IDENTIFIKASI BAKTERI

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IDENTIFIKASI BAKTERI

• OLEH
• SUDRAJAT
• FMIPA UNMUL
• 2009

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A. KARAKTERISTIK FENOTIF

• Metabolic differences
• Colony morphology
• Colonies can exhibit macroscopic differences
• e.g., Colonies of streptococci generally form
  fairly small colonies
• e.g., Colonies of Serratia marcescens produce a
  pigment and are often red when incubated at 22oC
• e.g., Colonies of Pseudomonas aeruginosa often
  produce a soluble greenish pigment

Pseudomonas aeruginosa
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A. KARAKTERISTIK FENOTIF

• Metabolic differences
• Culture characteristics
• Selective and differential media can aid in the
  identification of microbes
• Selective media favors the growth of certain
  types of microbes by inhibiting the growth of
  others
• Differential media contains a substance that
  certain bacteria change in a recognizable way

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A. KARAKTERISTIK FENOTIF

• Metabolic differences
• Culture characteristics
• MacConkey agar is both selective and
  differential
• Bile salts and dyes inhibit all but certain
  gram-negative rods
• Selective
• Acid produced by bacteria able to ferment lactose
  will turn a pH indicator red and form red
  colonies
• Differential

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A. KARAKTERISTIK FENOTIF

• Metabolic differences
• Culture characteristics
• Blood agar can be used to detect bacteria
  producing hemolysins
• e.g., Harmless Streptococcus species residing in
  the throat often cause alpha-hemolysis
• Greenish clearing around colonies
• e.g., Strep throat-causing Streptococcus
  pyogenes causes beta-hemolysis
• Clear zone around colonies

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A. KARAKTERISTIK FENOTIF

• Metabolic differences
• Culture characteristics
• Media lacking nitrogen can be used to detect
  nitrogen-fixing bacteria
• e.g., Azotobacter can be identified from soil
  samples incubated aerobically on such media

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A. KARAKTERISTIK FENOTIF

• Metabolic differences
• Biochemical tests
• Generally necessary for more conclusive
  identification
• Most rely on pH indicator or color change when a
  compound is degraded

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A. KARAKTERISTIK FENOTIF

• Metabolic differences
• Biochemical tests
• Sugar fermentation
• e.g., Lactose, sucrose, glucose, etc.
• Fermentation results in acid production
• pH indicator changes color
• Pink ? yellow
• Inverted tube (Durham tube) collects any gas
  produced

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A. KARAKTERISTIK FENOTIF

• Metabolic differences
• Biochemical tests
• Urease detection
• Enzyme degrading urea
• Urea ? CO2 NH3
• pH indicator turns bright pink in alkaline
  conditions
• Helicobacter pylori can be detected using a
  breath test

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A. KARAKTERISTIK FENOTIF

• Metabolic differences
• Biochemical tests
• Urease detection
• Helicobacter pylori can be detected using a
  breath test
• Causative agent of most stomach ulcers
• Culturing not necessary
• Patient drinks solution containing 14C-labeled
  urea
• 14C in expired are indicates presence of urease

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A. KARAKTERISTIK FENOTIF

• Metabolic differences
• Biochemical tests
• Catalase
• Commonly occurring enzyme
• Possessed by most bacteria growing in the
  presence of oxygen
• Absent in lactic acid bacteria
• e.g., Streptococcus
• Beta-hemolytic catalase-negative bacteria from a
  throat culture may be Streptococcus pyogenes

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A. KARAKTERISTIK FENOTIF

• Metabolic differences
• Biochemical tests
• Catalase
• Simple assay
• H2O2 ? H2O O2
• O2 bubbles are visible

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A. KARAKTERISTIK FENOTIF
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A. KARAKTERISTIK FENOTIF

• Organisms are identified using a dichotomous key
• Multiple biochemical and other tests are
  typically required
• Multiple tests are generally run concurrently
• Avoids waiting for incubation time for each test

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A. KARAKTERISTIK FENOTIF

• Metabolic differences
• Biochemical tests
• Commercial modifications of traditional
  biochemical tests
• e.g., APITM system, EnterotubeTM

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Metabolic Phenotypic Exam

• cultural approaches
• required for positive diagnosis of infection
• isolation and ID of pathogen
• accuracy, reliability, and speed
• specimen collection is important
• commonly used for positive identification of most
  prokaryotes
• methods used include
• culture characteristics
• biochemical reactions process

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Metabolic Phenotypic Exam

• culture characteristics
• organisms grown in a pure culture are easier to
  identify due to the high number of organisms
  obtained

E. coli
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Metabolic Phenotypic Exam

• culture characteristics
• use of selective or differential media can
  provide additional information
• selective media inhibits the growth of organisms
  other than the one being sought
• differential media contains substances that
  particular bacteria change in a recognizable way

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Metabolic Phenotypic Exam
When identifying a suspected organism, a series
of differential media is inoculated. After
incubation, each medium is observed to see if
specific end products of metabolism are present.
This can be done by adding indicators to the
medium that react specifically with the end
product being tested, giving some form of visible
reaction such as a color change. The results of
these tests on the suspected microorganism are
then compared to known results for that organism
to confirm its identification.
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Metabolic Phenotypic Exam
Some bacteria will produce the enzyme catalase.
Catalase will break down hydrogen peroxide
releasing oxygen, which is indicated by the
bubbles that have formed.