue, (-) nitrate test(no color at first, red after zinc)
What is the gram result, morphology, and arrangement of staphylococcus and micrococcus?
gram (+), cocci, in clusters
Where are staphylococcus and micrococcus found in the body?
skin and mucous membranes
define carrier
MRSA
nosocomial
- a person who harbors a pathogen but exhibits no symptoms
- methylin resistant staphylococcus aureus
- health-care acquired disease
name two substances that staphylococcus aureus produces to cause disease.
- coagulase enzyme
2. catalase enzyme
when do staphylococcus epidermidis and micrococcus cause disease?
they opportunistic pathogens
describe the difference between the types of hemolysis.
alpha-bruised
beta-lysed, clearing
gamma-no change
why do you use the streak-stab method for blood agar inoculations?
let’s you see hemolysis better
State the atmosphere used to grow streptococcus.
candle-jar, they are microaerophiles
Differentiate the colony appearance of staphylococcus and streptococcus
staph-pigmented, convex, opaque, larger
strep-translucent, semi-opaque
which enzyme helps differentiate all staphylococci from streptococci
catalase
How did Lancefield divide the beta-hemolytic streptococci into groups?
c polysaccharide extracted from cell walls.
what is the species name of Lancefield group A streptococci?
group B?
- pyogenes
- agalactiae
Which test is used on alpha streptococcus, what are the results?
beta streptococcus?
alpha-optochin sensitivity-streptococcus mitis is resistant, streptococcus pneumoniae is sensitive
beta-bacitracin sensitivity- group C streptococcus is resistant, streptococcus pyogenes is sensitive
how is enterococcus different from other alpha hemolytic streptococcus?
enterococcus faecalis is the only one that is bile esculin positive, it is resistant to all sensitivity tests.
where is enterococcus normally found in the body?
gastrointestinal tract
Explain VRE
viridans streptococci
- vancomysin resistant enterococcus
- other alpha hemolytic streptococci other than streptococcus pneumoniae
name the organism that causes the following diseases:
- community-acquired pneumoniae
- dental cavities
- neonatal septicemia
- strep throat
- urinary tract infection
- streptococcus pneumoniae
- viridans streptococci
- Group B strep
- Group A strep
- Enterococcus
what are the two major groups of gram (-) rods and what are the common characteristics of each group?
enterobacteriaceae-gram (-), ferment glucose, oxidase (-)
non “”- gram (-) bacilli, no ferment glucose, oxidase (+)
which carbohydrate is used to determine whether a gram negative rod is a “nonfermenter’ or “enterobaceriaceae”?
glucose
what carbohydrates are in the Kliger Iron Agar media?
KI agar contains glucose and lactose
what carohydrate is in MacConkey agar?
lactose
Why is MacConkey agar considered to be selective and differential media?
selects using bile salts and crystal violet, inhibits gram (+) growth, differential with lactose fermentation.
what is an “enteric” organism?
normally part of normal flora of intestinal tract
How are culture media designed to detect if a bacteria can produce a specific enzyme?
substrates for the enzyme are incorporated into culture medium along with an indicator system to detect products.
what is the purpose of the Durham tube in the carbohydrate fermentation tubes?
detect gas formation
name the specific tests that are part of the IMViC test?
indole, methyl red, voges-proskauer, citrate
name three Enterobacteriaceae notmally found in the gi tract
escherichia coli
enterobacter arogenes
proteus vulgaris
Name two Enterobacteriaceae that are major pathogens and state the disease that each causes.
Salmonella-gastroenteritis and typhoid fever
Shigella-bacterial dysentery
Name one of many commercial test systems used to identify Gram (-) rods in clinical labs.
Enterotube, AP120E, Micro ID
Explain how CNA and MacConkey agar aid in the identification of bacteria in a mixed unknown.
CNA-selective for gram (+) and differential for hemolysis
MacConkey- selective for gram (-), differential for lactose fermentation
what does bacteria that grow on MacConkey and can fermet lactose look like?
Hot pink colonies
what type of organism grows on macConkey agar?
Gram (-)
what ingredient in the MacConkey agar will differentiate the organisms growing on the agar?
lactose
what type of organism grows on CNA?
gram (+)
How does the CNA medium inhibit the growth of gram negative rods?
It has narrow spectrum antibiotics in it to inhibit gram negative growth
What ingredient in the CNA media allows differentiation of the organisms growing on the agar?
blood
why is the CNA media incubated in the a candle jar?
microaerophilic
why is a cotton swab used to obtain the sample from the original broth?
its a mixed culture and so it ensure we get both bacteria
why is T. soy agar used to grow the “stock cultures”?
neutral media that sustains growth of all bacteria
Why do you need to develop TWO flow charts in order to identify your unknown organisms?
we have two unknowns, we need a key for both of them.
