Gram Positive Cocci

Question 1

What are examples of gram positive cocci?

Answer 1

Staphylococcus aureus
MRSA
Staphylococcus epidermidis
Streptococcus pneumoniae
Streptococcus pyogenes
Streptococcus mutans

Question 2

what are the pathological principles of Staphylococcus aureus?

Answer 2

colonises the skin + nostrils
transmitted by direct contact or fomites (objects likely to carry infection)

Question 3

Which infections does Staphylococcus aureus cause?

Answer 3

Endocarditis
Pneumonia
Osteomyelitis
Septic arthritis
Skin/soft tissue infections e.g. abscesses
Toxic shock syndrome (TSS)
Staphylococcal scalded-skin syndrome (Ritter disease)

Question 4

What are the risk factors of Staphylococcus aureus infection?

Answer 4

Immunosuppression
IV drug use
Recent invasive procedure
Foreign material in body
Dialysis

Question 5

What are secondary complications caused by Staphylococcus aureus infections?

Answer 5

Sepsis, bacteremia, invasive infection
Antibiotic resistance: resistance to penicillin G

Question 6

What are signs and symptoms of Staphylococcus aureus infection?

Answer 6

Skin soft tissue infections:
- erythema, swelling, warmth, Ritter’s disease

Systemic infections:
- joint pain, abdominal pain, headache, heart murmur

TSS:
- fever,rash, hypotension

Food borne illness:
- vomiting, diarrhoea

Question 7

How can you diagnose infections caused by Staphylococcus aureus?

Answer 7

Culture
PCR

Question 8

How is Staphylococcus aureus infection treated?

Answer 8

Medication’s:
- topical antibiotic (for skin infection)
Oral/ IV antibiotic:
- MRSA
- VRSA

Surgery;
Abscess drainage
Foreign material removal in body

Question 9

what are some virulence factors (factors which help cause disease) of Staphylococcus aureus?

Answer 9

cytolysins e.g. alpha-toxin or PVL, which destroy neutrophils
hemolysins which form pores in cells (e.g. macrophages, erythrocytes and lymphocytes)
superantigens e.g. enterotoxins, which stimulate activation of excessive amounts of T cells, which produces lots of cytokines causing uncontrolled inflammation

Question 10

what are the pathological principles of Staphylococcus epidermidis?

Answer 10

commonly associated with infection of surgical site, catheters and prosthetic devices
part of skin and normal flora

Question 11

Which infections does Staphylococcus epidermidis cause?

Answer 11

skin/mucous colonisation causes a barrier rupture which results in infection
forms biofilms on foreign materials in the body
can causes catheter-associated infections, prosthetic joint infections + endocarditis

Question 12

what are the risk factors of Staphylococcus epidermidis infections?

Answer 12

immunosuppression
neonates
recent invasive procedure
foreign material in body

Question 13

what are secondary complications caused by Staphylococcus epidermidis infections?

Answer 13

sepsis
bacteremia
in neonates: pneumonia, UTI, enterocolitis

Question 14

what are the signs and symptoms of Staphylococcus epidermidis infections?

Answer 14

local: pain, tenderness, swelling, warmth
systemic: fever, hypotension, leukocytosis

Question 15

how would you diagnose Staphylococcus epidermidis infections?

Answer 15

culture-based observations: blood, urine, synovial fluid
PCR amplification

Question 16

how is Staphylococcus epidermidis infection treated?

Answer 16

Medications:
oral antibiotics
empiric treatment (treatment given whilst waiting for results) is vancomycin

Surgery:
remove foreign material from body

Question 17

what are the basic pathological principles of Streptococcus pneumoniae?

Answer 17

causes several conditions in children and older adults
diplococci and forms chains

Question 18

what are the different virulence factors of Streptococcus pneumoniae?

Answer 18

• resistance to phagocytosis
• adherence proteins
• forms biofilm
• pneumolysin toxin
• asymptomatic colonisation so direct spread from site of colonisation, hematogenous spread which causes clinical syndrome

Question 19

which infections does Streptococcus pneumoniae cause?

Answer 19

meningitis
pneumonia
sinusitis

Question 20

what are the risk factors associated with Streptococcus pneumoniae infections?

Answer 20

age (<2, >65)
underlying diseases
crowded areas
immunodeficiency
smoking + alcohol abuse

Question 21

what are secondary complications caused by Streptococcus pneumoniae infections?

Answer 21

pneumococcal endocarditis
empyema
bacteremia
sepsis

Question 22

what are the signs and symptoms associated with Streptococcus pneumoniae infections?

Answer 22

common symptoms:
- fever, altered mental status, malaise

clinical syndrome symptoms:
- meningitis: headache, neck stiffness
- pneumonia: cough, bronchial breath sounds, rales
- sinusitis: purulent rhinitis, mucous membrane edema, headache

Question 23

how can you diagnose Streptococcus pneumoniae infections?

Answer 23

• chest x-rays
• PCR test
• urine antigen analysis (test for bacteremia)
• physical examination

Question 24

how can you treat infections caused by Streptococcus pneumoniae?

Answer 24

Medications:
- antibiotics
* pneumonia = beta-lactam antibiotics
* sinusitis = amoxicillin

Other interventions:
- pneumococcal vaccines

Question 25

what are the basic pathological principles of Streptococcus pyogenes?

Answer 25

AKA group A streptococcus (GAS)
beta-hemolytic
primarily infects skin + soft tissue

Question 26

what are the virulence factors of Streptococcus pyogenes?

Answer 26

vary with specific strains
- M proteins: protect microbe from humeral immune surveillance, resist phagocytosis
- Binding proteins: bind to IgG, IgM and IgA which are all important antibodies so it inhibits their proper function
- cytolysins e.g. streptolysins which bind to cholesterol on eukaryotic cell membranes causing cell lysis

Question 27

which infections are caused by Streptococcus pyogenes?

Answer 27

pyogenic diseases:
- pharyngitis + cellulitis
toxigenic diseases:
- scarlet fever, toxic shock syndrome
immunologic diseases:
- rheumatic fever

Question 28

what are some risk factors associated with infections caused by Streptococcus pyogenes?

Answer 28

susceptible host + encounter with streptococcus expressing virulence factors

Question 29

what are secondary complications caused by Streptococcus pyogenes?

Answer 29

tissue destruction
renal disease
sepsis
multiorgan failure
disseminated intravascular coagulation

Question 30

what are signs and symptoms associated with infections caused by Streptococcus pyogenes?

Answer 30

• pharyngitis: acute onset of sore throat, fever, pharyngeal edema
• cellulitis: erythema, edema, abscess formation
• impetigo: papules, vesicles,
• scarlet fever
• toxic shock syndrome

Question 31

how would you diagnose infections caused by Streptococcus pyogenes?

Answer 31

gram positive cocci
positive cultue
blood studies
clinical history

Question 32

how would you treat infections caused by Streptococcus pyogenes?

Answer 32

Medications:
- antibiotics

Surgery:
- surgical debridement