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Enzyme Tests

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Topic updated on 03/14/15 5:05pm

Overview
  • The presence or absence of specific enzymes can be used to distinguish bacteria in the laboratory
    • urease
    • catalase
    • coagulase
    • oxidase
Urease
  • Catalyzes the hydrolysis of urea into carbon dioxide and ammonia
  • Increase in urine pH leads to renal calculi
  • Urease positive bugs ("Urease Contaminates Kidneys. Now Peeing Hurts.")
    • Proteus spp.
    • Helicobacter pylori
    • Klebsiella pneumoniae
    • Ureaplasma urealyticum
    • Nocardia spp.
    • Cryptococcus neoformans
Catalase
  • Decomposes hydrogen peroxide before the host can use it to fight infection
    • H2O2 normally converted to microbicidal products by the enzyme myeloperoxidase
    • particularly a problem in people with chronic granulomatous disease (NADPH oxidase deficiency)
      • diseased host does not make enough H2O2
  • Catalase positive
    • Staphylococci (all species)
      • "they have enough 'staff' to make catalase"
    • Nocardia spp.
    • Serratia marcescens
    • Aspergillus spp.
  • Catalase negative
    • Streptococci (all species)
    • most anaerobes
Coagulase
  • Coagulase positive
    • Staphylococcus aureus
    • Yersinia pestis
Oxidase
  • Oxidase positive
    • Neisseria spp.
    • most Gram-negative bacteria
  • Oxidase negative
    • Enterobacteriaceae


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