Strep Flashcards
All strep, except 1, are?
GPC in chains
GAS colonies are?
beta hemolytic
Skin and tissue infection of Strep pyogenes?
Impetigo, cellulitis, erysipelas,
Type of cellulitis on skin, esp. on face and leg
erysipelas
Skin infections may be accompanied by?
Scarlet fever
GAS
Skin rash due to erythrogenic toxin?
Scarlet fever
GAS
(streptococcal gangrene, invasive cellulitis, “flesh- eating bacteria”)
Necrotizing fascitis
characterized by the rapid destruction of muscle and fat tissue with high fever and prominent pain; highly invasive and life threatening
Necrotizing fascitis
Treatment for necrotizing fascitis
IMMEDIATE AND QUICK, Aggressive antimicrobic therapy (penicillin) and surgical intervention (debridement of affected tissue to remove toxin)
Also called Streptococcal Toxic Shock Syndrome
BUT
Doesn’t have the TSS toxin
nectrotizing fascitis
Sudden onset of fever, sore throat, and exudative tonsillitis or pharyngitis with enlarged and tender cervical lymph nodes
Acute exudative pharyngitis
2-4 days incubation
Symptoms last a few days (3-5) without antibiotic treatment
Predominantly occurs in children 5-15 years of age and during the colder months (transmission easier due to the effect of crowding and to dry nasal passages)
Acute exudative pharyngitis
approximately 20% of sore throats cultured
Major problem is the possibility of post-streptococcal complications
Acute exudative pharyngitis
autoimmune reaction of Ag-Ab complexes on the basal membranes of the affected organs [No live bacteria in heart or kidney tissue.] – Specific antigenic types are responsible.
Post streptococcal complications
Rheumatic fever
Acute glomerulonephritis
Post streptococcal complications
Most sore throats are viral, but “strep” throat is actually life threatening
due to post-strep complications
Ag-Ab complexes attack heart tissue – specific antigenic types; especially follows throat infections
Rheumatic fever
Ag-Ab complexes attack kidney tissue – specific antigenic types; usually follows throat or skin infections
Acute glomerulonephritis
GAS virulence factors
Numerous invasive enzymes/toxins
Hyaluronic Acid Capsule
Cell wall M protein
Erythrogenic toxin
Streptolysin O/S
Cell wall “M” protein is?
antiphagocytic
cytotoxic; basis of ASO titer and related tests
Streptolysin O and S
appears similar to “self” Ag to host defenses – slow Ab response
Capsule of hyaluronic acid
Antigen detection / identification for GAS…
Direct throat swab has ___ sensitivity
Culture confirmation is ___ accurate
low
very
Antimicrobic susceptibility tests usually not needed
Can typically treat empirically
Generally susceptible to penicillin
Causes pneumonitis and meningitis in neonates due to inoculation from vaginal flora; infection can be quite severe in newborns and leave permanent damage or cause death
Group B Streptococcus
Expectant mothers are screened around 35th week to determine if bacteria are present
Group B Streptococcus
Gram-positive coccus in pairs
Large, mucoid, alpha-hemolytic colonies
Multiple antigenic types (>90); about 6 are frequently recovered and highly infectious
Streptococcus pneumoniae
Normal flora of upper respiratory tract in 30 to 60% of population (esp. when children are in the household). Infection usually results from transmission of normal flora into adjacent sites.
Streptococcus pneumoniae
Lobar and bronchial pneumonia (#1 cause)
Streptococcus pneumoniae
Large, mucoid, alpha-hemolytic colonies
Streptococcus pneumoniae
Invasive strains may lead to empyema, bacteremia, and/or meningitis
Streptococcus pneumoniae
Causes 50-90% of pneumonias; esp. in children under 5 yr and elderly
Mortality: about 5-10%; esp. in children under 5 yr and elderly
Strep. pneuminiae can also cause?
sinusitis
otitis media
meningitis
*Antiphagocytic capsules
IgA protease
Invasive strains
Increase in penicillin resistance
Strep. pneumoniae virulence factors
Strep. pneumoniae virulence factors
Antiphagocytic capsules
IgA protease
Invasive strains
Increase in penicillin resistance
Laboratory diagnosis
Culture (alpha hemolytic) and biochemical identification
Antigenic identification from cerebrospinal fluid
Lab diagnosis strep. pneumoniae: antigenic ID from ____ fluid
cerebrospinal
Other streptococci of occasional pathogenicity
mostly in Groups C, F, G
dysgalactiae, anginosus
beta-hemolytic
a group of alpha-hemolytic and non- hemolytic species associated with various low-frequency diseases (abscesses, bacteremia & endocarditis, dental caries, etc)
Viridans streptococci (this is not a species name)
opportunistic infection
Gram-positive cocci in chains (formerly a member of group D Streptococcus)
Enterococcus faecalis
(1) Frequent cause of nosocomial infections - surgical wounds and urinary tract
(2) Occasional cause of bacteremia (~9%)
Enterococcus faecalis
Multi-drug resistant strains exist with increased frequency, including vancomycin resistance (Vancomycin Resistant Enterococcus = VRE)
