Tests for bacterial motility: Difference between revisions

Latest revision as of 21:13, 28 January 2022

Used to detect bacteria that are motile
Tube motility
- Stab an inoculum down into a tube with semisolid agar
- Check at intervals for diffuse, fuzzy growth that appears outside of the stab line
Wet prep
- Put a drop of inoculum in distilled water and check under a microscope
- Can compare to a drop of peptone water to identify Vibrio (motile in peptone water, not distilled)

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+* Used to detect bacteria that are motile
-Source: [https://microbeonline.com/tests-bacterial-motility-procedure-results/ microbeonline.com]
+* Tube motility
+** Stab an inoculum down into a tube with semisolid agar
+** Check at intervals for diffuse, fuzzy growth that appears outside of the stab line
+* Wet prep
+** Put a drop of inoculum in distilled water and check under a microscope
+** Can compare to a drop of peptone water to identify [[Vibrio]] (motile in peptone water, not distilled)
+[[Category:Diagnostics]]
-There are a variety of ways to determine motility of a bacterium—biochemical tests as well as microscopic analysis. If fresh culture of bacteria is available, microscopy is the most accurate way to determine bacterial motility and '''‘Hanging drop method’''' is a commonly used microscopic technique.
-Motile bacteria move about with structures called '''flagella''' (a few exceptional bacteria move with the help of axial filaments, which cannot be seen in the microscope). In semi-solid agar media, motile bacteria ‘swarm’ and give a diffuse spreading growth that is easily recognized by the naked eye.
-= Procedure =
-# Prepare a semisolid agar medium in a test tube.
-# Inoculate with a straight wire, making a single stab down the center of the tube to about half the depth of the medium.
-# Incubate under the conditions favoring motility.
-# Incubate at 37°C
-# Examine at intervals, e.g. after 6 h, and 1 and 2 days ''(depends on generation time of bacteria). Freshly prepared medium containing 1% glucose can be used for motility tests on anaerobes.''
-= Results =
-Hold the tube up to the light and look at the stab line to determine motility.
-# Non-motile bacteria generally give growths that are confined to the stab-line, have sharply defined margins and leave the surrounding medium clearly transparent.
-# Motile Bacteria: typically give diffuse, hazy growths that spread throughout the medium rendering it slightly opaque.
-[https://i0.wp.com/microbeonline.com/wp-content/uploads/2015/10/Test-for-Bacterial-Motility.png [[File:https://i2.wp.com/microbeonline.com/wp-content/uploads/2015/10/Test-for-Bacterial-Motility-300x210.png?resize=300%2C210|Test for Bacterial Motility: Center (Non-motile); Corners (Motile)]]]
-Test for Bacterial Motility: Center (Non-motile); Corners (Motile)
-= Laboratory Use =
-In laboratory Motility testing using semi-solid medium is commonly used for the identification of gram negative bacteria of '''Enterobacteriaceae family.''' Motility testing is done in conjunction with other biochemical testing using special bio-chemical media.
-# Sulfide Indole Motility '''(SIM)''' Medium: It is a semisolid agar used to determine hydrogen sulfide (H2S) production, '''indole formation,''' and '''motility.'''
-# Motility Indole urease '''(MIU)''' test: It is used to determine Motility, indole formation and '''Urease Test.'''
-Motility test is also used for the species differentiation of gram positive cocci, Enterococci. ''Enterococcus faecium'' and ''E. faecalis'' are non-motile, whereas ''E. gallinarum and E. casseliflavus/E. flavescens'' generally are motile.
-'''Note:''' Incorporation of tetrazolium chloride at a final concentration of 0.005% in the medium is helpful. The tetrazolium makes the motility agar much '''easier to read''' for motility. Tetrazolium is colourless in oxidized form, but the '''reduced salt is red''' (occurring as a result of bacterial metabolism) and indicates where bacterial growth has occurred.
-= Specific tests for bacterial motility determination =
-== Distilled water motility test ==
-It is a simple and very useful test to differentiate ''Vibrio species'' (gram negative motile curve rod) and ''Aeromonas species'' (gram negative motile rod). Aeromonas species will grow on [https://microbeonline.com/macconkey-agar-mac-composition-preparation-uses-and-colony-characteristics/ '''MacConkey agar'''] and sometimes on [https://microbeonline.com/thiosulfate-citrate-bile-salts-sucrose-tcbs-agarcomposition-uses-colony-characteristics/ '''TCBS'''], producing yellow colonies. Both of them are [https://microbeonline.com/oxidase-test-principle-procedure-and-oxidase-positive-organisms/ '''oxidase''' ]positive.
-'''Procedure:'''
-# Mix a loopful of growth from a nutrient agar subculture in a drop of sterile distilled water on one end of a slide. On the other end of the slide, mix another loopful of growth in a drop of peptone water.
-# Cover each preparation with a cover glass.
-# Examine microscopically using the 40 objective.
-'''Results:''' '''All Vibrio species are immobilized in distilled water but remain motile in peptone water'''. ''Aeromonas'' species remain motile in distilled water and peptone water.
-[[Category:Methods in microbiology]]