1-boy who kept falling ill

Question 1

what colour do gram negative stain? why?

Answer 1

pinky red because inner & outer membrane means dye not taken up

Question 2

what colour does gram positive stain? why?

Answer 2

purple because thick peptidoglycan layer

Question 3

what is a quick easy lab test to identify strep pneumoniae?

Answer 3

optichon disc = it’s an antibiotic used for screening (not people) and strep pneumoniae bacteria doesn’t go near it so if doesn’t go near then means sensitive to optichon so means it’s strep pneumoniae

Question 4

does strep pneumoniae live as colonisation?

Answer 4

yes, lives in mouth etc without causing infections

Question 5

what can happen if strep pneumonia gets in air and causes infection?

Answer 5

1. can grow and become normal flora in mouth
2. grow further in numbers and spread to cause inner ear infection or pneumonia in lungs = these can both get worse and grow into CNS causing meningitis etc

Question 6

what antibiotics should be given to treat sinusitis? (if needed)

Answer 6

1st = penicillin
2nd = clarithromycin

• for 5 days

Question 7

what antibiotics should be given for otitis media? (if needed)

Answer 7

1st = penicillin
2nd = clarithromycin

• for 5 days

Question 8

what is acute otitis media?

Answer 8

• ear infection caused by viruses & bacteria

Question 9

what are risk factors for otitis media?

Answer 9

smoking 2nd hand, no breast feed, going to nursery, craniofacial abnormalities

Question 10

are antibiotics usually needed for otitis media?

Answer 10

no, usually gets better by itself - antibiotics needed if systemically unwell or higher risk of complications or under 2 bilateral infections

Question 11

what is a serotype? (like a pneumococcal serotype?)

Answer 11

• serotype = same organism with different surface antigens
• strep pneumo has more than 100 different serotypes
• different serotypes behave differently and have different effects within the body

Question 12

what is the most important virulence factor for strep pneumoniae?

Answer 12

capsule - it means that the PAMPS (which are what WBCs usually bind to to make immune response) are covered by capsule so harder for body to fight infection

Question 13

how does body kill bacteria if has capsule?

Answer 13

MZ (marginal zone) B cells = B cells with IgM or IgG that are specific for polysaccharide antigens

Question 14

how can MZ B cells make strong response when binding with polysaccharide antigen even though no T cells? and why no T cells?

Answer 14

• no T cells because T cells only respond to protein antigens
• MZ B cells can still make strong response due to identical subunits of polysaccharide meaning multiple activations by identical polysaccharide antigens

Question 15

why (if there’s no vaccine) is there no memory B cell response with capsule bacterium?

Answer 15

because capsule bacteria cover protein antigens so only polysaccharide antigens are exposed which means only special MZ B cells can bind and no T cells (only bid to protein antigens) = you need T cells for memory response & plasma cells

Question 16

why is spleen important in immune mediated protections against encapsulated bacteria?

Answer 16

spleen is main supplier of MZ B cells & MZ macrophages
(found in marginal zone outside white pulp in spleen)

Question 17

when should you suspect immunodeficiency? i.e. what are the hints to immunodeficiency

Answer 17

• more than 4 new ear infections a year
• more than 2 sinus infections a year
• more than 2 months of antibiotics with little effect
• more than 2 pneumonias in a year
• failure to grow normally
• recurrent, deep skin or organ abscesses (very unusual in childhood)
• persistent thrush in mouth or fungal infection on skin
• need for IV antibiotics
• family history of immunodeficiency

Question 18

what does pneumococcal conjugate vaccines help do?

Answer 18

generates memory B cells from this vaccine