Medical Microbiology

Question 1

Gram Positive Cocci

Answer 1

Staphylococcus spp
Streptococcus spp

Question 2

GPC Grape-like clusters

Answer 2

Staphylococcus spp

Question 3

GPC Chains & clusters

Answer 3

Streptococcus spp.

Question 4

Staphylococcus culture conditions

Answer 4

Aerobic 37C Blood Agar

Question 5

Streptococcus culture conditions

Answer 5

Aerobic 37C/CO2 Blood Agar

Question 6

Staphylococcus spp colony morphology on agar

Answer 6

Blood Agar - 2-3mm round raised white/cream

Question 7

Blood Agar colonies
2-3mm, round, raised, white/cream

Answer 7

Staphylococcus spp.

Question 8

Staphylococcus spp Basic Characteristics

Answer 8

Gram Positive - grape-like clusters. Cocci.
KOH = Negative
Catalase = Positive
Oxidase = Negative

Question 9

Gram Positive = grape-like clusters
KOH = Negative
Catalase Positive
Oxidase Negative

Answer 9

Staphylococcus spp.

Question 10

Presumptive Staphylococci spp tests

Answer 10

1. Tube coagulase test
2. Stapharuex Plus test
3. DNase test
4. Mannitol Salt/CHROMID Agar

Question 11

Staphaurex Plus Test controls

Answer 11

Positive = Staph aureus
Negative = Staph epidermidis

Question 12

Preliminary Staph - DNase Test

Answer 12

1. Spot inoculum test + controls (pos=S.A, neg= S.E) with sterile loop on DNase agar plate.
2. Incubate at 37C for 24hrs
3. Incubated agar plates are flooded with 1M HCL solution for 10 mins.
   4, Plates are observed for a clear zone around colonies within 5 mins.

Positive result = Clear zone around colonies = S. Aureus
Neg = No clearing = S. epidermidis

Question 13

Staph. Aureus Selective/differential agar + Incubation

Answer 13

Mannitol Salt - incubate at 37C overnight
Positive = growth + fermentation (pink -> yellow) = Staph. Aureus
Negative = growth + no fermentation = S. epidermidis.

Question 14

Preliminary Staph test material

Answer 14

1. Tube coagulase - rabbit plasma
2. Staphaurex Plus - test kit
3. DNase test - DNA agar
4. Mannitol Salt - MS agar x2
5. CHROMID test- CHROMID agar x2
6. S.aureus control
7. S. epidermidis control.

Question 15

Gram Negative Coccobacilli on Chocolate agae

Answer 15

?Haemophilus spp

Question 16

GNCB (?Haemophilus) culture conditions

Answer 16

5-10% CO2 37C Chocolate agar

Question 17

Haemophillus spp. colony morphology on agar

Answer 17

Chocolate Agar
1-2mm, convex, grey-translucent, mucoid.

Question 18

Chocolate Agar - 5-10% CO2 37C
1-2mm, convex, grey-translucent, mucoid.

Answer 18

?Haemophilus spp.

Question 19

Gram Negative Coccobacilli Chocolate Agar
KOH Positive
Catalase Pos/Neg
Oxidase Positive

Answer 19

?Haemophilus

Question 20

Haemophilus Basic characteristics

Answer 20

Gram Negative coccobacilli
KOH positive
Catalase positive (H. Influenza)/ negative (H. Parainfluenza)
Oxidase Negative.

Question 21

Preliminary Haemophilus spp. tests

Answer 21

X and V Growth Factors
1. Prepare heavy inoculum (1-2 colonies in reduced water)
2. Lawn DST agar evenly
3. Allow suspension to dry
4. Use sterile forceps, place X, Y, XY disks in petri plate (3.5cm away)
5. Incubate at 5% CO2 overnight at 35-37C
6. Observe growth of bacteria in vicinity of disks.
Visible colonies around XV only = H. influenza
Visible colonies around XV + V = H. parainfluenza.

Question 22

Preliminary Haemophilus spp. test materials

Answer 22

X and V factor test
1. DST Agar x2
2. X,V,XV disks x2 each
3. Boujee with water x2
4. H. influenza control