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Bateria Pathology and Medical
Exam 2 Microbiology (Medical)
44
Science
Graduate
11/10/2007

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Cards

Term
Group A Strep genome size?
Definition
Small
Term
Streptococcus pyogenes
Definition
Group A streptococcus
Term
Streptococci (Morphology and Physiology)
Definition
  • Anaerobes : Facultative
  • Limited metabolism
  • Catalase negative
  • 29 species
Term

Streptococcus

Lancefield typing scheme

Definition

Detect specific sugar with antisera 

Group A: rhamnose-N-acetylglucosamine (Streptococcus pyrogenes)

Group B: rhamnose-glucosamine (Streptococus agalactiae)

Group A, B, C, F, and G (Streptococcus anginosus)

Not classified:  Streptococcus pneumoniae)

Term

Streptococcus pyrogenes

Habitat and Transmission

Definition

Habitat:  Human pharynx, skin, musocal surfaces

Transmission: droplets or direct contact

Term
Group A serotyping
Definition
  • Antigenic variation of the M Protein
  • More than 150 antigenic types: M1, M2, etc
  • Antisera to various M types
  • Determine emm sequence
  • Certain M types associated with specific outcomes of infection
  • Class I: pharyngeal & invasive
  • Class II: skin, non-specific
Term
Virulence Factors of Strep Pyrogenes
Definition
  • M Protein
  • Polysaccharide Capsule
  • Bunch of Exoproteins!
  • Amylase
  • Streptolysin O, S
  • SPE B (Cysteine protease)
  • Glucuronidase
  • SPE A, C
  • Mitogenic factor (DNase B)
  • DNase A, C, D
  • Bactericins
  • Phosphatase
  • Streptokinase
  • Serum inhibitor of complement
  • Leucyl aminopeptidase
  • NADase (ADP=ribosylase)
  • Autolysins
  • Enterotoxins
Term

GAS Virulence Factor: M protein

Definition
  • alpha-helical, coiled-coiled
  • Antiphagocytic (binds human proteins)
  • Factor H, C4b - inhibit complement activation
  • IgA-Fc
  • others
Term
GAS Virulence Factors:  Polysaccharide Capsule
Definition
  • Inhibits phagocytosis
  • Composed of hyaluronic acid
  • Identical to that found in  human tissue (molecular mimcry).  Not antigenic
Term
GAS's SpeB
Definition
Remodels bacterial cell surface proteins
Term
Diverse outcomes of infection of GAS
Definition
  • Asymptomatic: .5-4%
  • Pharyngitis or "Strep throat" 5/1000
  • Impetio
  • Erysipelas
  • Scarlet Fever (Strawberry tongue)
  • Toxic shock syndrome - 3,000 cases in US/year
  • Necrotizing fascilitis
Term
GAS Suppurative infections
Definition
  • Pharyngitis
  • Scarlet Fever
  • Toxic Shock syndrome
  • Skin Diseases
Term
GAS Nonsuppurative sequelae
Definition
  • Acute rhematic fever (Heart disease/Arthritis/OCDs)
  • Acute glomerulonephritis
Term
Acute glomerulonephritis
Definition
  • Post infection sequelae (pus)
  • Immune complex -> inflammation
  • Glomerulonephritis
Term
Pediatric Autoimmune Neuropsychiatri Disorders Associated wih Streptococcal infections: PANDAS
Definition
  • Sydenham chorea
  • Post-infection sequelae
  • Tourette's syndrome , tics, obsessions (OCD)
  • Immune sequelae of GAS aby's attach basal ganglia
Term
GAS Diverse outcomes of infection
Definition
  • Impetigo
  • Scarlet Fever
  • Erysielas
  • Pharyngitis
  • PANDAS
  • Rheumatic fever
  • Glomerulonephritis
  • Toxic shock syndrome
  • Necrotizing fasicilitis
Term
GAS: Discovery of the Pan Genome when 12 genome sequences were published
Definition
Which is composed of a "core genome" containing genes present in all strains, and a "dispensable genome" containing genes present in two or more strains and genes unique to single strains. Given that the number of unique genes is vast, the pan-genome of a bacterial species might be orders of magnitude larger than any single genome.
Term
GAS Intraspecies genetic variation
Definition
  • 12 complete genome sequences of GAS
  • >85% genome sequence is conserved among 12 strains (core genome)
  • Pan Genome - 2,500 genes
  • Elements of the pan genome likely to contribute to variability in the outsomes of infection
Term
GAS Variable genome elements
Definition
  1. Prophage
  2. Integrated conjugative elements (ICE)
Term
Mobile Elements of GAS are similar to:
Definition
  1. Staphyococci
  2. Enterococci
  3. Clostridia
  4. Streptococci

THE GENOME IS PLASTIC

Term

GAS

What caues change in expression?

Definition
  • Stability of transcriptome (difference during in vitro culture) suggests a stable genetic change
Term

GAS

Invasive transcriptome associated with covS mutation

Definition
  • All pharyngeal profile colonies/isolates: covS+
  • All invasive colonies/isolates: covS-
  • PERFECT correlation between covS allele and invasive transcriptome profile
Term

GAS

Why do invasive variants acquire mutations in covS?

