Lab Quiz 3 Notes PDF

Lab Quiz 3 Notes 5-15, 5-22, 4-4, 5-20 (Optochin) 5-15 Urease - Urease: enzyme that hydrolyzes urea into ammonia and carbon dioxide - Ammonia can be nitrogen source, enzyme activity can counteract acidity - Positive results in most enteric bacteria - Genes activated in...

Lab Quiz 3 Notes 5-15, 5-22, 4-4, 5-20 (Optochin) 5-15 Urease - Urease: enzyme that hydrolyzes urea into ammonia and carbon dioxide - Ammonia can be nitrogen source, enzyme activity can counteract acidity - Positive results in most enteric bacteria - Genes activated in presence of urea or absence of sufficient source - Pink broth within 24 hours is positive, slower positive after 24 hours - Contents - Trace of yeast extract for nutrients - Buffer to prevent alkalinization of medium - Phenol red (yellow below pH=8.4, pink above pH=8.4) - Differentiates Proteus (and Morganella morganii, Providencia) for being rapid positive, H, pylori, S. salivarius 5-22 CAMP - CAMP factor: hemolytic protein that interacts with S. aureus β-hemolysin - Streak on blood agar creates arrowhead zone of hemolysis if positive - S. agalactiae returns positive result, differentiates from other strep 4-4 MacConkey - MacConkey agar: undefined selective and differential test, contains lactose, bile salts, neutral red, and crystal violet, pancreatic digests - Crystal violet and bile salts inhibit g+ growth - Red dye is colorless above pH=6.8, red less - Fermentation of lactose creates acid end-products - Results - Growth: g-; no growth: g+ - Pink color: lactose fermenter; colorless: non-lactose fermenter - Differentiates Enterobacteriaceae 5-20 Optochin - Optochin- quinine that inhibits ATP synthase - Susceptibility is zone of clearing of 14mm - Differential for S. pneumoniae from other α-hemolytic strep - 5μg on a 6mm diameter disk