Bacteria

Question 1

Coagulase test

Answer 1

Mix bacteria with rabbit plasma
If strain produces coagulase see fibrin clot made (via coagulase activation of staphylothrombin to cleave fibrinogen)

+ve: staph aureus, staph epidermidis

Question 2

CLED plate

Answer 2

Deficient in electrolytes to stop proteus swarming
Has bromethyl blue indicator
- lactose fermenting go yellow

Question 3

MacConkey plate

Answer 3

Bile salts (for enteric bacteria)
PH indicator and lactose
- lactose +ve is red

Question 4

Lancefield grouping

Answer 4

Mix anti-sera with cell wall and look for agglutination

A) strep pyogenes
D) enterococcus faecalis

Question 5

Gram staining

Answer 5

Add crystal violet dye then iodine
Complex can be washed out from gram -ve by ethanol

Counter stain with safranin pink

Question 6

Oxidase test

Answer 6

Redox dye is turned I purple by cytochrome oxidase

Neisseria is oxidase +ve

Question 7

Albert stain

Answer 7

For corynebacterium diptheriae

To stain polyphospate granules

Question 8

Things that cause haemolysis

Answer 8

Strep pyogenes (complete)
Strep pneumoniae (partial) 
Viridans streptococcus (grey green partial)

Question 9

Catalase test

Answer 9

H202 converted to water and O2 so bubble seen

Staphylococci are catalase +ve
Enterococcus aren’t
Corynebacteria are +ve

Question 10

Nagler test

Answer 10

For alpha toxin of C perfringens

On side without antibodies, agar breaks down due to toxin

Question 11

Elek test

Answer 11

For DTX

Looking for immune precipitated via interaction of toxin with antibody

Question 12

Metronidazole sensitivity

Answer 12

Clostridia are sensitive (only anAerobes can reduce the parent drug)

Question 13

Pseudomonas aeuginosa

Answer 13

Obligate anaerobes so found in burns
Gram -ve rod
Oxidase +ve
Large green colonies

Question 14

Staph aureus

Answer 14

Gram +ve cocci
Yellow colonies
Coagulase and catalase +ve
May give haemolysis

Question 15

Staph epidermids

Answer 15

Gram +ve cocci
Catalase +ve
Coagulase -ve

Question 16

Streptococcus (all)

Answer 16

Gram +ve cocci
Incomplete or complete (pyogenes) haemolysis
Catalase -ve

Question 17

Corynebacteria diphtheria

Answer 17

Pale grey colones 
Gram +ve rod 
Catalase +ve 
Albert stain for poly phosphate granules 
ELEK test for toxin

Question 18

Neisseria pharynges

Answer 18

Gram -ve diplodocus

Oxidase positive

Question 19

Candida albicans

Answer 19

Yeast

Seem gram +ve

Question 20

Enterococcus faecalis

Answer 20

Gram +ve cocci
Catalase -ve
Lactose fermenting so red on macCinkey, yellow on CLED

Question 21

E. coli

Answer 21

Gram -ve rod

Red on macconkey

Question 22

Things causing haemolysis

Answer 22

Staph aureus sometimes
Streptococci (esp pyogenes)
Clostridium perfringens

Question 23

Salmonella

Answer 23

Gram -ve rod
White on macconkey
Group by seeotyoe
Large watery margins

Question 24

Bacteriodes fragilis

Answer 24

Rod gram -ve

Question 25

What is metronidazole sensitive

Answer 25

Bacteroides fragilis
Clostridium perfringens
All clostridium

Question 26

Clostridium perfringens

Answer 26

Gram +ve spore forming rod

Phospholiapse C positive