Definition
  • Trigger for invasive disease (covS- -> No SpeB (degrades SKA))
  • In the absenc of SpeB, human plasmin accumulates on bacterial surface, which contributes to the invasive phenotype
Term

Neutrophils critical in limiting infection

Definition
  1. Ways to kill baceria
  2. Phagocytosis
  3. Antimicrobial peptides
  4. Reactive oxygen etc.
Term

GAS

NET

Definition
Neutrophil Extracellular Traps
Term
S. Pyrogenes secretes DNase's
Definition
  • DNase A,B,C,D
  • SdaB = Mitogenic Factor/SpeF:  only chromosomally encoded DNase
  • Streotidirnase 1 (Sda1) encoded by a prophage associated with current episodes of invasive infection
Term
Sda1 and selective pressure for CovRS mutations:  mechanism of invasion?
Definition
  • Sda1 degrades NETS -> Contributes to viability of organism
  • SpeB -> degrades Sda1
  • Acquisition of Sda1-containing prophage puts selective pressure (via neutrophil survival) on the accumulation of covRS mutations to abrogate speB expression
  • The mutations are associated with an invasive phenotype and hence the increase in invasive disease episodes since the global disseminatin of M1 clones
Term
Model for Streptococcal Invasive Disease
Definition
  1. Entry SpeB
  2. Mutation in CovRS
  3. DNA NET destruction
  4. Invasion
Term

GAS

Control

Definition
  • B-lactams:  100% susceptible, 35% clinical failure rate
  • Intracellular reservoir
  • B-lactamse producing normal flora
Term
GAS Vaccine Development
Definition
  • M protein
  • C5a peptidase
  • SpeB
Term
Gram Positive Cocci
Definition

Catalase + Staphylococci (grows in clusters)

- Streptococci (grows in chains)

Term
Hemolysis patterns on Blood agar
Definition
  • beta-hemolytic- Groups A, B, C, F, and G (typed using Lancefield grouping system)
  • alpha-hemolytic - Streptcoccus Viridans group an dStreptococcus pneumoniae
  • gamma-hemolytic - Group D Streptococci and Enterococci
Term
Beta-Hemolytic Streptococci - Lancefield grouping
Definition
  • Group A (Streptococcus pyrogenes): Rhamnose-N-acetylglucosamine polysaccharide
  • Group B (Streptococcus agalactiae):  Rhamnose-glucosamine polysaccharide
Term

Group B streptococci

S. agalactiae

Definition
  • Major cause of disease in neonatal and perinatal periods
  • Early onset (Ascending infecion in utero, ruptured fetal memmbranes, passage through colonized birth canal)
  • Late onset (Nosocomial infection)
Term

Group C and G Streptococci

S. dysgalactiae

Definition
  • Groups C and G associated with pharyngitis, but generally not sequellae seen with Group A streptococci
  • Compromised hosts - Deep abscesses, bacteremia
Term
Streptococcus viridans
Definition
  • Large group of alpha-hemoltic streptococci- part of the normal flora of the upper respiratory tract
  • 30-40% of all cases of aubacute bacterial endocarditis - Associated with dental procedure
  • Penicillin resistance
Term
Streptococcus pneumoniae
Definition
  • Community acquired pneumoniae (CAP)
  • Adult menigitis
  • Sinusitis, otitis media
  • Bacterimia
Term
Optichin
Definition
  • Optichin susceptible = Streptococcus pneumoniae
  • Optichin resistant = Other alpha-hemolytic Streptococci
Term
Pathogenesis of pneumococcal pneumonia
Definition
  • Two types - Opaque and transparent (transparent (no capsule) binds nasopharyngeal region))
  • Immunity is due to specific anti-capsular antiboides
  • Infection develops as a result of aspiration of nasopharyngeal secretions (Extremes of age, smokers, COPD, Decrease in ciliary activity)
Term

Pathogeness of penumococcal pneumonia

Definition
  • Capsule is anti-phagocytic
  • Inflammation in lung is due to cell wall components: teichoic acid and phosphorylcholine
  • Extensive tissue damage causes fluid accumulation and PMN recruitment
  • Pneumococci use the fluid as a growth medium and serves to move the organism to other areas of lung and beyond
Term
Pathogenesis of pneumococcal pneumonia
Definition
  • Red hepatization - endothelium is damaged and RBC's are lost in tissue
  • Grey's hepatization - Extensive PMN recruitment and fibrin deposits - antibody is produced (beginning of recovery)
  • Organism can escape and seed the blood and meninges
Term

S. Pneumonia

Virulence Factors

Definition
  • Polysaccaride capsule (Over 80 different types, anti-capsular antibody is protective)
  • PspA-Cell wall protein-protection against host complement
  • Hyaluronidase - Degrades extracellula matrix - Important in pneumococcal pneumonia
  • Pneumolysin-cytotoxic to ciliated bronchial epithelial cells - slows cilary beating.  Cytoplasmic enxyme - works in concert with LytA autolysin
  • Pneumococcal surface antigen - Mn and Zn transporter
  • Neurominidase - Important in otitis media pathogenesis - cleaves mucin found in eustachian tube
Term

S. Pneumonia

Naturally competent

Definition
  • Naturally competent for a small period of time early in exponential growth

 

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