4 - streptococcus pyogenes

Question 1

morphology and capsule composition

Answer 1

-cocci in long chains
-hyaluronic acid (antiphagocytic)

Question 2

cultivation and hemolytic pattern

Answer 2

-1-2mm white pinpoint colonies
-wide b-hemolytic zone

Question 3

main virulence factors

Answer 3

-hyaluronic acid capsule

-adhesins: M-protein, fibrinogen/fibronectin binding proteins

-streptococcal pyrogenic exotoxin-erythrogenic exotoxin that causes scarlet fever, toxic shock syndrome

-streptolysin S: heat-labile hemolysin

-streptolysin O: heat-stable, lyses RBC/WBC/platelets detected via ASO test. helps with diagnosis

-streptokinase: cleaves plasminogen

Question 4

lytic enzyme virulence factors

Answer 4

-dezoxiribonucleae
-hyaluronidas: spread of bacterium
-C5a peptide: inhibits complement reaction

Question 5

role of CRP

Answer 5

c reactive protein
-acute phase protein that’s a marker of inflammation and activates complement system

Question 6

transmission

Answer 6

-by respiratory droplets/ close contact
-frequent nasal, pharyngeal carriage colonisation

Question 7

types of infections

Answer 7

-invasive, pyogenic infections
-toxin-mediated disease
-post streptococcal infections

Question 8

types of invasive, pyogenic infections

Answer 8

-head and neck
-skin and soft tissue

Question 9

head and neck infections (5)

Answer 9

invasive, pyogenic infection
*pharyngitis, tonsiliits - STREP throat
:sore throat, fever, nausea, swollen red pharynx, lymphadomegaly
*sinusitis
*otitis media
:pain, fever (bacteria enters euchastian tube)
*meningitis
*post partum sepsis

Question 10

skin and soft tissue infections

Answer 10

invasive, pyogenic infections
*erysipelas
:acute onset skin infection after micro trauma, red swollen painful area, sharp border and superficial, lymphangitis
*cellulitis
: inflammation of deeper layers of skin, diffuse infection of connective tissue, can lead to elephantiasis because of swelling/lymphatic drainage
*necrotizing facilitis
-deep infection of subcutaneous tissue, flesh eating bacteria

Question 11

2 types of post-streptococcal disease

Answer 11

-rheumatic fever
-poststreptococcal glomerulonephritis

Question 12

after what infections can each of the post streptococcal disease arise

Answer 12

-rheumatic fever can only occur after pharyngitis
-glomerular nephritis can occur after pharyngitis or skin infection

Question 12

rheumatic fever
what is it?
mechanism of molecular mimicry
symptoms of rheumatic fever
treatment

Answer 12

-a complication developing 2-4 weeks after a streptococcal infection
-based on molecular mimicry: M protein mimics our cells eg. myosin in our heart and cause our own antibodies to attack our own tissue eg. heart
J; polyarthritis, join pain
<3: pancarditis} heart murmur
N: subcutaneous nodules
E: erythema marginatum
S: chorea} CNS symptoms

-pencillin, salyicilic acid

Question 12

poststreptococcal glomerulonephritis
-what type of hyp sens reaction
-symptoms
-when
-mechanism

Answer 12

-type 3, not type 2
-dark urine, facial swelling: edema
-10 days after pharyngitis
-antigen-antibody complex deposit in glomerulus membrane

Question 13

diagnosis

Answer 13

-microscopy
-cultivation on blood agar
-bacitracin sensitive
-lanefield typing: latex agglutination

Question 14

treatment

Answer 14

-always sensitive to penicillin and other B-lactams
-penicillin allergy: macrolide