Infectious disease

Question 1

What component of a cell wall makes an acid fast bacilli

Answer 1

Gram positive cell with mycolic acid which makes a waxy layer on the cell surface that needs acid in order to stain the cell

Question 2

Describe the cell wall layer of a gram negative bacilli

Answer 2

-inner cell membrane (phospholipid bilayer)
-periplasmic space
-thin peptidoglycan later

-outer phospholipid bilayer / cell membrane
-Lipopolysaccharid layer consisting of lipid molecule, polysaccharide then O antigen

Question 3

Describe Type 1, 2 and 3 exotoxins

Answer 3

Exotoxins are secreted by a bacteria- both gram positive and gram negative can do this

Type 1: create a super antigen bridge between an APC and T-cell creating a massive T-cell activation –> pro inflammatory cytokine storm

Type 2: damage host cell membrane
Type 3: cause intra-cellular damage

Question 4

Which bacteria secrete endotoxins
what are they
what do they do

Answer 4

Gram negative bacteria only
Lipopolysaccharides from the cell wall of gram negative bacteria released on cell death

Highly antigenic causing pro inflammatory cytokine release and surrounding cell tissue damage

Question 5

what are 4 gram positive rods

Answer 5

‘Long cocci dyed bright”
long cocci= rods
dyed bright = gram positve

Listeria
Clostridium species (difficule, tetani, botulism)
Diphtheria
Bacillus

Question 6

What bacteria are in group A, B, C and D Strep

What is the haemolytic group of each

Answer 6

Group A- strep pyogenes- B haemolytic
Group B- S agalactiae- B haemolytic
Group C- S equisimitis
Group D- Enterococcus - Y haemolytic

Question 7

A bacteria is catalase positive - what is the next test to identity it
-what could it be

Answer 7

coagulase

coagulase +ve: staph aureus
coagulase -ve: S. epidermis, s, saprophyticus

Question 8

A bacteria is catalase negative
What is the next test to identify it

What classes would this make

Answer 8

Haemolytic test

a-haemolytic: oxidise iron in RBC to make agar green. S.pneumonia and S. viridian’s

b-haemolytic: lysis of the RBC- S.pyogenes, S agalactiase

Y-haemolytic: no lysis- Enterococci

Question 9

What are two gram negative diplococci bacteria

Answer 9

N mengenitis
N gonorrhoea

Question 10

What type of bacteria is haemophillus influenza

Answer 10

Gram negative rod