Lab Practical Flashcards
What is purpose of the Bacterial contamination lab?
Methods to prevent contamination
How do you calculate total magnification?
objective lens X ocular lens = total magnification
Giardia trophozite?
Protozoa
Amoeba?
Protozoa
Plasmodium falciparum trophozites?
Protozoa
Trypanosoma
Protozoa
Candida Albicans
yeast (fungi)
Rhizopus
mold (fungi)
Aspergillus
mold (fungi)
purpose of Aseptic transfers lab
minimize contamination to yourself, others, environment, source culture, and media
Inoculating tools?
- Loop 2. Bunsen burner
purpose of simple stains lab?
cells are stained with a colored dye to make them/structures more visible
Morphology/Arrangement of:
- Staphylococcus epidermis
- Micrococcus luteus
- Bacillus megaterium
- Rhodospirillium
- cluster cocci
- cluster cocci
- string bacilli
- single spirulum
Purpose of Gram stain lab
to distinguish and identify gram (=) or (-) bacteria
List the steps of a gram stain
- A heat-fixed smear is covered w/crystal violet
- CV is washed off with distilled water & iodine applied
- decolorization with alcohol
- Alcohol rinsed and safranin applied
Gram stain results
Gram (-)= reddish pink
Gram (+) = purple
Gram positive or negative?
1. Staphylococcus epidermis
2 Escherichia coli
3.Bacillus megaterium
- (+)
- (-)
- (+)
Purpose of acid fast stain
differential stain; to identify members of mycobacterium
what is the stain used in acid fast stain
carbolfuchsin(+) counterstain is methylene blue or brilliant green
Why is carbolfuchsin used in an acid fast stain?
waxy wall repels typical aqueous stains
What are representative bacteria for acid fast staining?
mycobacteria
What are representative bacteria for capsule staining?
Streptococcus pneumonia
what is the purpose of capsule staining?
differential stain; allows detection of extracellular capsule
what types of stains are used in capsule staining?
Congo red or nigrosin
What is the purpose of endospore staining?
differential stain; allows detection of presence and location of endospore
What types of stains are used in endospore staining?
malachite green to stain endospore; safranin for counterstain
Why is endospore staining different?
Endospore is made of keratin and resistant to staining
What are representative bacteria for endospore staining?
Bacillus and Clostridium
What is the purpose of the blood agar lab?
isolation and cultivation of fastidious bacteria and differentiate based on hemolytic characteristics
define selective media
enhances isolation procedure by inhibiting growth of some organisms, encouraging others
define differential media
an indicator to expose differences b/w organisms
streak plate method
used to isolate individual organisms from a mixed culture
alpha hemolysis
partial destruction of red blood cells w/ greenish discoloration
beta hemolysis
complete destruction of RBC; clearing on plate
gamma hemolysis
nonhemolysis; simple growth, no change in medium
purpose of mannitol salt agar lab
selects for bacteria that can tolerate high salt concentration
Staphylococcus aureus
yellow growth on mannitol salt agar plate
Maconkey agar purpose
to isolate and differentiate members of Enterbacteriacae based on ability to ferment lactose
poor growth on Mac plate
inhibited by CV and/or bile. Gram (+)
growth/reddish color Mac plate
produces acid from lactose fermentation. Gram (-) or coliform
Purpose of Eosin Methylene Blue lab
isolation of fecal coliforms
Eosin Methylene Blue lab: poor growth
inhibited by eosin methylene blue; gram (+)
Eosin Methylene Blue lab: good growth
not inhibited by eosin methylene blue; gram (-)
Eosin Methylene Blue lab: dark colored growth
lactose/sucrose fermentation
Eosin Methylene Blue lab: pink colored growth
little lactose fermentation
Purpose of catalase test lab
to identify organisms that produce the enzyme catalase
Anaerobic respiration
reduce inorganic molecules such as nitrate or sulfate
Aerobic respiration
reduce oxygen to water or other compounds
fermentation
production of nitrogen gas
what is the reagent used in catalase test?
