Streptococci Flashcards
What is the most common entry point for respiratory infection?
it is your respiratory. there is the upper and the lower.
Upper respiratory - nose, nasal, cavity, sinuses, mouth and throat
Lower - trachea, bronchi, bronchioles and alveoli in the lungs
What are the mechanisms of protection of the lungs?
Normal flora alone with nasal hair, nasal turbinates, mucus, involuntary responses, IgA and immune cells
What are characteristics of Streptococci?
Gram positive, non, motile and sporing. Catalase negative. Cocci bead like chains, aerobic and anaerobic.
- posses a M protein and LTA (lipoteichoic acid)
What classifies the C-carb
Beta hemolysis
What are the forms of the the pathogen
A, B,C, F, G
What are the most infectious groups
A and B
What does Alpha hemolytic ID
S. viridans and S. pneumoniae
What does gamma hemolytic ID
Streptococcus and Enterococcus faecalis
What is the overall structure of the cells
it has a cytoplasmic membraane, mucopeptide, Groups Carbohydrate, protein antigens, M-protein- antophagocytic and least 80 different M serotypes.
Protein F binds with fibronectin
Protein F and M protein help in attachment wit the host cells in tissues
Protein g binds with the Fc protein of the antibodies
Capsule- composed of hyaluronic acids that protects again phagocytosis.
What are the toxics of Beta-hemolytic Strep. group?
- Strep O is antigenic and used to diagnosis of Rheumatic fever. (ASO Test)
S- oxygen stable - non-immungoenic, cell bound
O-oxygen labile - hemolysis under anaerobic conditions only.
Erythrogic toxin - responsible for scarlet fever. screened by Dick test. it is injected intradermally.. localized erythema. DPNase, diphosphopyridine nucleotides play a role in the toxins and exotoxin A is the super antigen that deals with necrotizing fasciitis.
What are the enzymes of Beta- hemolytic Strep, group A?
Streptokinase- A and b forms - lyse blood clots
Streptodonase - breaks DNA reducing the viscosity of the pus
Hyaluronidase - spreading factor
C5a peptidase - degrades complemnt component of C5a that attracts phagocytes to the sites of complement deposition and prevents chemotaxis of neutrophils and mononuclear phagocytes
What is SPE
Strepococci pyrogenic exotoxins act as super antigen and responislbe for streptococcal TSS.
What are the sources and modes of spread
Dried secretion, acute sore throat, acute otitis media and nasal carriers.
How does Group A streptococci cause diseases
pyogenic inflammation- cellulitis, impetigo and erysipelas
Exotoxin production - necrotizing fasciitis
immunologic - RF and AGN
What are the indirect pathogenesis
rheumatic fever ( Pain in heart and joints) and Glomerulonephritis ( ultimate kidney failure)
What is the pathogenesis of rheumatic fever
caused by many M serotypes of S. progenies. probable cross reaction between group A antigen and heart tissue. the genetic factors my play a role along with throat infection.
What is the pathogenesis of Glomerulonephritis
cause by M serotypes, repeat infections are rare. usually from a previous throat or skin infection. can be a combination of antigen cross reaction between S. pigeons and glomerular basement and autoimmune process
What are the lab diagnosis and treatment of S. progenies ?
Direct Smear
isolating and culture on blood agar
indirect evidence by antibodies to one or more Strept. enzyme
gram strain
Culture on B/A is a beta hemolysis
Catalase negative
bacitracin senstive- group A strep
High titres of anti-DNasw B
Drug of choice- penicillin, orally or IM
Penicillin allergy - erythromycin
What are Group B Streptococci structure
you will see the diplococcal pairs in short chains. They have polysaccharide capsules contain sialic acid.
What are the types of antigens of group B
Ia, Ib,II,III,IV
What are one of the most important pathogens in the neonate?
Acute fulminating respiratory syndrome and Neonatal meningitis
How do you diagnose Group b Streptococci
CAMP test
middle streak is S. aureus
Perpendicular streak A- S.agalactiae
Perpendicular streak b- S. pyogenes
CAMP factor makes the steak closer to S. aureus more prominent arrow had hemolysis
Group B strepococci is less susceptible to what
penicillin. needs to combined with aminoglycosides to be effective
What are oral streptococci
S. Viridians
