Identification techniques

Question 1

5 classes of proteobacteria

Answer 1

Alpha-proteobacteria
Beta-proteobacteria
Gamma-proteobacteria
Delta-proteobacteria
Epsilon-proteobacteria

Question 2

Enterobacteriales in what class?

Answer 2

Gamma-proteobacteria

Question 3

Escherichia, Salmonella, and Klebsella all belong to which family?

Answer 3

Enterobacteriaceae

Question 4

Examples of culture collections where strains are deposited

Answer 4

• American type culture collection
  -National Collection of Type cultures
  -Public Health England
  -NCIMB

Question 5

Is C. violaceum ATCC 12473 same as NCTC 9757? true or false

Answer 5

True

Question 6

Do bacterial strains within a single species behave differently?

Answer 6

Yes

Question 7

Classes 1-4

Answer 7

Class 1 - Non-pathogeneic e.g k12 E.coli
Class 2 - Potentially pathogenic e.g. K. pneumoniae
Class 3 - pathogenic e.g. legionella spp.
Class 4 - No known class 4 bacterium (most viruses)

Question 8

Howare classical taxonomy and identification completed?

Answer 8

• Relies on phenotypic analyses
• Morphology (cell size, shape, flagella), O2 tolerance
• G+C content of DNA
• Physiology and metabolism e.g. nutrient sources, Relationship to pH, temperature, salinity, products formed, Prescence of enzymes

Question 9

Cell morphology + Gram reaction

Answer 9

Differ in shape: Cocci or bacilli
Different in gram test - Gram-positive (Purplish blue) or Gram-negative (Pink)

Question 10

Cocci types

Answer 10

Coccus
Diplococci
Streptococci
Sarcina
Tetrad
Staphylococci
Diplococci encapculated

Question 11

Bacilli types

Answer 11

Coccobacillus
Bacillus
Palisades
Diplobacilli
Streptobacilli

Question 12

Oxygen tolerance types

Answer 12

Obligate aerobe - requires oxygen to survive
Obligate anaerobe - Requires no oxygen to survive
Facilitative anaerobe - Can live in aerobic or anaerobic consitions
Aerotolerant anaerobe - Can tolerate low concentrations of oxygen
Microaerophile - Requires low levels of oxygen to grow

Question 13

Endospores

Answer 13

• Survival forms produced under unfavorable conditions e.g. when nutrients run out
• Can survive 100s/1000s of years
• High resistance to heat, drying, radiation, chemicals
• Low water content
• Contain calcium diplocolinate
• Special proteins protect DNA

Question 14

Catalase test

Answer 14

h2o2 -> h2o + 1/2O2

Important in detoxifyibg h2o2 produced during metabolismP#

Positive result - Bubbles
Negative - No bubbles

Question 15

Oxidase activity

Answer 15

Detects the presence of cytochrome c and associated oxidase
Kovac’s reagent (N, N, N’, N’ - Tetramethyl-p-phenylenediamine dihydrochloride)
Colourless when reduced
Purple when oxidised

Question 16

Do you need more or less energy to break the GC bonds

Answer 16

More

Question 17

Growth on lactose test

Answer 17

Growth on lactose
- Production of acid (pH changes)
- pH indicator phenol red
- Red -> yellow
- production of gas

Question 18

Test for H2S

Answer 18

• Hydrogen sulphide production
• Formation of ferrous sulphide
• Fe2+ + S2- —> FeS (insoluble)
  Black - Positive result
  Orange - negative result

Question 19

What are API kits?

Answer 19

Media kits for isolate identification

Question 20

MacConkey’s agar for enterobactericae

Answer 20

Bile salts inhibit gram negative
+ve - Lac+ - acid - red - E.coli, E. aerogenes
Lac- - NH3 - colourless - P. vulgaris, S. aureus

Question 21

What grows on chocolate agar and how to distungish them

Answer 21

Haemophilus, Neisseria

Add antibiotic

Question 22

How do differentiate between Haemophilus and Neisseria

Answer 22

Make medium more selective through adding antibiotics which kill Haemophilus, but don’t kill Neisseria

Question 23

How to differentiate between coliforms and E. coli

Answer 23

Chromogenic
Coliforms - Pink
E. coli - Purple

Question 24

Listeria selective agar

Answer 24

Non-pathogenic Listeria colony - no halo
Pathogenic Listeria - Halo present

Question 25

Mannitol salt agar for coagulase positve Staphylococcus

Answer 25

Selects for GM +ve (high salt)
Mannitol fermentation - H+ - red to yellow
When using selective media ALWAYS include controls
positive control - Ferments mannitol produces H+
Negative control

Question 26

What percentage of bacterial strains can be lab cultured?

Answer 26

3%