Past Exam Qs

Question 1

Urease positive organisms

Answer 1

Proteus mirabilis
Helicobacter pylori
Pasteurella multicoda

Question 2

New York City agar

Answer 2

Used for Neisseria Gonorrhoeae
Enriched by lysed blood and yeast extract + antibiotics
Contains corn starch, peptone buffered with phosphates and supplemented with horse plasma, horse Hb, dextrose, yeast autolysate and antibiotics
Yeast fulfils the CO2 requirements needed to enhance CO2 growth

Question 3

DCA agar

Answer 3

Dexoycholate citrate agar
For non-lactose fermenting enterobacterales e.g, Salmonella and Shigella
Selective agents are sodium deoxycholate and sodium citrate
Differential agents are lactose and sodium ferric chloride
Shigella appears as a pale coloured colony
Lactose fermenters appear pink
Salmonella are pale with a dark centre (H2S positive)

Question 4

Baird Parker Media

Answer 4

Used for the selective isolation of staphylococci species
Contains lithium chloride and tellurite to inhibit the growth of alternative miccrobial flora
Included pyruvate and glycine promote the growth of staphylococci
Grow black in colour with clear zones around them

Question 5

Selenite broth

Answer 5

Used for selectice enrichment of Salmonella
Reduces growth of faecal coliforms
Broth is used by taking a sub-culture of broth from upper third of broth column at least 5cm in depth
Used for the better enrichement of Salmonella Typhi
Incubate at 37 degrees for no longer than 18 hours

Question 6

Modified CCDA

Answer 6

Charcoal cefoperazone deoxycholate agar
An improved version of CCD agar
Direct isolation of campylobacter from faeces
Charcoal, cefoperazone and sodium deoxycholate