Short series of biochemical tests

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We identify intestinal bacteria (within the Enterobacteriaceae family) on the basis of the biochemical properties of individual genera. We use a short series of biochemical reactions for this. It is a series of test tubes in which various biochemical tests are performed. The summary of results is always characteristic of a certain genus. Tests include: fermentation of glucose, H2S formation, urease formation, Simmons citrate, and indole formation.

Glucose fermentation + gas formation[edit | edit source]

  • Glucose solution with bromothymol blue + gas
  • Principle: the reaction uses pH changes during fermentation of sugars + the gas is in the test tube upside down, if the bacteria produce gas, they accumulate in it and form a bubble.
  • Result:
    • Positive with bubble - yellow (glucose fermentation) + bubble
    • positive without bubble - yellow (glucose fermentation)
    • negative - green-blue (no fermentation).

H2S formation[edit | edit source]

  • Hajny medium (ferric ammonium citrate indicator)
  • Principle: lead sulfide elimination causes medium blackening.
  • Result:
    • positive - blackening
    • negative - red, yellow

Urease formation[edit | edit source]

  • Medium with urea
  • Principle: urease produced by bacteria breaks down urea in the medium, which leads to an increase in pH and the medium turns pink.
  • Result:
    • positive: medium color change
    • negative: green, yellow

Simmons citrate[edit | edit source]

  • medium with sodium citrate and bromothymol blue as an indicator
  • Principle: bacteria use sodium citrate as a carbon source, ammonia is released, this leads to the increase in the pH of the environment and bluing of the medium
  • Result:
    • positive: medium bluing
    • negative: green, yellow

Indole formation[edit | edit source]

  • Hottinger broth (contains tryptophan) + Ehrlich (paradimethylaminobenzaldehyde) or Kovács reagent
  • Principle: tryptophan is degraded by some bacteria, producing indole (indole-positive bacteria), the presence of which can be demonstrated by the addition of an agent.
  • Result:
    • positive: red ring on the surface
    • negative: yellow ring

Resolution of the most important bacteria [1][edit | edit source]

Distinguishing the most important bacteria
glucose lactose sucrose mannitol urea hydrogen sulfide indole
Escherichia Coli +g + +,- + - - +
Citrobacter freundii +g +,- -,+ + - + -
Klebsiella pneumoniae +g + + + + - -
Enterobacter aerogenes +g + + + - - -
Proteus mirabilis +g - r - + + -
Proteus vulgaris +g - + - + + +
Morganella morhanii +g,+ - - - + - +
Providentia rettregi +g,+ - r +,- + - +
Salmonella typhi + - - + - + -
other salmonellas +g - - + - + -
Shigella + - - +,- - - +,-
Serratia +g - + + r - -
Yersenia enterocolica + - + + + - -
  • fermentation with gas formation: +g
  • fermentation without gas formation: +
  • negative reactions: -
  • differing results: r

References[edit | edit source]

Related Articles[edit | edit source]

Citations[edit | edit source]

  1. ↑ {{#switch: book |book = Incomplete publication citation. COOPER, Marek, Andrej SOUČEK and Faith FRANKOVÁ, et al. Medical Microbiology : Bacteriology, virology, parasitology. Prague : Marvil, 1996. 558 s. pp. 262. 978-80-7262-438-6. |collection = Incomplete citation of contribution in proceedings. COOPER, Marek, Andrej SOUČEK and Faith FRANKOVÁ, et al. Medical Microbiology : Bacteriology, virology, parasitology. Prague : Marvil, 1996. 558 s. pp. 262. {{ #if: 8023802976 |978-80-7262-438-6} } |article = Incomplete article citation.  COOPER, Marek, Andrej SOUČEK and Faith FRANKOVÁ, et al. 1996, year 1996, pp. 262,  |web = Incomplete site citation. COOPER, Marek, Andrej SOUČEK and Faith FRANKOVÁ, et al. Marvil, ©1996.  |cd = Incomplete carrier citation. COOPER, Marek, Andrej SOUČEK and Faith FRANKOVÁ, et al. Marvil, ©1996.  |db = Incomplete database citation. Marvil, ©1996.  |corporate_literature = COOPER, Marek, Andrej SOUČEK and Faith FRANKOVÁ, et al. Medical Microbiology : Bacteriology, virology, parasitology. Prague : Marvil, 1996. 558 s. 978-80-7262-438-6} }, s. 262.

Literature[edit | edit source]

  • BEDNÁŘ, M, V FRAŇKOVÁ a J SCHINDLER, et al. Lékařská mikrobiologie – bakteriologie, virologie, parazitologie. 1. vydání. Praha : Marvil, 1996. 558 s. ISBN 80-238-0297-6.
  • ŠMÍROVÁ, Václava. Úvod do lékařské mikrobiologie. - edition. -. 
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