Streptococci Flashcards
Are Streps gram -ve or gram +ve?
+ve
Where are Streps found?
URT
What can Streps cause in young animals?
Septicaemia
Which parts parts do Streps cause disease?
Udder, urinary tract, skin
Are streps haemolytic?
Yes
Which type of enterococci can cause bacteraemia and nosocomial opportunistic infetions in humans and animals?
Vancomycin-resistant
How long are the chains formed by Streps?
Variable
Which type of cocci only form pairs?
Diplococci, esp straight from the animal in pus
Which proteins do Streps have on the surface?
M protein and lipoproteins
Which proteins are immunogenic?
M proteins
What does the Strep capsule prevent?
C3b
What is the capsule made of?
Hyaluronic acid
What happens if no capsule?
Less pathogenic
What do MSCRAMMs do?
Bind to host surface molecules
How are MSCRAMMs anchored to cell wall?
LPXTG motif
What does M protein bind?
Fibrinogen and fibronectin, and Fc of IgG and IgA
What happens if M protein is mutated?
Less virulent
What happens in M protein vaccines?
Only partial protection
How can you predict Strep virulence?
Use M protein as show variability for immune escape
What is C substance?
A cell wall carbohydrate
Why do you use C substance not M protein for Lancefield grouping?
M protein is too cross-reactive
Which letter are the Lancefield groups?
A-N
What Lancefield group are equine Streps?
C
What Lancefield group are most veterinary Streps?
B or C
What do exotoxins mediate the change between?
Non-motile resp pathogen to motile systemic
What do haemolysins do?
Streptolysins S and O (anaerobic vs aerobic) and form pores in cell membranes
What type of haemolysis do all equine pathogens show?
Beta
What kind of haemolysis do non-pathogenic Streps show?
None
What do superantigens cause?
An unregulated T cell response
What do Strep cultures look like?
On blood agar and 37 degrees, facultatively anaerobic, small colonies, mucoid if capsulated, matt if non-capsulated
Are they catalase -ve or +ve?
-ve
How many sugars do equine streps ferment?
At least one, other than S equi
What are the 4 types of genome fingerprinting you can do?
Genome-wide (PFGE), large sub-genomic fragments (RFLP), sequences from sets of genes (MLST), sequences from single genes (SLST)
Where is the reservoir for Streps?
Animals
How long do Streps survive in the animal?
4-5 days
How are new infections acquired?
Inhalation, fomites, direct transfer
Where are neonatal infections from?
Dam
What is the pathogenesis of Strep infections?
Adhesion to resp epithelium, colonisation of epithelium, invasion into lamina propria, evasion of phagocytosis, spreads into circulation and lymphatics, infections of remote organs
What does recovery of Strep infection involve?
Phagocytosis (opsonising antibody)
What is immunity like after recovery?
transient and variable because of M protein variation
What is cross protection between serotypes like in Streps?
Little
