Bacteriology lab

Question 1

Recall 2 examples of sterile-site bacteriology cultures

Answer 1

Blood

CSF

Question 2

What is chocolate agar and what is it used for?

Answer 2

Cooked blood
Cooking released certain nutrients to allow for bacterial growth
Used for: H. influenzae

Question 3

What is MacConkey agar used for?

Answer 3

Gram neg bacteria

Question 4

In general what sort of infections are caused by gram pos bacteria?

Answer 4

Skin + soft tissue

Question 5

In general what sort of infections are caused by gram neg bacteria?

Answer 5

Abdomen and urinary tract

Question 6

What colour does gram stain turn in gram pos bacteria and why?

Answer 6

Purple

Caught in thick peptidoglycan wall

Question 7

What colour does gram stain turn in gram neg bacteria and why?

Answer 7

Takes up pink counter-stain

Has additional outer membrane to prevent peptidoglycan interaction

Question 8

Give an example of a gram neg bacterium

Answer 8

E coli

Question 9

Give an example of a gram pos bacterium

Answer 9

Cocci

Question 10

Describe the appearance of gram pos cocci on an agar plate

Answer 10

Forms clumps

Question 11

Describe the appearance of gram pos staphyloccocci on an agar plate

Answer 11

Forms chains

Question 12

What test is used to distinguish what form of staphylococcus is causing an infection?

Answer 12

Coagulase test

Question 13

What is coagulase?

Answer 13

Staphylococcus virulence factor

Question 14

Give an example of a coagulase positive virus

Answer 14

S. aureus

Question 15

Name and describe the types of haemolysis

Answer 15

Alpha and beta
Alpha = incomplete
Beta = complete

Question 16

What bacteria are frequently subjected to haemolysis testing?

Answer 16

Staphylococcus

Question 17

How does alpha haemolysis appear?

Answer 17

Turns agar green

Question 18

Give an example of a bacteria that undergoes alpha haemolysis

Answer 18

S. pneumoniae

Question 19

How does beta haemolysis appear?

Answer 19

Clears agar

Question 20

What agar is used to test for salmonella, and how does a positive test show?

Answer 20

XLD agar
(xylose lysine deoxycholate)
Salmonella can’t ferment xylose
Pos = goes pink, forms black colonies

Question 21

What sort of bacteria requires serology testing and why?

Answer 21

Syphillis - can’t be cultured

Question 22

How can serology be used to confirm a chickenpox diagnosis?

Answer 22

Culture taken at beginning of infection and after 10 days should go from IgG neg to pos

Question 23

How is MRSA resistance tested for?

Answer 23

PCR for resistance gene (MecA)

Question 24

Recall 2 ways of testing for antimicrobial susceptibility

Answer 24

MIC

Disc diffusion

Question 25

Describe the relationship between MIC breakpoint and resistance

Answer 25

Concentration above breakpoint = resistant