hydrogen peroxide
purpose of oxidase test
to identify bacteria containing enzyme cytochrome c oxidase
Purpose of Nitrate reduction test
differentiates Enterbacteriacae from other Gram (-) rods that either do not reduce nitrate or nitrite or reduce it beyond
Nitrate Reduction positive reaction:
Red color after adding reagents A&B= nitrate reduction to nitrite
Nitrate Reduction reaction after adding zinc:
red color after zinc= no nitrate reduction
no color change after zinc:
nitrate reduction to nongaseous compound (+)
Purpose of Phenol Red Broth
to differentiate members of Enterbacteriacae from other gram neg rods
Phenol Red Broth: yellow color
acid production from fermentation of a carbohydrate lowers pH and turns broth yellow
Phenol Red Broth: Bubble in durham tube
gas produced
Phenol Red Broth: pink color
degradation of peptones/alkaline end products
Purpose of Methyl Red Voges-Proskauer test
to differentiate members of Enterbacteriacae from other gram neg rods
MR positive
red color= mixed acid fermentation
MR negative
no color change= no mixed acid fermentation
VP positive
red color=acetoin production
VP negative
no color change= no acetoin production
MR reagent
Methyl red dye & alcohol
VP reagents
A(alpha naphthol/alcohol) & B(potassium hydroxide and water)
Purpose of Citrate test
to determine ability to use citrate as sole source of carbon
Why is citrate used?
to provide a means for enzyme citrate permaze to transport, but does not support citric acid cycle
Positive citrate test
Blue color= citrate utilized (+)
growth; no color change
citrate utilized (+)
No growth or color change
citrate not utilized (-)
Purpose of starch hydrolysis lab
to isolate and identify Gagenerella vaginalis & differentiate members of Corynebacterium, Bacillus, Clostridium….etc…
Positive starch hydrolysis
clearing around growth; Amylase present
Negative starch hydrolysis
no clearing; Amaylase not present
reagent in starch hydrolysis test
iodine
why is iodine used in starch hydrolysis?
to detect presence or absence of starch
Purpose of Urea Hydrolysis lab
to differentiate based on ability to hydrolyze urea w/enzyme ureas
Positive Urea Hydrolysis
pink= rapid urea hydrolysis; strong urease production
Negative Urea Hydrolysis
orange/yellow= no urea hydrolysis; no urease production
Purpose od Gelatin Hydrolysis lab
to determineability to produce gelitanase
positive gelatin
gelatin is a liquid= gelatinase present
negative gelatin
gelatin is a solid= no gelatinase present
Purpose of SIM lab
sulfur reduction, indole production, motility
Reagent used in SIM
Kovac’s reagent
Positive S. reaction
black in the medium; sulfur reduction
Negative S. reaction
no black; sulfur is not reduced
Positive I. reaction
Red in Kovac’s reagent layer; tryptophan is broken down into indole and pyruvate
Negative I. reaction
no color change in Kovac reagent layer; tryptophan is NOT broken down into indole and pyruvate
Positive M.
growth radiating from stab line
Negative M.
No growth radiating from stab line
Purpose of gel eletrophoresis
analyze DNA fragments and determine size of molecules
how does gel electrophoresis work?
charged molecules enter cell walls. molecules with a (-) charge move towards (+) electrode and vice-versa
what happens to smaller sized molecules?
quicker and easier migration
what happens when there is a greater amount of charge
faster migration
Purpose of ELISA
antibody measurement & detection of antibodies
Steps of ELISA
- Anitgen added to wells
- wash away unabsorbed material
- serum added & binds w/Ab present; wash
- substrate added
what occurs when the substrate is added?
substrate is peroxidase; converts peroxide to H2O + O2; which oxidizes aminosalidase (brown reaction); easily observed
what is the purpose of the antimicrobial susceptibility lab?
to measure the effectiveness of antibiotics
Which antibiotic creates the largest zone of inhibition?
Eyrthrmycin
How does penicillin work?
it inhibits the cross-linking of peptidoglycan in Gram + cell walls
Purpose of UV radiation Damage and repair lab
to measure decontamination of UV& ability to penetrate various objects
prolonged exposure to UV
distort DNA molecules & interfere with DNA replication and transcription
light repair/photoreactivation
DNA photolayse; monomerizes dimer & reverses original reaction
excision repair/dark repair
of enzymes involved; make DNA double stranded again
Taenia
Tapeworm
Ascaris
roundworm
Trichinella spiralis
roundworm
