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Microbio Lab exam
Microbio Lab Final
| Question | Answer |
|---|---|
| Why is oil used at higher magnifications? | It increases the microscope's resolution because it doesn't allow as much of the light to bend. (it has a high refractive index) |
| What is the diameter of a typical red blood cell? | 6-8 micrometers |
| What does TSA stand for? | Tryptic Soy Agar |
| Define complex media. | Media that DO NOT have a precise chemical composition. (ex: brain heart infusion broth) |
| Define defined media. | Media that DOES have a precise chemical composition. (ex: M9 which contains specific molar amounts of salts and sugars) |
| What type of media is TSA? | Complex. |
| What does it mean that TSA is a "complete medium"? | It's suitable for the growth of most aerobic microorganisms. |
| What information should be on your labeled agar plate? | 1) Name 2) date 3) lab section 4) name of organism 5) incubation temperature |
| What do K. rhizophila colonies look like on a TSA plate? | small, opaque bright yellow |
| What do E. coli colonies look like on a TSA plate? | large, round translucent tan |
| What is the purpose of tryptic soy broth? | Broth is used to propagate one type of bacteria quickly |
| What is the purpose to tryptic soy slant agar? | Good for storage (doesn't take up as much space as a TSA plate) |
| What is the purpose of tryptic soy deep agar? | Used to determine a bacteria's motility, and a little to determine whether or not it can grow anaerobically |
| What is the purpose of tryptic soy plate agar? | used for bacteria colony growth and isolation, often used for identification or for further testing. |
| What type of tryptic soy agar (broth, slant, deep, or plate) would be most useful for rapid disease diagnosis and why? | Plate, because it would isolate bacteria types into colonies which you could then use for identification and further testing if needed. |
| Which organism is responsible for MRSA? What other diseases can it cause? | methicillin-resistant staphylococcus aureus; pneumonia and meningitis. |
| What year was the gram stain discovered and by whom? | 1882, Hans Christian Gram |
| What is the primary stain in gram staining and how does it work? | Crystal violet - permeates cell walls |
| What is the second solution in gram staining, and what does it do? | Gram's Iodine - it's the MORDANT, meaning it chemically modifies crystal violet to form CV-IODINE COMPLEXES that are insoluble in water, but NOT alcohol |
| What is the third solution in gram staining, and what does it do? | Ethanol - decolorizes gram negative cell walls of CV-iodine complexes |
| What is the secondary stain in gram staining, and how does it work? | Pink saffranin - it counterstains the gram negative cell walls (without altering the darker purple color of the gram positives) |
| Which is better to use for gram staining - an old culture or a fresh culture? | FRESH - old can stain weird. |
| How long should Gram's Crystal Violet sit on the slide? | 60 seconds |
| Hoe long should Gram's Iodine sit on the slide? | 60 seconds |
| How long should decolorization take place? | 15-30 seconds |
| How long should Gram's Safranin sit on the slide? | 60 seconds |
| What type of paper should you blot (NOT WIPE) the slide with after gram staining has taken place? | Bibulous paper |
| What is the gram staining and cell shape of E.coli? | gram (-) bacillus |
| What is the gram staining and cell shape of Staphylococcus epidermidis? | gram (+) cocci |
| What is the gram staining and cell shape of Bacillus subtilis? | gram (+) bacillus |
| True or False: Staphylococcus infections are most effectively transmitted through the air. | FALSE - through direct contact or fomites |
| What type of agar (complex or defined) is Nutrient Agar (NA)? | Complex |
| What type of agar (complex or defined) is Sabouraud Dextrose Agar (SDA)? | Complex selective |
| Nutrient Agar (NA) is used for the growth of what type of organisms? | non-fastidious (not picky) |
| Sabouraud Dextrose Agar (SDA) is used for what? | for the isolation of dermatophytes |
