Question

1. For each descriptor. Choose a potential group of bacteria. Choose a member of the group you selected, and devise a specific set of NON-GENETIC tests to identify the specific bacteria.
   1. Oxidase negative, motile, glucose fermenter, gram-negative, rod-shaped
      1. Group:
2. 2. Specific example:
3. 3. Lab tests:
4. 2. CAMP positive, tumbling, gram-positive, beta-hemolytic
      1. Group:
5. 2. Specific example:
6. 3. Lab tests:
7. 3. Coliform rod, Non-fermenter, sulfide producing, Gram, negative, Motile
      1. Group:
8. 2. Specific example:
9. 3. Lab tests:
10. 4. Gram-negative, facultative anaerobe, polar flagella, oxidase-positive, fermenter
       1. Group:
11. 2. Specific example:
12. 3. Lab tests:
13. 5. Helical, gram-negative, non-fermenter, coccoid in oxygen, polar flagellum
       1. Group:
14. 2. Specific example:
15. 3. Lab tests:

I believe he wants the group of bacteria that fall under the provided descriptor. I think the first one is Enterobacteriaceae...  

Answer 1

1.

• 1.

  Oxidase negative, motile, glucose fermenter, gram-negative, rod-shaped

  Group: Enterobacteriaceae

  Specific example: E.coli

  Lab tests:

  Tests	Result	Explanation of observation and result	Organism indicated
  Gram staining and shape	Gram negative rods	Gram negative organism stains with Safranin and appear red/pink. Gram positive bacteria stains with Crystal violet and appear purple/violet	May be Enterobacteriaceae
  Glucose fermentation	Acid/ gas positive	Thus, if glucose is fermented, acid produced causes change in pH. Observation is as turning of media from red to yellow. Gas is observed in Durham’s tube	May be E. coli
  MacConkey Agar	Lactose fermentation-pink/red	Differentiates lactose fermenters from non-fermenters	Indicates E. coli
  Eosin-methylene blue (EMB) agar:	Lactose fermentation-greenish	Selects for gram-negative bacteria. Differentiates lactose fermenters from no	E. coli produces greenish sheen on EMB

  2.

  CAMP positive, tumbling, gram-positive, beta-hemolytic

  Group: Bacillus (Listariaceae)

  Specific example: Listeria monocytogenes

  Lab tests:

  1. Hemolysis test

  Bacteria producing haemolysin, can cause partial or complete lysis of RBC. Different types of haemolysis are:

  · Alpha haemolysis: greenish- discoloration around the colony. Partial Haemolysis.

  · Beta Haemolysis: Complete haemolysis. Zone of clearing around colonies.

  · Gamma haemolysis: no haemolysis observed. Colonies may appear on media.

  CAMP test

  Streaking at right angles with central streak of Staphylococcus acting as beta hemolytic.

  Motility test- tumbling motility.

  3

  Coliform rod, Non-fermenter, sulfide producing, Gram, negative, Motile

  Group: Enterobacteriaceae

  Specific example: Salmonella typhi

  Lab tests:

  Tests	Result	Explanation of observation and result	Organism indicated
  Gram staining and shape	Gram negative rods	Gram negative organism stains with Safranin and appear red/pink. Gram positive bacteria stains with Crystal violet and appear purple/violet	May be Enterobacteriaceae
  Hydrogen sulfide H2S, production	H2S = Black coloration/ deposit	Positive	May be Salmonella
  To differentiate Salmonella and Shigella from other Enterobacteriaceae and to differentiate Salmonella from Shigella, the organisms are inoculated to Salmonella-Shigella agar.	Salmonella-Shigella agar is selective and differential medium.	It containsThiosulfate and ferric citrate to detect hydrogen sulfide production	Salmonella

  4.

  Gram-negative, facultative anaerobe, polar flagella, oxidase-positive, fermenter

  Group: Aeromonadaceae

  Specific example: Aeromonas hydrophila

  Lab tests:

  Tests	Result	Explanation of observation and result
  Catalase	Positive	Oxidative pathway indicated by bubble formation on addition of H2O2
  Oxidase	Positive	Oxidative pathway indicated
  Nitrate reduction	Can reduce nitrate, black	Facultative anaerobic

  5.

  Helical, gram-negative, non-fermenter, coccoid in oxygen, polar flagellum

  Group: Proteobacteria (Campylobacteriaceae)

  Specific example: Campylobacter jejuni

  Gram staining and shape	Gram negative spiral shaped
  Capsule staining	Capsulated
  Oxidase	Positive
  Nitrate	Positive