Bacteriology lab Flashcards Preview

MCD Y2: Laboratory diagnostic methods > Bacteriology lab > Flashcards

Flashcards in Bacteriology lab Deck (25):
1

Recall 2 examples of sterile-site bacteriology cultures

Blood
CSF

2

What is chocolate agar and what is it used for?

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

3

What is MacConkey agar used for?

Gram neg bacteria

4

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

Skin + soft tissue

5

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

Abdomen and urinary tract

6

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

Purple
Caught in thick peptidoglycan wall

7

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

Takes up pink counter-stain
Has additional outer membrane to prevent peptidoglycan interaction

8

Give an example of a gram neg bacterium

E coli

9

Give an example of a gram pos bacterium

Cocci

10

Describe the appearance of gram pos cocci on an agar plate

Forms clumps

11

Describe the appearance of gram pos staphyloccocci on an agar plate

Forms chains

12

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

Coagulase test

13

What is coagulase?

Staphylococcus virulence factor

14

Give an example of a coagulase positive virus

S. aureus

15

Name and describe the types of haemolysis

Alpha and beta
Alpha = incomplete
Beta = complete

16

What bacteria are frequently subjected to haemolysis testing?

Staphylococcus

17

How does alpha haemolysis appear?

Turns agar green

18

Give an example of a bacteria that undergoes alpha haemolysis

S. pneumoniae

19

How does beta haemolysis appear?

Clears agar

20

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

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

21

What sort of bacteria requires serology testing and why?

Syphillis - can't be cultured

22

How can serology be used to confirm a chickenpox diagnosis?

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

23

How is MRSA resistance tested for?

PCR for resistance gene (MecA)

24

Recall 2 ways of testing for antimicrobial susceptibility

MIC
Disc diffusion

25

Describe the relationship between MIC breakpoint and resistance

Concentration above breakpoint = resistant