Bacteriology Flashcards
What important bone infection is caused by s aureus?
Osteomyelitis
3 structural pathogenicity factors of s aureus?
Peptidoglycan
Protein A
Clumping factor
3 types of exotoxins produced by s aureus?
Alpha to gamma lysins
TSST
Enterotoxins
What is Panton-Valentine leukocidin and what does it do?
An exotoxin associated with highly virulent s aureus strains incl MRSA
Lyses polymorphonuclear leukocytes
What disease is PVL associated with in kids?
Severe necrotising pneumonia
Suitable antibiotics for MSSA?
Flucloxacillin
Macrolides, aminoglycosides
Suitable antibiotics for MRSA?
Glycopeptides incl vancomycin, daptomycin
Linezolide
What criteria defines B haemolytic streptococci as group A, B, C, D etc.? What does it describe?
Lancefield criteria
The antigens carried on the cell surface
What is the extra cellular enzyme which distinguishes s aureus from other staphylococcus species?
Coagulate
What are 2 examples of common alpha haemolytic strep?
Strep pneumoniae
Viridans group
What do alpha haemolytic strep do to blood on blood agar?
Oxidise the intracellular iron, turning rbcs green
What do beta haemolytic streptococci do to blood?
Completely haemolyse rbcs, leaving clear area on blood agar
What do gamma haemolytic streptococci do to blood?
No haemolysing activity
What are the 3 major groups of beta haemolytic streptococci?
A B D
What is the archetypal group A strep?
Strep pyogenes
What are the 2 major types of virulence factors on strep pyogenes (GAS)?
Streptolysins (O and S)
Streptococcal pyogenes exotoxins (Spe) A and C
What are SpeA and SpeC responsible for?
Rash in Scarlett fever, streptococcal toxic shock syndrome
What is acute rheumatic fever a complication of? Why does it occur?
Strep pyogenes (GAS) infection, usually respiratory M protein generates cross reactive autoAbs to endocardial and synovial tissue
How does acute rheumatic fever most commonly present? How else can it manifest?
As a migratory polyarthritis
Can also manifest as a pancarditis +/- pericarditis
What is rheumatic disease of the heart?
A chronic inflammation of the endocardium (particularly mitral valve) due to previous acute rheumatic fever infection
What is a renal complication of GAS infection?
Post-strep glomerulonephritis
What is an important cause of puerperal fever/sepsis?
Strep pyogenes (GAS)
What complication can GAS cause in new mothers?
Puerperal fever and sepsis
What is the archetypal group B strep (B haemolytic)?
Streptococcus agalactiae
What are the most important manifestation of GBS (strep agalactiae) infection?
Neonatal meningitis, sepsis, pneumonia (and old people)
Miscarriage, stillbirth, PPROM due to colonisation in maternal intestines and female reproductive tract
What have many group D strep been recategorised as?
Enterococci
What are 2 clinically relevant bacteria still classed as GDS?
Strep bovis and strep equinus
2 common species of enterococci commensal in intestines?
Enterococcus faecalis (90%) Enterococcus faecium (10%)
What haemolytic activity do most enterococci have? 2 exceptions?
Mostly gamma haemolytic
E faecalis = sometimes alpha
E faecium = sometimes beta
What are enterococci examples of? How do they respire?
Lactobacilli - facultative anaerobes
4 important clinical manifestations of enterococcus infection?
Diverticulitis
UTI
Endocarditis
Meningitis
What can an enterococci-induced UTI be treated with?
Nitrofurantoin
What are all enterococci intrinsically resistant to?
Cephalosporins and many B lactams + aminoglycosides
What other chronic condition are enterococci thought to be responsible for, due to biofilm formation?
Chronic bacterial prostatitis
3 types of coliforms?
Klebsiella
Enterobacter
Fecal coliforms incl escherichia
