Streptococcus species Flashcards
examples of strept species - 5
- pyogens
- agalactiae
- pneumonaie
- viridans
- anginosus
microbial overview of streptococci 2x SFOC
- gram positive cocci
- grow in pairs/ chains
- some have capsules which can be seen on the gram stain
- facultative anaerobes
- often require blood plasma for growth
- classified into lancefield and hameolysis on agar
haemolysis pattern on blood agar
- alpha - incomplete haemolysis - green tinge
- beta - complete haemolysis = clearing of blood agar surrounding the colony
- non = no change around colony
polysaccharide antigen
helps identify group A,B,C,F,G streptococci
lipotechichoeic antigen
helps classify group D streptococci and enterococci
what technique is used for lancefield
commercial latex agglutination technique
- allows rapid detection of clinically important strep group
beta haemolytic strep
- pyogens
- agalactiae
natural habitat of the strep spp - 5
- pyogens = aysptomatic carriage, common in children = pharynx
- agalactiae = commensals of the gut and female genital tract
- pneumoniae = asymptomatic carriage = URT
- viridans = commensals of the orophyranx
- enterococci = commensals of the large intestines
non invasive infections by pneumoniae - POCS
Pneumonia
Otitis media
Conjuctivitis
Sinusitis
more on the streptococci shape
- lancet shaped cocci
- seen as pairs of cocci - diplococci
- can be single or short chanins
alpha haemolytic strep
- pneumoniae
- viridans
invasive infections by pneumoniae - BEMPS
Bacteriamia
Endocarditis
Meningitis
Peritonitis
Septic arthritis
(ASS)
Pathogenesis of S pneumoniae
Virulence factors of S pneumonaie - 5
- Capsule
- Cell wall polysaccharide
- Autolysin
- Pneumolysins
- Pneumococci surface proteins
pathogenesis of pyogens
-TSIB
- CISAT
(just like neterobacterales)
somatic pyogens virulence factor - 5
- Hyaluronic capsule
- M protein to ptevent intraellular killing nand phagocytosis
- Sreum opacity factor
- Lipotechichoiec
- Fibronectin binding factor
Extracellular products - 7
- hyaluronidase - break down ctd tissue for spread into adjacent tissue
- streptokinase - breakdown fibrin clot for spread
- DNAses - A-D
- C5a peptidase inactivates the C5 complement protein
- streptococcal pyrogenic exotoxins = for pathogenesis of TSS
- Streptolysin S - lysis of a variety of cells
- Streptolysin O - lysis of cells including rbc’s so plays a role in b heamolysis
what does strep agalactiae also colonize?
vagina, urethra of both males and females and the git
diseases caused by strep pyogens
pathogenesis of GBS neonatal infection
Diseases caused by S. agalactiae - 4
- postpartum infection and neonatal spesis = caused by an underlying abnormalities
- bacteraemia = common in adults
- Early neonatal sepsis = hours to days. Associated with pneumoniae and bacteremia, rarely meningitis
- Late neonatal spesis = days to months. Associated with bacteramia and meningitis
