Streptococci Flashcards
(26 cards)
What are key characteristics of Streptococci?
Gram Positive cocci arranged in pairs/chains, faculative anaerobic, lactic acid production/fermentation
Catalase Negative
What organism is Group A strep?
S. Pyogenes
What is organism Group B?
S. Agalactie
What are differences between the hemolytic patterns?
alpha - partial hemalysis - green colored
beta - complete clearing
gamma - no change/minimal
What are common infections for Group A strep?
soft tissue, skin, and pharyngitis
What does Strep Group B commonly cause?
Neonatal diseases
What is the structure of S. Pyogenes?
M surface Proteins, Hyaluronic Acid Capsule, C5a peptidase. Group A.
How does S. Pyogenes avoid the immune system?
Capsule preventing phagocytosis
M-like proteins block C3a and bind Fc regions of antibodies preventing opsonization
C5a peptidase preventing complement
What is key in S. Pyogenes ability to invade the cell and adhere?
Surface protein M
What are kinds of Toxins produced by S. Pyogenes?
Spe toxins - superantigens, which are key to rapidly spreading infection in necrotizing fascititis due to the amplified immune response.
Also streptolysin, strepokinase, and DNAse
~All help mediate the spread of the infection
What type of patients have highest incidence of S. Pyogenes?
Children between 5-15 year old. Once developed an antibody to surface protein M the individual is protected.
How is S. Pyogenes transmitted?
Typically by droplet. Can colonize the pharynx without any symptoms.
What are illnesses associated with S. Pyrogenes?
Strep Pharyngitis, Scarlet Fever, Impetigo, Erysipeles, Strep Toxic Shock, Endocarditis (MURMURS), and necrotizing fasciitis (due to immune response).
What are late/after effects of a Strep infection?
Rheumatic Fever - from strep antigens being cross reactive to heart tissue and joint tissue and immune system attacks them
Glomerulonephritis - follows pharyngitis and skin infection and antibodies attack basement membrane of kidney
What would cultures identify about S. Pyogenes?
Gram Positive cocci in chains, catalase negative, group specific carbohydrates, and susceptible to bacitracin
What bacterium is Group B strep and where does it reside?
S. Agalactiae and is typically found in the GU and GI tracts. Has Capsule.
What can typically cause both early and late onset meningitis in new borns?
S. Agalactiae. Mothers can pass it on to the children as well and they should be treated before giving birth.
What are the physical characteristics of S. Pneumonia?
Gram Positive, encapsulated oval cocci in pairs/chains, Alpha-hemolytic, unique cell wall of Teichoic Acid, C-polysacchride and F-antigen
How does S. Pyrogenes compare to S. Pneumonia?
S. Pneumonia doesn’t produce toxins and is invasive due to the host’s immune response.
What is the unique pathogenesis of S. Pneumonia?
Adherence to epithelial cells, capsule resists phagocytosis, and releases cell wall components to cause inflammatory response allowing migration of the bacterium.
What parts of the S. Pneumonia cell wall are important?
Teichoic Acid, Peptidoglycan, and Pneumolysin activate complement and inflammation response.
How does S. Pneumonia typically infect people?
Part of natural flora in upper airway, but if gets into lower airway can colonize and if protective mechanisms are lacking in the lower airway.
What kind of infections can S. Pneumonia cause?
Lower lobe pneumonia, otitis media/sinusitis, and has a high likelihood of spreading once in lungs.
What is key to having an antibody against to prevent S. Pneumonia?
Anticapsular antibody protects the individual
