BIO 2440 Lab Final Exam Review PDF

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BIO 2440: Principles of Microbiology Lab Final Exam Review Section Four: Selective Media 1. Mannitol Salt Agar (MSA) a. How is MSA selective? What does it select for? selects for gram-positive halophiles high salt concentration differentiates mannitol fermenters b. What is the indicator used in MSA? phenol red c. What result indicates a positive? What does a positive result mean? positive – yellow growth positive for mannitol fermentation (Staphylococcus aureus) 2. MacConkey Agar (MAC) a. How is MAC selective? What does it select for? selective for gram-negative enteric bacterial species differentiates lactose fermenters b. What is the indicator used in MAC? neutral red c. What result indicates a positive? What does a positive result mean? positive – pink/red growth positive for lactose fermenters 3. Eosin Methylene Blue Agar (EMB) a. How is EMB selective? What does it select for? selective for gram-negative bacteria inhibit gram-positive growth differentiates weak/strong lactose fermenters b. What is the indicator used in EMB? Eosin Y Methylene Blue c. What result indicates a positive? What does a positive result mean? positive – dark purple or green metallic growth strong lactose fermenter; fecal coliform

d. What is a fecal coliform? enteric species present in the gut and feces gram-negative lactose fermenter

Section Five: Differential Tests 1. Phenol Red (PR) Fermentation Broth a. What is the indicator used in PR broth? Phenol red b. Between which types or species of bacteria does PR broth differentiate? gram-negative carbohydrate (usually glucose) fermenters and non-fermenters c. What result indicates a positive? What does a positive result mean? positive – yellow broth able to ferment glucose 2. Catalase Test a. What enzyme does this test for? catalase b. What function does this enzyme perform? neutralizes toxic oxygen metabolites (H2O2) cleaves hydrogen peroxide (dangerous to bacteria) c. Between which types or species of bacteria does the catalase test differentiate? catalase positive – micrococcus and staphylococcus catalase negative – streptococcus, enterococcus, lactococcus d. What result indicates a positive? What does a positive result mean? positive – bubbling (effervescence) organism produces catalase 3. Citrate Utilisation Test a. What is the indicator used in Simmons’ citrate agar? bromothymol blue b. What enzyme does this test for? citrate permease citrate lyase

c. What function does this enzyme perform? transport of citrate into the cell, hydrolysis of citrate into oxaloacetate and acetate d. Between which types or species of bacteria does the citrate utilisation test differentiate? members of the enterobacteriacaeae e. What result indicates a positive? What does a positive result mean? positive – blue agar organism able to use citrate as a carbon source and ammonium dihydrogen phosphate as the sole source of nitrogen 4. Bile Esculin Test a. What causes the color change in bile esculin agar? esculetin reaction with ferric ions b. What enzyme does this test for? esculinase c. What function does this enzyme perform? catalyze the hydrolysis of esculinase into esculetin and glucose d. Between which types or species of bacteria does the bile esculin test differentiate? Enterococcus faecalis and Group D Streptococci from non-group D Streptococci e. What result indicates a positive? What does a positive result mean? positive – more than half black organism produces esculinase 5. Indole Test a. What enzyme does this test for? tryptophanase b. What function does this enzyme perform? hydrolysis of tryptophan into indole and pyruvate c. Between which types or species of bacteria does the indole test differentiate? differentiate Enterobacteriaceae, especially E.coli, from Enterobacter, Klebsiella, Hafnia, and Serratia d. What result indicates a positive? What does a positive result mean? positive – cherry red layer when add Kovac’s reagent

organism is able to produce tryptophanase 6. Blood Agar a. What is the difference between alpha, beta, and gamma hemolysis? alpha – incomplete (greenish) beta – complete (clearance around colony) gamma – no effect b. Between which types or species of bacteria does blood agar differentiate? Differentiation within the genera Streptococcus, Enterococcus, and Aerococcus

Section Seven: Medical, Environmental, and Food Microbiology 1. What is the difference between a substance that is bacteriostatic and one that is bacteriocidal? bacteriostatic – inhibits the growth/reproduction bacteriocidal – kills the bacteria 2. What is a zone of inhibition? How is it interpreted? area in which growth is prevented on susceptible bacteria based on size and standards 3. What is the difference between broad-spectrum and narrow-spectrum antibiotics? broad-spectrum – large groups narrow-spectrum – small range 4. Why is Mueller-Hinton agar used to test antibiotic susceptibility? contains starch (neutralizes toxins produced by the bacteria) 5. What is the difference between an antiseptic and a disinfectant? antiseptic – living tissue disinfectants – non-living

Section Eight: Microbial Genetics and Serology 1. What is hemagglutination? clumping together of red blood cells 2. What antigens are present on the surfaces of the erythrocytes in the following blood types? a. A+: A, Rh

b. AB-: AB c. O-: none d. O+: Rh e. B-: B 3. What do the following agglutination results signify? a. Anti-A: agg+, Anti-B: agg+, Anti-Rh: agg-: ABb. Anti-A: agg-, Anti-B: agg+, Anti-Rh: agg-: Bc. Anti-A: agg+, Anti-B: agg-, Anti-Rh: agg-: A+ 4. What are the consequences of giving a patient the wrong blood type in a transfusion? breathing difficulties, muscle ache, nausea, blood in urine, jaundice 5. What is the universal donor? The universal recipient? Why? donor – O-, no antigens on the surface of erythrocytes recipient – AB+, no antibodies 6. What does ELISA stand for? enzyme-linked immunosorbent assay 7. What are the differences between a direct and an indirect ELISA? direct – one antibody indirect – two antibodies 8. What are three settings in which one might use an ELISA? pregnancy test, HIV test, allergy test...