Bacterial Pharyngitis
Streptococcus species classification 3rd level
3rd level: DNA sequence similarity
3 mechanisms of disease for strep pyogenes
1) pyogenic inflammation (pharyngitis) 2) Exotoxin production -widespread systemc symptoms (scarlet fever) 3) immunologic -ab against organism cross react with host tissue. (rheumatic fever, joints , skin, spinal cord, brain) 2-3 weeks after strep infection
Pharyngitis caused by strep pyogenes diagnosis
1) throat culture on blood agar 2) gram stain 3) rapid antigen detection test Detects group A carbohydrate antigen 60-90% sensitive 98-99% specific
Streptococcus species classification 1st level
1st level: hemolytic pattern (not just for strep) -Partial (alpha) -complete (beta) -gama (no damage to RBCs)
Streptococcus species classification 2nd level
2nd level: group determination done via antibody testing serologic properties: -lancefield groupings (A-U)
characteristics of M protein
Adhesin that binds fibronectin antiphagocytic: bind complement factor H and destabilises C3b antigenic: you can establish M protein antibodies but there are however 80 types of M Protiens
Pathogenisis of diptheriae
Diphtheria toxin inhibits protein syntesis by ribosylation of EF2 endcoded by phage systemic spread very potent very stable
Streptococcus species gram shape metabolism catalase can they be normal flora virulence factors
Diverse gram positive cocci most are facultative anaerobes catalase negative Can be normal flora adhesins and toxins
Describe the group and hemolytic nature of: Habitat diseases S pyogenes
Group A Beta hemolytic Throat skin pharyngitis, impetigo, necrotizing fasciitis, rheumatic fever, glomerulonephritis
Describe the group and hemolytic nature of: S. agalactiae Habitat diseases
Group B Beta hemolytic female genital tract neonatal sepsis and meningitis
Describe the group and hemolytic nature of: S. bovis
Group D alpha or gamma colon endocarditis
Describe the group and hemolytic nature of: S viridans
None alpha or gamma mouth, throat, colon, female genital tract dental caries, endocarditis, abscesses
Specific bacteria that cause pharyngitis
Streptococcus pyogenes (group A beta hemolytic) (casues 30%) corynebacterium diphtheriae haemophilus influenzae (type B) neisseria gonorrhoeae
Quickly describe the rapid strep test procedure
antibodies to Group A carbohydrates mixed with sample and if present will bind to group A. On est strip you have the same antibodies and will cause Strep A to bind to the strip. the free antibodies already bound to Group A will cause a purple line on the test strip
virulence factors Protein F M protein Capsule hyaluronidase streptokinase Dnase
binds fibronectin (attachment) binds fibronecting (attachment) (inhibits complementation) adhesin that inhibits phagocytosis (attachment/growth) inhibits phagocytosis (growth) degrades hyaluronic acid (spread) activate plasminogen (spread) Degrades DNA in nectrotic tissue and pus (spread)
Scarlet fever Caused by dead give away rash
caused by pyrogenic toxin "strawberry tounge" dead giveaway rash: -12-48 hours after fever that usually starts on the chest and fades in 3-4 days then skin peals
What does catalase do?
converts hydrogen peroxide into oxygen and water
cornybacterium diptheriae description spores? host range infection where?
gram positive rod that is club shapped non spore forming humans are only host infection in throat causes diptheria
Clinical findings and lab diagnosis treatment
thick grey pseudomombrane over tonsils and throat throat culture and PCR for toxin gene Treatment via penicillin and antitoxin (horse Ab)
What is pharyngitis symptoms What percent caused by bacteria
inflammation of the oropharynx sore throat, fever, malaise, pain, cervical lymphadenopathy (20% assymptomatic) only 30% caused by bacteria
Diseases that can be caused by streptococcus pyogenes
meningitis sinusitis pharyngitis Acute rheumatic fever pneumonia impetigo necrotizing fasciitis osteopmyolitis acute post-streptococcal glomerulonephritis
S pneumoniae
no group alpha hemolytic throat pneumonia, meningitis, endocarditis
Toxins streptolysin O streptolysin S Pyrogenic exotoxins A,B,C Exotoxin B
oxygen-labile hemolysin (antigenic) oxygen stable hemolysin (nonantigenic) superantigen (toxic shock and scarlet fever) destroys tissue (necrotizing fasciitis) Amounts vary by species and are not present in all
Streptococcus pyogenes Mechanism of spread
person to person
Rhematic fever cause on set symptoms Treatment
serious post infection sequela antibodies that cross react to heart tissue antigens (anti M-protein Ab) onset 2-3 weeks after infection symptoms: fever, malaise, migratory poly arthritis, heart damage can be reactivated by subseequent S pyogenes infections treatment with penicillins