| What are some unique features of Sabouraud Dextrose Agar (SDA)? | 1) It's pH is 5.6 (promotes growth of certain fungi, while inhibiting growth of some bacteria. 2) It contains some antibiotics (that make it even more selective for fungi) STILL, some fungi WON'T grow on SDA, and some bacteria WILL. |
| Magnification = _____ x _____ | Objective, eye piece |
| What is antibiosis? | Biological interaction between two or more organisms that is detrimental to at least ONE of them |
| What does HAI stand for? | Healthcare Associated Infection |
| How long should handwashing take? | 40-60 secs |
| What is transcient microbiota? | microbiota thats only on the body for hours/months, and cannot persist in the body |
| Which is more effective: paper towels or air dryers? | PAPER TOWELS |
| What is BLAST? | Basic Local Alignment Search Tool |
| What is an e-value? | How closely the protein sequence you enter into BLAST matches the best match provided by BLAST. If its 1, than they are identical. If it's O, than they are completely separate. |
| What is a protein domain? | Part of a protein sequence and structure that can evolve, function, and exist independently of the rest of the protein chain. |
| What does MecA stand for? | Gene responsible for methicillin resistance MRSA. |
| What does PBP stand for? | Penicillin binding protein; allows b-lactam drugs like penicillin to bind to PBP to disrupt the cell walls of bacteria |
| What is the relationship between PBP2A and MecA? | presence of PBP2A in a bacterial cell wall causes methicillin resistance. |
| What disease is Staphylococcus saprophyticus most commonly associated with? | UTIs |
| What disease is Streptococcus pyogenes most commonly associated with? | strep throat |
| What is distinctive about Staph aureus's colony morphology? | Golden colored colonies |
| What is the hemolysis of S. aureus? | beta |
| What do the colonies of s. pyogenes look like? | white |
| What are the catalase and coagulase test results for s. aureus? | positive and positive; almost all others are negative for both, except s. saprohyticus, which is positive for catalase) |
| What does a catalase test test for? what is a postive result? | Test for the presence of the catalase enzyme in the microorganism using hydrogen peroxide. Postive = bubbling. |
| What does a coagulase test test for? what is a positive result? | Test for the organism's possession of coagulase, which allows it to convert fibriogen to fibrin. Positive = macroscopic clumping. (only staph bacteria that are positive are S. aureus) |
| What is special about Mannitol Salt agar (MSA)? | Both selective AND differential: - high salt concentration (selective for gram POSITIVE bacteria) -Differential in that it distinguishes manitol fermentors from not |
| What does a yellow color (change from pinkish) on Mannitol Salt agar indicate? | Gram+, mannitol fermenting. |
| Where is S aureus normal flora? | Various parts of the skin and NASAL PASSAGES |
| What is blood agar (BA) used for? | growth of fastidious organisms and to detect hemolysis |
| What is chocolate agar (chA) used for? | (Type of blood agar in which the blood cells have been lysed by boiling.) It's used for the growth of REALLY fastidious respiratory bacteria, like Haemophilus influenzae |
| What are the distinguishing features of Staphylococcus aureus? | Beta hemolysis, golden colonies, positive coagulase test |
| What is hemolysin? | Exotoxin produced by bacteria that causes lysis of RBCs. Tested for on Blood agar. |
| What is penicillinase? | Enzyme produced by some bacteria to resist Beta lactam drugs |
| What is the cut off for indication of infection in urine? | 100,000 cfu/mL |
| What is an oxidase test? How is it performed? What is a positive result? | Determines if a bacteria produces cytochrome c oxidases. Postive = BLACK coloration within 10-30 secs. |
| What is significant about Mueller-Hinton agar (MHA)? | used for antibiotic susceptibility testing |
| What antibiotics disrupt the cell membrane? | Polymxin B and amphotericin B (the fungi one) ONLY WORKS ON GRAM NEGATIVE BACTERIA (very NARROW) |
| What antibiotics disrupt the cell wall? | Penicillin, bacitracin, vancomycin (fairly narrow) |
| What antibiotics inhibit protein synthesis? | Aminoglycosides, chloramphenicol, and tetracycline) (BROAD SPECTRUM, especially tetracycline) |
