1. Identification of unknown bacterium
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
Escherichia Salmonella
Klebsiella Shigella
Citrobacter Proteus

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 So it is Escherichia coli
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