Streptococcus infections

Question 1

are streptococci a gram-positive or negative organism? What does it mean and what does it stain and in what colour?

Answer 1

Gram positive organism, stain will bind the peptidoglycan on outside of cell wall (no outer lipid membrane). Will stain purple.

Question 2

How does streptococcus characteristically grow?

Answer 2

in pairs or chains.

Question 3

What initial tests would you do for strept?

Answer 3

check growth on blood agar (horse blood +gelatin) in aerobic and anaerobic conditions.

Question 4

does strep gorw in aerobic or anaerobic conditions?

Answer 4

aerobically grows on blood agar.

Question 5

What three classes are gien based on haemolysis?

Answer 5

alpha haemolytic- will lyse blood and will produce H202 which makes green methlyglobin.

beta hamolytic- will completely lyse blood via steptolycin (O and S) O is oxygen sensitive, S isnt’.

gamma haemolytic- may look like strep with stains, but no haemolysis

Question 6

How can you further classify beta haemolytic strep?

Answer 6

Categoreised into lancefield groups based on carbodygrate antigen composition (A-G).

Question 7

How are alpha haemolytic streps separated and what are they?

Answer 7

Distuished with opticon (antibiotic) disc differs on their sensitivity.
S. pneumoniae or from s. viridans group (e.g. s. aures) which are your traditional commesnals.

Question 8

what are the A, B C and F strep belonging to the beta haemolytic group?

Answer 8

(A) s. pyogenes

b) s. agalactiae
c) s. dysgalactiae
f) s anginosus of milleri group.

Question 9

how can s. pneumoniae and s. pyogenes be subdivided?

Answer 9

s. pneumoiae subidved based on seroptypes (polysaccharaies capsules).
s. pyogenes subdivided based on M protein genetic sequences.

Question 10

What categories of virulence factors?

Answer 10

Those involved in:
colonisation,
invasion
evasion 
devastation

Question 11

What molecules help s.pneuominae colonise and bind to cells?

Answer 11

adhesins like Cbp-A binds to choline.

N-glycan degradation enzyme breaks down surface glycocalyx o allow cell access.

Question 12

What determines whether s. pneumoniae is virulent or commensal?

Answer 12

The cell numbers.

If viral infection present, number for virulence drastically reduced.

Question 13

How does s. pneuominae invade host?

Answer 13

traverse through the epithelium inside of vacuoles.

Rstrcition of colonies leads to lysis via autolysina nd penumolysin release.

Question 14

What feature of s. penumoniae is most important virulence factor for their evasion?

Answer 14

capsule- ones without capsule do not cause disease.

Question 15

Which s. pneumoniae proteins block complemnt?

Answer 15

pspA blocks C3 fixation.

pspC binds factor H to prevent C3b formation through the alternative pathway.

Question 16

which s. pneumoniae protein resists oxidative ROS?

Answer 16

psaA

Question 17

Which s. pneumoniae proteins break up IgA?

Answer 17

neuraminidases (removes secretory component), and also Ig1a protease (cleaves at hinge region)

Question 18

What toxins for devastation does s. pneumoniae use?

Answer 18

pneumolysin release upon colony restrction/ phagocytosis.
H202 production.
Superantigens: F-antigen and C-polysaccharide will induce inflammatory response for dissemination into the blood.

Question 19

What are the 9 diseases associated with s. pneumoniae infection?

Answer 19

otitis media (segun) , sinusitis (claudia), conjunctivitis, meningitis (sarahB) 
pneuomonia (Izzy B) empyema (anna), peritonitis (Han) osteomyleitis (Liz) speitci arthritis.

Question 20

What is otitis media, sinitis and conjunctivitis inflammation of? (s. pneumoniae)

Answer 20

inflammation of the middle ear (can lead to burst eardrum and pus discharge).
inflammation of nasal mucosa (potential to spread into brain)
inflammation of the conjunctiva lining the inside of the eylid- eye redness and inflammation.

Question 21

symptoms of meningitis (s. pneumoniae)

Answer 21

inflammation of meninges (surrounding CNS)
sensitivity to light, headache and neck stiffness.
Aggressive IV antibiotics requied/

Question 22

What occurs during pneumonia and what are symptoms? (s. pneumoniae but also other strep)

Answer 22

fluid and pus fills up the air sacs along with inflammation. Coughing with phleg,/ pus and fever and chills.

Question 23

Whats happens in empyema? (s. pneumoniae)

Answer 23

pus gathers in the pleural cavity.
fever chest pain and breathlessness.
severe cases require drainage and surgery (associated with 20% mortality)

Question 24

What occurs in peritonitis? (s. pneumoniae)

Answer 24

inflammation of peritoneum that surround the abdominal cavity- fever, abdominal pain/ nausea and accumulation of fluids in the peritoneal cavity and renal dysfunction.
Can sometimes use lavage to wash out bacteria.

Question 25

What are the molecules important for S. pyogenes adherence to epithelial and mucosal cells? (colonisiation)

Answer 25

M protein, lipoteich acid (LTA) (epithelial)

fibronectin binding protein (protein F) for mucosal cells.

Question 26

S. pyogenes invasion is much more aggressive than S. pneumoniae, what three enzzymes are important in invasion?

Answer 26

streptokinase
streptodonases
hyaluronidase
proteases

Question 27

What do streptokinases and streptodornases do in S. pyogenes infection?

Answer 27

lyses fibrin

The latter has Dnase and RNase activity

Question 28

What do hyaluronidase and proteases do in S. pyogenes infection?

Answer 28

digests host connective tissues (and S. pyogenes own capsule)
protests cause soft tissue necorsis.

Question 29

How does the M protein contribute to invasion and in S. pyogenes infection?

Answer 29

M proteins cause a local inflammatory reaction for the invasion of the blood stream.

Question 30

How does the M protein contribute to evasion and in S. pyogenes infection?

Answer 30

1) M protein can bind host antigens (to pretend that it is ‘self’) and induced tolerance and immunosuppression/
2) negative charge interferes with phagocytosis and complement deposition.

Question 31

How else is S pyogenes protected from drugs and the immune response, and from complement?

Answer 31

Forms a biofilm.
C5a peptidase will cleave C5
Spy|CEP cleaves human CXC chemokines.

Question 32

What toxins in S pyogenes cause lysis and fever and rash (in scarlett fever)

Answer 32

Stretptolysin (punches pores)
Streptodronases are leukotoxic.
proteases cause soft tissue damage.

Question 33

What happens in osteomyelitis?

Answer 33

inflammation of the bone tissue- bone destructi and necrosis.
Fever, loss of motion.
Prolonged antibiotics, surgery/amputation.

Question 34

Describe septic arthritis

Answer 34

When the infection is within the synovial fluid. Causes pain, erythea swelling and fever.
Joint aspiration to treat and antibiotic treatment.