| What antibiotics inhibit nucleic acid synthesis? | Rifampin, AZT, quinolones (narrowish) |
| What antibiotics inhibit metabolic pathways? | SULFA drugs (narrowish) |
| What is the most broad spectrum drug we tested? | Tetracycline |
| What is the most narrow spectrum drug we tested? | Tie between polymxin B (only gram negative) and vancomyocin (only gram positive) |
| What is Pyelonephritis? | kidney infection |
| Enterotube: what does a positive GLUCOSE test look like? what does it mean? | Positive: Yellow (neg-> red) Indicates: Bacteria is able to ferment glucose. Color change is the result of pH shift by production of acid during fermentation. |
| Enterotube: what does a positive LYSINE test look like? what does it mean? | Positive: purple (neg-> yellow) Indicates: Bacteria can decarboxylate lysine, making it more alkaline |
| Enterotube: what does a positive ORNITHINE test look like? what does it mean? | Positive: purple (neg->yellow) Indicates: Bacteria can decarboxylate ornithine, making it more alkaline |
| Enterotube: what does a positive H2S test look like? what does it mean? | Positive: Black (neg->beige) Indicates: Bacteria can reduce sulfur-containing compounds |
| Enterotube: what does a positive INDOLE test look like? what does it mean? | Positive: Red (neg->colorless) Indicates: Bacteria produce indole by metabolizing tryptophan (because they possess tryptophanase) |
| Enterotube: what does a positive ADONITOL, LACTOSE, ARABINOSE, and SORBITAL test look like? what does it mean? | Positive: yellow (neg->red) Indicates: Bacteria can ferment these, producing acid (leading to change of color to yellow) |
| Enterotube: what does a positive VP test look like? what does it mean? | Positive: Red (neg->colorless) Indicates: Bacteria uses ACETOIN as an intermediate in the production of butylene glycol from glucose fermentation |
| Enterotube: what does a positive DULCITOL test look like? what does it mean? | Positive: yellow (neg->green) Indicates: Bacteria can ferment dulcitol |
| Enterotube: what does a positive PHENYLALANINE test look like? what does it mean? | Positive: black-smoky gray (neg->green) Indicates: Bacteria can deaminate PA to pyruvic acid |
| Enterotube: what does a positive UREA test look like? what does it mean? | Positive: Pink (neg->beige) Indicates: Bacteria possesses urease, and can hydrolyze urea to ammonia (making everything more ALKALINE) |
| Enterotube: what does a positive CITRATE test look like? what does it mean? | Positive: blue (neg->green) Indicates: Bacteria can utilize citrate as a source of carbon |
| What is unique about MacConkey Agar? | -contains bile salts and crystal violet which INHIBIT GRAM-POSITIVE bacteria -contains only LACTOSE -differentiates lactose fermentation ability |
| What does a red colony on MacConkey Agar indicate? What about a colorless? | Red: CAN ferment lactose Colorless: can't |
| What is unique about Eosin methylene blue (EMB) agar? | -contains eosin Y and methylene blue pH which INHIBIT GRAM+ bacteria -contains both LACTOSE and SUCROSE |
| What are the possible results of EMB, and what do they indicate? | Metallic green: can ferment lactose AND sucrose quickly (i.e. E.coli) Dark pink: can slowly ferment JUST lactose Colorless/light pink: none |
| What is unique about Hektoen enteric (HE) agar? | -designed to SELECTIVELY IDENTIFY SALMONELLA AND SHIGELLA -high bile salt concentration INHIBIT GRAM POSITIVE, AND SOME NONPATHOGENIC COLIFORMS |
| What are the possible results of HE, and what do they indicate? | Yellow-orange (plus potentially an opaque haze around the colonies): can ferment LACTOSE, SUCROSE, and SALICIN Salmon-yellow: Ferments SALICIN ONLY Light green-translucent: can't ferment any (i.e. salmonella and shigella) Black precipitate: SALMONELLA |
| What are some of the purposes of the normal microbiota in the gut? | 1) prevent attachment of pathogens 2) vitamin synthesis |
| What is ELISA? How does it work | Enzyme linked immunosorbent assays; Uses antibody binding to identify pathogens harboring particular epitopes |
| True or False: ELISA can be used to identify either antigens or antibodies found in a patient specimen. | TRUE |
Created by:
E.brown009
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