Experiment 4 Identification of pathogenic bacteria

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Experiment 4Identification of pathogenic
bacteria

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Content

• Identification of Pathogenic Cocci from Clinical
  Specimen
• Coagulase Test
• Identification of Intestinal Pathogens from Feces
  
• Identification of bacteria in throat  

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Identification of Pathogenic Cocci from Clinical
Specimen
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Pathogenic Cocci
S. pneumoniae
staphylococcus
Streptococcus
N. gonorrhoeae
N.meningitidis
N.meningitidis
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Identification of Pathogenic Cocci from Clinical
Specimen
Pus Throat swab
smear?Gram stain?observe
37? 24h
Colonies observation
Blood agar
Biochemical reaction , Pathogenicity test
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• A presumptive diagnosis of meningococcal
  meningitis can be made if gram-negative cocci are
  seen in a smear of spinal fluid
• The finding of gram-negative diplococci within
  PMNs in a urethral discharge specimen is
  sufficient for diagnosis

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Identification of staphylococcus

• Staph. Aureus
  Staph. pidermidis
• Pigmentation Golden yellow
  White
• a-Hemolysin
  -
• Coagulase
  -
• Heat-stable nuclease test
  -
• Mannitol fementaion test
  -
• pathogenisis significant
  weak or none

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Identification of Streptococcus

• Clear zone beta-hemolytic streptococci
• No zone gamma-hemolytic streptococci
• Green zone alpha-hemolytic streptococci

• Small colonies?translucent?smoth?neat margin
• G ?arranged in strain

alpha-hemolytic streptococci
streptococcus pneumoniae
synanthrin - (violet)
(yellow) fermentation
test Bile-soluble test -(clouding)
(clear)
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Coagulase Test

• Coagulase
• Any bacterial component or
  product which causes coagulation in plasma
  containing an anticoagulant such as citrate,
  heparin or oxalate. Staphylocoagulase.
• free coagulase (detected in tube)
• Bound coagulase (detected in slide)
• pathogenic staphy. Aureus produces coagulase,
  while non-pathogenic strains are coagulase
  negative

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Coagulase Test
NS
NS
Staphy. Aureus
Staphy. Aureus
plasma
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Biochemical Reaction

• Carbohydrate fermentation
• methyl red test
• Voges-Proskauer test
• citrate utilization test
• Sulfide ( H2S ) production
• Indole production
• Urea hydrolysis

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fermentaton test
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methyl red test

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VP(Voges-Proskauer)test
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• H2S Production

Urease Test
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Indole Test Methyl Red (MR) Test
Voges-Proskauer (VP) Test Citrate Utilization
Test E.coli - - gas Bacillus -
-
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• Identification of Intestinal Pathogens from Feces

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  Selective medium----Salmonella-Shigella agar
plate (S-S plate)

• Pathogenic bacilli---lactose fermentaiong(-)
• small colonies, colorless,
• Nonpathogenic bacilli-- lactose fermentaiong ()
• large colonies, red,

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Differential medium ---- EMB(Eosin Methyl Blue)
Pathogenic bacilli-- lactose fermentaiong (-
) Small colonies, colorless Nonpathogenic
bacilli-- lactose fermentaiong( ) Violet-black
colonies
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Double sugar iron agar slant

• inoculatin
• observe
• upperlayer
• Lactose fermemtationpathogenic bacillired,
  nonpathogenic bacilli--yellow
• H2S
• underlayer
• Glucose fermemtation(acid, gas )
• motivation

lactose Fe2SO4 solid glucose Semi-solid Indicator
phenol red
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Specimen
Agglutinate with polyvalent antisera against
Salmonella Shigella
? Different with cocci
Streak on SS agar plate
37?
Serologic test
Biochemical reaction
24h
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Identification of enteric bacilli
lactose glucose
motivation H2S E.coli ??? ?
- Shigella
-?? - -
S.typhi -??
/-
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• ????
• ??2?/?,????????????1?/??,??1?/??
• ????1?/??

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Report-- Coagulase test (detected in slide)
Identification of bacteria in
throat principle procedure
result analysis
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