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PRACTICAL

PRACTICAL. Identification of unknown bacterium. Why species level identification required?. To know which species is involved in the particular condition To know the subspecies To further know the types Immunotypes, serotypes, chemotypes etc Epidemiological studies. Basic steps to follow.

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PRACTICAL

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  1. PRACTICAL Identification of unknown bacterium

  2. Why species level identification required? • To know which species is involved in the particular condition • To know the subspecies • To further know the types • Immunotypes, serotypes, chemotypes etc • Epidemiological studies

  3. Basic steps to follow

  4. Pure culture follow up-Day 1

  5. Pure culture follow up-Day 1

  6. First day – preliminary findings • Growth characteristics • Gram stain • Catalase • Oxidase • Motility

  7. Presumptive follow up

  8. Members of enterobacteriaceae:oxidase Negative Non enterobacteriaceae Oxidase positive • Escherichia • Klebsiella • Citrobacter • Salmonella • Shigella • Proteus • etc Vibrios Pseudomonas etc

  9. Members of enterobacteriaceae:oxidase Negative(example) • LF (ONPG) NLF • EscherichiaSalmonella • KlebsiellaShigella • CitrobacterProteus

  10. A gram negative rod on BA/Macconkey agars Non hemolytic, moist, irregular, flat, centrally raised, 3-5 mm colonies, Lactose fermenting, Flat,irregular centrally raised, moist 2-4 mm colonies

  11. Tests to read on second day • Check whether the culture is pure • Repeat catalase, oxidase,gram and motility to confirm previous day’s findings

  12. Biochemical tests TSI: A/A, Gas +, H2S Negative SIM: H2S,Neg, Indole: Positive., Motile Motility; (PW) Motile It could be ESCHERICHIA, CITROBACTER,OR ENTEROBACTER Glucose : Positive (Acid and Gas) Lactose : Positive Sucrose : Negative / Positive Mannitol : Positive Indole : Positive MR : Positive VP : Positive Citrate : Negative Urease : Negative Macconkey: LF Gram: Gram Negative rods Catalase: Positive Oxidase ; Negative LAO : +-+ Melonate: - KCN ; _ So it is Escherichia coli One of the members of Enterobacteriaceae

  13. For further details: Contact • Jasmn98

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