Microbiology- bacteria

Question 1

What colour do gram negative bacteria appear under the microscope?

Answer 1

pink

Question 2

What colour do gram positive bacteria appear under the microscope?

Answer 2

purple

Question 3

Describe blood agar

Answer 3

contains sheeps/horse blood

Question 4

Describe chocolate agar

Answer 4

Contains blood agar heated to 80 degrees c for 5 minutes. This releases some of the nutrients into the agar to make it easier to grow certain organisms that do not grow easily.

Question 5

What does CLED agar stand for?

Answer 5

cysteine lactose electrolyte deficient

Question 6

What colour is a lactose fermenting gram negative bacilli on CLED agar?

Answer 6

yellow

Question 7

What colour is non-lactose fermenting gram negative bacilli on CLED agar?

Answer 7

blue

Question 8

What type of bacteria is MacConkey agar primarily designed to grow?

Answer 8

gram negative bacilli

Question 9

What does MacConkey agar contain that inhibits gram positive bacteria?

Answer 9

bile salts

Question 10

Does MacConkey agar contain lactose?

Answer 10

yes

Question 11

What colour are lactose fermenters on MacConkey agar?

Answer 11

pink

Question 12

What colour are non-lactose fermenters on MacConkey agar?

Answer 12

yellow/colourless

Question 13

What type of agar would you use to grow Neisseria spp. ?

Answer 13

gonococcus agar

Question 14

What type of agar would you use to isolate salmonella spp. or shigella spp. ?

Answer 14

XLD agar

Question 15

How do colonies of salmonella and shigella look on XLD agar?

Answer 15

salmonella- red with black centres

shigella- red

Question 16

What type of agar is used to culture fungi?

Answer 16

Sabouraud’s agar

Question 17

Which genus of bacteria is gram positive cocci and arranged in clusters?

Answer 17

Staphylococcus

Question 18

What genus of gram positive cocci is found in chains?

Answer 18

Streptococcus

Question 19

For what genus of gram positive cocci would you carry out haemolysis on blood agar to classify further?

Answer 19

Streptococcus

Question 20

Describe the arrangement of Staphylococcus

Answer 20

clusters

Question 21

Describe the arrangement of Streptococcus

Answer 21

chains

Question 22

How are beta haemolytic strep further classified?

Answer 22

by antigenic group

Question 23

Are viridan’s strep alpha or beta haemolytic?

Answer 23

alpha

Question 24

What type of alpha haemolytic strep is sensitive to the optochin test?

Answer 24

S. pneumoniae

Question 25

Which Staphylococcal species will produce a positive coagulase test?

Answer 25

S. aureus

Question 26

Describe the disease causing potential of Staphylococcus aureus compared to Staphylococcus epidermidis ?

Answer 26

Disease causing potential of S. aureus is high | Disease causing potential of S. epidermidis is low

Question 27

What colour are S. aureus colonies on blood agar ?

Answer 27

gold (aureus is latin for gold)

Question 28

Which out of S. aureus and S. epidermidis displays coagulase activity?

Answer 28

S. aureus

Question 29

Describe the colonies of S. epidermidis

Answer 29

White/not pigemented

Question 30

coagulase-negative staphylococci are a common cause of what infection?

Answer 30

line infection

Question 31

What does a positive coagulase test look like?

Answer 31

clot formation in test tube

Question 32

Describe what beta haemolysis looks like on blood agar

Answer 32

clearing of agar round colonies

Question 33

describe what alpha haemolysis looks like on blood agar?

Answer 33

greening of agar round colonies

Question 34

How do you test alpha haemolytic strep for S.pneumoniae?

Answer 34

optochin test

Question 35

What can Streptococcus pneumoniae cause?

Answer 35

lobar pneumoniae and meningitis

Question 36

What further grouping can we do to beta haemolytic streptococci?

Answer 36

Lancefield grouping

Question 37

What antigen do enterococci have?

Answer 37

D

Question 38

What antigens on beta haemolytic streptococci can cause skin infection and tonsilitis?

Answer 38

A, C and G

Question 39

What can beta haemolytic strep with B antigen cause?

Answer 39

neonatal sepsis and meningitis

Question 40

What type of haemolysis is it when there is a clear zone around colonies?

Answer 40

beta