L11 - Streptococci and EBV

Question 1

Streptococci and staphylococci are gram postivie cocci . However streptococci are catalase negative. Staphylococci form in clusters whereas streptococci exist as chains. Give an example of an alpha haemolytic, beta haemolytic and gamma haemolytic streptococci.
Explain each category

Answer 1

alpha - viridans streptococci (e.g. s. pneumoniae/s. mutans)
beta - streptococcus pyogenes
gamma - enterococcus faecialis

alpha - partial haemolysis (green in colour)
beta - complete haemolysis
gamma - no haemolysis

Above is talking about effects on RBC’s

Question 2

What is an alternate name for streptococcus pyogenes?

Answer 2

Group A beta-haemolytic strep (group A strep)

Question 3

Give two virulence factors of s. pyogenes

Answer 3

Capsule/M protein/streptolysins/streptokinase/adhesins

Question 4

List three diseases caused by S. pyogenes

Answer 4

Major cause of cellulitis/acute pharyngitis/impetigo/sepsis/toxic shock synfrome/erysipelas/necrotising fascitis

Question 5

What is the antiobiotic given for S. pyogenes infection?

Answer 5

flucoxacillin/ doxycycline if resistant

Question 6

Describe some symptoms of acute pharyngitis

Answer 6

abrupt sore throat/,alaise/fever/headache/lymphadenopathy/tonsil exudate/

Question 7

List two complications of streptococcal pharyngitis

Answer 7

scarlet fever (widespread rash due to haematogenous spread)/sepsis/arthritis/jaundice (its a b haemolysin)

due to production of pus - tonsillar abcesses/mastoiditis/sinusitis/meningitis/

rheumatic fever

glomerulanephritis

Question 8

Why are patients who get acute pharyngitis (tonsilitis) unlikely to get it again

Answer 8

Acquisition of an M protein antibody

Question 9

Explain the pathogenesis behind streptococcal toxic shock syndrome

Answer 9

deep tissue infection with s pyogenes -> bacteraemia -> vascular collapse -> organ failure

Question 10

Explain the purpose of the coagulase test and how its done

Answer 10

Coagulase testing is to differentiate coagulase positive staph aureus from coagulase negative staph. Add fibrinogen in plasma to the dish if catalase positive it will convert it to fibrin which is shown by it becoming clumpy.

Question 11

What are the two major causes of acute phayngitis?

Answer 11

S. pyogenes and EBV

Question 12

How would you distinguish bacterial pharnygitis (s. pyogenes) from viral pharyngitis (EBV)?

Answer 12

Viral will lack a cough, muscle aches, pus on tonsils and inflamed cervical glands. Mainly will just have a rapid onset of cough and some tonsil inflammation. In general to distinguish viral from bacterial, viral don’t have specific other symptoms, tend to be much more general unwellness.

Question 13

What kind of virus is the Epstein-Barr virus?

Answer 13

Herpes virus

Question 14

Infection with EBV in childhood is normally asymptomatic, but what disease does it often cause in adulthood?

Answer 14

Infectious mononucleosis (glandular fever)

Question 15

Explain the pathophysiology of glandular fever

Answer 15

Transmission of EBV via saliva -> colonisation of pharygneal epithelium and establishes a LATENT infection in B cells -> undyces the B cells to proliferate and thus cause a massive induction in their associated immunoglobulins -> inflammation.

Question 16

What is meant by a ‘latent’ virus?

Answer 16

REmains dormant but can be subsequently reactivated at a later date in times of immunocompromise

Question 17

What are the symtpoms and treatment for infectious mononucleosis?

Answer 17

Symptoms - fever, pharyngitis and lymphadenopathy of cervical nodes normally
AND splenomegaly often

Treatment - Rest, fluids and avoid contact sports because of splenomegaly

Question 18

What other diseases is EBV associated with except for infectious mononucleosis?

Answer 18

pharyngitis/Burkitt’s lympma/ risk factor for HIC, malaria and other malignancies

Question 19

What drug is the alternative to penicillins in kids with a penicillin allergy?

Answer 19

erythromycin