Gram Positive Cocci Flashcards
What are examples of gram positive cocci?
Staphylococcus aureus
MRSA
Staphylococcus epidermidis
Streptococcus pneumoniae
Streptococcus pyogenes
Streptococcus mutans
what are the pathological principles of Staphylococcus aureus?
colonises the skin + nostrils
transmitted by direct contact or fomites (objects likely to carry infection)
Which infections does Staphylococcus aureus cause?
Endocarditis
Pneumonia
Osteomyelitis
Septic arthritis
Skin/soft tissue infections e.g. abscesses
Toxic shock syndrome (TSS)
Staphylococcal scalded-skin syndrome (Ritter disease)
What are the risk factors of Staphylococcus aureus infection?
Immunosuppression
IV drug use
Recent invasive procedure
Foreign material in body
Dialysis
What are secondary complications caused by Staphylococcus aureus infections?
Sepsis, bacteremia, invasive infection
Antibiotic resistance: resistance to penicillin G
What are signs and symptoms of Staphylococcus aureus infection?
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
How can you diagnose infections caused by Staphylococcus aureus?
Culture
PCR
How is Staphylococcus aureus infection treated?
Medication’s:
- topical antibiotic (for skin infection)
Oral/ IV antibiotic:
- MRSA
- VRSA
Surgery;
Abscess drainage
Foreign material removal in body
what are some virulence factors (factors which help cause disease) of Staphylococcus aureus?
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
what are the pathological principles of Staphylococcus epidermidis?
commonly associated with infection of surgical site, catheters and prosthetic devices
part of skin and normal flora
Which infections does Staphylococcus epidermidis cause?
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
what are the risk factors of Staphylococcus epidermidis infections?
immunosuppression
neonates
recent invasive procedure
foreign material in body
what are secondary complications caused by Staphylococcus epidermidis infections?
sepsis
bacteremia
in neonates: pneumonia, UTI, enterocolitis
what are the signs and symptoms of Staphylococcus epidermidis infections?
local: pain, tenderness, swelling, warmth
systemic: fever, hypotension, leukocytosis
how would you diagnose Staphylococcus epidermidis infections?
culture-based observations: blood, urine, synovial fluid
PCR amplification
how is Staphylococcus epidermidis infection treated?
Medications:
oral antibiotics
empiric treatment (treatment given whilst waiting for results) is vancomycin
Surgery:
remove foreign material from body
what are the basic pathological principles of Streptococcus pneumoniae?
causes several conditions in children and older adults
diplococci and forms chains
what are the different virulence factors of Streptococcus pneumoniae?
- resistance to phagocytosis
- adherence proteins
- forms biofilm
- pneumolysin toxin
- asymptomatic colonisation so direct spread from site of colonisation, hematogenous spread which causes clinical syndrome
which infections does Streptococcus pneumoniae cause?
meningitis
pneumonia
sinusitis
what are the risk factors associated with Streptococcus pneumoniae infections?
age (<2, >65)
underlying diseases
crowded areas
immunodeficiency
smoking + alcohol abuse
what are secondary complications caused by Streptococcus pneumoniae infections?
pneumococcal endocarditis
empyema
bacteremia
sepsis
what are the signs and symptoms associated with Streptococcus pneumoniae infections?
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
how can you diagnose Streptococcus pneumoniae infections?
- chest x-rays
- PCR test
- urine antigen analysis (test for bacteremia)
- physical examination
how can you treat infections caused by Streptococcus pneumoniae?
Medications:
- antibiotics
* pneumonia = beta-lactam antibiotics
* sinusitis = amoxicillin
Other interventions:
- pneumococcal vaccines
