0516 - Streptococcus pyogenes - EG Flashcards
Commensal flora tends to inhabit the?
skin and mucous membranes
What is the primary difference between resident and transient flora?
resident flora inhabits body sites for extended periods of time and re-establishes when disturbed, transient flora only inhabits body sites for short periods.
what are endogenous pathogens?
those that are part of the resident or transient normal flora, but become pathogenic under certain conditions.
What are exogenous pathogens?
those that are never part of normal or commensal flora, therefore always pathogenic when present. Such as mycobacterium tuberculosis, Neisseria gonorrhoea
Should normal pathogens be found below the level of the carina?
No.
What are normal flora of the upper respiratory tract?
Streptoccus, staph, candida
What microbes are part of normal flora of the mouth and teeth? What diseases can they cause?
Agents: anaerobes, streptococcus viridans, candidaDiseases caused: gingivitis, tooth abscess, oral thrush
What is a cause of endocarditis?
Normal flora such as those from the mouth and teeth disseminating into the blood to the heart.
What are some normal flora of the throat?
Strep. pyogenes most common, also S. pneumonia, H. influenza, S. aureus
What can cause bacteraemia or meningitis?
Dissemination of normal throat microorganisms, such as S. pneumonia, H. influenza.
What are some properties of bacteria used to classify them as a species?
morphology - Gram stain and colony appearancephysiology - environmental conditions under which growMetabolic activities - substrates utilised and by-products produced.
How does Strep. pneumonia grow differently to Strep. viridians as seen in gram stain?
Strep. pneumonia tends to appear as diplococcic, compared to Strep. viridans as cocci in chains.
How are bacteria classified in accordance to there growth in oxygen?
Aerobe - requires oxygenAnaerobe - grows without oxygenstrict anaerobe - will die in the presence of oxygenobligate anaerobe - will grow in a small amount of oxygenFacultative anaerobe - grows either in/out of presence of oxygen
What species of Streptococcus are beta haemolytic?
pyogenes and agalactiae
What species of Streptococcus are alpha haemolytic?
virdans and pneumoniea
What streptococcus species are gamma haemolytic? What is another species (not Strep.) that is gamma haemolytic?
bovis and some viridans.Enterococcus
What is the species known as Group A Strep?
pyogenes
What is the species known as Group B Strep?What is a common disease caused by it?
agalactiae.Neonatal sepsis
What is the species known as Group C and G Strep?What is a common disease caused by it?
dysgalactiaepharyngitis, cellulitis
What is the species known as Group D Strep?What is a common disease caused by it?
bovisbacteraemia, endocarditis
What is the most common cause of bacterial meningitis?
Strep. pneumoniae
What is the most common cause of abscess formation?
Strep. milleri.
What is the most common cause of dental caries?
Strep. viridans
Where are enterococcus species predominantly found?
In the bowel.
what does pyus stand for?
Pus
Where is strep. pyogenes predominantly found?
throat and skin
What are 5 virulence factors of bacterial pathogens?
adhesinsinvasinsimpedinsaggressinsmodulins
Bacteria can be classified according to the temperature they grow best in. What are microorganisms that grow between 14-45 degrees Celsius known as?
mesophiles
What are the main adhesins of S. pyogenes?
proteins, lipoteichoic acid
In the strep. pyogenes strains that have a capsule, what is it made of and what function does this enable?
hyaluronic acid, resembles hose so aids to hide from immune response. Also aids hiding PAMPs, such as peptidoglycans and lipotechoic acid.
How does the M-protein of Strep. pyogenes act as a virulence factor?
Both as an adhesion and a impedin.Inhibits complement activation.
What are the functions of the S. pyogenes aggressins?
destroy tissue to enable bacteria to spread
What are the aggressins that are used in diagnosing S.pyogenes infection?
Antibodies are made against the DNAses and can be used to detect infection. Streptolysins O.
What are the main infections associated with S. pyogenes? What diseases are as a result from its exotoxins? What diseases result post-infection?
pharyngitis, skin infections (impetigo, erysipelas, cellulitis, ), bacteraemia.Exotoxins: Scarlet fever, toxic shock syndrome, necrotising fasciitis.Post-infection: glomerulonephritis, Rheumatic fever.
Cellulitis can not only be caused by strep. What are some other causes?
animal bites, water exposure, longstanding skin ulcers, trauma.
What are the effects of super antigens?
Normal antigens do not elicit a vast T cell response, whereas super antigens activate a greater amount of T cells, resulting in the production of a massive amount of cytokine that results in extreme vasodilation, hypertension, and eventual organ failure/
What is the cause of S.Pyogene related glomerulonephritis?
Antigen-antibody complexes lodge in the glomeruli of the kidneys, resulting in inflammation. Can lead to kidney failure
What is the pathophysiology behind rheumatic fever?
M protein mimics heart muscle, such that M protein antibodies cross-react with and damage heart.
