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8/9/2019 Characterisation of Bacteria
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Based on phenotype
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Study of diversity of microorganisms andtheir relationships
Includes:clasi cation (ordering of B. into groups)nomenclatureidenti cation
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Morfological (cels including staining) Cultural Physiological
utritional Biochemical !cological "enetic #ntigenic Phage suscepti$ility
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#s many charactes as posi$le should $estudied
descri$tion of ne% species
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um$er of tests applied should $e &ept toa minimum
concetration for simple methods and for
characters %ith very good distinguishing value
tests must $e standardi'ed
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0.1est for o*ygen re2uirements 3.1est for dissimilation of glucose
(o*idative4fermentative) 5.Select tests useful for distinguishing
$et%een the genera 6.Select the test apllica$le for species
identi cation
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7etermination of shape "ram reaction Motlity
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8*idase test Catalase test Car$ohydrate $rea&do%n 8+9 of glucose #cid formation from sugars "as formation from glucose 8 P" test ($eta+galactosidase activity)
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eduction of nitrate to nitrite Indole test ;P test (acetoin production) #rginin dihydrolase test
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( Sulphide Indole Motility medium) +com$ination di
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1he IMViC tests are a group of individualtests used in micro$iology la$ testing toidentify an organism in the coliform group
# coliform is a gram+ = aero$ic orfacultative anaero$ic rod %hich producesgas from lactose %ithin /6 hours.
1he presence of some coliforms indicatefecal contamination.
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Species Indole Methyl ed ;oges+Pros&auer Citrate
Escherichia coli
Positive Positive egative egativeShigella spp. ? @ egative Positive egative egative
Salmonella s pp. egative Positive egative Positive
Klebsiella sp p. egative egative Positive Positive
Proteusvulgaris ?,@ Positive Positive egative egative
Proteusmirabilis egative Positive egative Positive
Enterobacter aerogenes egative egative Positive Positive
these IMViC tests are useful for differentiating thefamily Enterobacteriaceae, especially when used alongsidethe Urease test.
The IMViC results of some important species are shownbelow.
http://en.wikipedia.org/wiki/Escherichia_colihttp://en.wikipedia.org/wiki/Shigellahttp://en.wikipedia.org/wiki/Shigellahttp://en.wikipedia.org/wiki/IMViChttp://en.wikipedia.org/wiki/IMViChttp://en.wikipedia.org/wiki/Shigellahttp://en.wikipedia.org/wiki/Escherichia_colihttp://en.wikipedia.org/wiki/Escherichia_coli
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contains general nutrients and 5% sheep blood It is useful for cultivating fastidious organisms 4determining the hemolytic
capa$ilities of an organism. Some $acteria produce e*oen'ymes that lyse red $lood cells and degrade
hemoglo$inA these are called hemolysins. Bacteria produce di
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This streptococcus pyogenesexhibits β-hemolysis.
Examples of the blood culture patterns created by (from left)alpha-, beta- and gamma-
hemolytic streptococci.
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"iven a mi*ed $roth culture containingStaphylococcus aureus, Bacillus subtilis,Salmonella typhi and Shigella
dysenteriae, descri$e a systematicapproach to separate and con rm theidentity of each of these $acteria .
( 5 mar!s"
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1%enty students %ere hospitali'ed afterta&ing $rea&fast from a school canteen. #sample of drin& from the canteen %as sentto a micro$iologist to determine the causeof the pro$lem. 1he only informationavaila$le is that the sample contains grampositive cocci $acteria. #s a micro$iologistdescri$e a systematic approach todetermine the concentration of $acteria inthe sample and the identity of the $acteria.
( 0 mar&s)
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1here are three (,) di