Gram Positive bacteria Flashcards
Symptoms of Staphylococcus Aureus infection
- Shoulder pain
- Pyrexia
- MRI scan shows disc infection and osteomyelitis C6 + C7
What is osteomyelitis
Bacterial Infection of the bone causing weakness
How is infection with staphylococcus aureus treated
With flucloxacillin for 3 months
What is flucoxacillin
Antibiotic
How many species of staphylococcus are there
40
What can staphylococcus be divided into
Coagulase positive or negative
What is a coagulase
Enzyme produced by bacteria that clots blood plasma.
Advantage of a bacteria being coagulase positive
The fibrin clot formed around the bacteria may protect from phagocytosis
Why are some strains of staphylococcus coagulase -ve
They can attack in opportunistic infections
Where are staphylococcus usually found
Nose and skin
How is staphylococcus. aureus spread
Aerosol and touch
What is MRSA resistant to
- Beta-lactams
- Gentamicin
- Erythromycin
- Tetracycline
What are four virulence factors that are released by staph. aureus
- Pore-forming toxins
- Proteases
- Toxic Shock Syndrome Toxin
- Protein A
Name the pore-forming toxin produced by staph. aureus
Alpha-haemolysin and PVL
Name the protease released by staph. aureus
Exfoliatin
How does TSST effect the body
Stimulates cytokine release
What is protein A
Surface protein that binds Igs in the wrong orientation
What three associated conditions with coagulase negative gram positive bacteria
Endocarditis
Septicaemia
Infected imlants
What are some associated conditions with pyogenic bacteris
- Wound infections
- Abscesses
- Septicaemia
- Pneumonia
- Endocarditis
- Osteomyelitis
What are three associated conditions with toxin-mediated bacteria
- Scalded skin syndrome
- Toxic shock syndrome
- Food Poisoning
Name two coagulase-negative staphylococci
S. epidermidis
S. saprophytic
Where are S. epidermis commonly found
Infections in debilitated catheters and prostheses (remember, these are opportunistic bacteria as they are coagulase -ve)
What do S. saprophyticus cause
Acute cystitis
How does S. saprophyticus cause infection
Produces urease which -> kidney stones
Haemagglutuinin for adhesion
What symptoms are associated with Streptococcus progenies
Fever
Malaise
What would I see in an agar plate if Strep. progenies is found
- Beta-haemolytic (causes lysis of red cells around the colony)
- Facultatively anaerobic
- Penicillin sensitive
What is alpha haemolysis
Partial haemolysis (H202 reacts with Hb)
What bacteria causes partial haemolysis
S. intermedius
What is Beta haemolysis
Complete lysis
What is gamma haemolysis
No lysis at all
What three ways can streptococci be classified as
- Haemolysis
- Lancefield typing
- Biochemical properties
What is lance field grouping
A method of grouping catalase negative, coagulase negative bacteria based on bacterial carbohydrate cell surface antigens
Describe how lance field grouping is carried out
Antiserum is added to each group of suspension of bacteria
1. Clumping indicates recognition
What infections are caused by S. progenies
- Wound infections causes cellulitis
- Tonsillitis + pharyngitis
- Otitis media
- Impetigo
- Scarlet fever
- Complications
- rheumatic fever
- glomerulonephritis
What factor does S. progenies release
Hyaluronidase for spreading
Streptokinase - breaks down clots
C5a peptidase - reduce chemotaxis
What toxins are released by S. progenies
Streptolysins O + S - binds cholesterol
Erythrogenic toxin - SPeA t ogive exaggerated response
What surface receptors do S. progenies have
Hyaluronic acid on capsule for protection
M proteins which encourages complement degradation
Symptoms of S. pneumonia
- Nasal congestion
- Fever
- Severe pain in chest
- Blood + sputum in culture
Why are S. pneumonia found as draughtsman colonies
Flattened, depressed centre in colony
Where does the colony of S. pneumoniae start at
Oropharynx (30% of pop)
What does S. pneumonia cause
Pneumonia, otitis media, sinusitis, meningitis
What three factors can predispose you to S.pneumoniae infections
- Impaired mucus trapping from viral infection
- Hypogammaglobulinaemia
- Asplenia
What makes the S. pneumonia inflammatory wall
- Teichoic acid
2. Peptidoglycan
What cytotoxin is produced by S.pneumonia
Pneumolysin
When are polyvalent vaccines to S.pneumoniae given
Those older than 2 who are at risk of infection
