STREPTOCOCCUS
&
ENTEROCOCCUS
REVIEW
Bacterial Cell Morphology
•
•
•
•
Gram Stain
Cytoplasmic (plasma) membrane
Cell wall structure
Bacterial cell shapes
Common Cell Membrane
Gram-Positive Cell Wall
Peptidoglycan
GramNegative
GramPositive
Gram-Positive Cell Wall
Teichoic Acid
Gram-Negative
Cell Wall
Gram-Negative Cell Wall
Genus Streptococcus
Commensals or Parasites of man & animals
or
Saprophytes of decaying matter
Morphology
Gram-Positive Cocci in Pairs or Chains
Gram-Positive
Streptococcus
Genus Streptococcus
Physiology & Metabolism
Facultative Anaerobes
Fastidious Growth Requirements
Fermentative Metabolism of Carbohydrates:
Lactic acid, ethanol, acetate endproducts produced; No gas
Catalase Negative (2H2O2 ---> O2 + 2H2O)
Separation of streptococci from staphylococci
Oxidase Negative (oxidoreductase oxidizes substrate w/ O2)
Beta, Alpha, or Gamma Hemolysis on blood agar
Genus Streptococcus
Rebecca Lancefield
Developed useful serogrouping system
Classification of beta-hemolytic streptococci by
group-specific cell wall carbohydrate (CHO) antigen
As of 1992, Serogroups A to H and K to V
Groups A, B, C, D, and G are most
comonly associated with human disease
Viridans streptococci and
Streptococcus pneumoniae have
no group-specific antigen
Antigenic Structure
Streptococcus pyogenes (Group A)
Lancefield Group-specific antigen (C polysaccharide)
Complex polysaccharide in cell wall
Proteins: Two major classes, M & T antigens
Two minor classes, R & F
M-Protein: Type-specific antigen
Fimbriae-like, hairy extensions
Resistant to heat and acid
Trypsin Sensitive
Specific adherence by lipoteichoic acid and M-protein
• (LTA-M) complexes
Antigenic Structure
Streptococcus pyogenes (Group A)
Lancefield Group-specific antigen (C polysaccharide)
Complex polysaccharide in cell wall
Proteins: Two major classes, M & T antigens
Two minor classes, R & F
M-Protein: Type-specific antigen
Fimbriae-like, hairy extensions
Resistant to heat and acid
Trypsin Sensitive
Specific adherence by lipoteichoic acid and M-protein
(LTA-M) complexes
T Antigens (not virulence factor)
Resistant to trypsin, heat and acid;
Adjunct to M-typing; Routine surveillance
Others
Antigenic Structure (cont.)
Streptococcus pyogenes (Group A)
Capsular Polysaccharide:
Hyaluronic acid
Not present in all strains
Same as host hyaluronic acid (cartilage,skin etc)
Nonimmunogenic
Antiphagocytic
Hyaluronidase (cell wall division) during late growth
Lipoteichoic Acid
Lancefield Serogroup Classification of
Beta-Hemolytic Streptococci Important in
Human Disease
Group A Streptococci:
Streptococcus pyogenes
• One of Most Important Human Pathogens
• Suppurative Diseases:
Pharyngitis; Scarlet Fever;
Cutaneous & Soft Tissue Infections
Systemic Disease
• Non-Suppurative Sequelae:ARF,RHD,AG
Streptococcus
pyogenes
(Phase Contrast)
Lancefield Serogroup Classification of
Beta-Hemolytic Streptococci Important in
Human Disease (cont.)
Group B Streptococci:
Streptococcus agalactiae
•Neonatal disease & obstetric complications
•Systemic, Cutaneous, UTI's
Streptococcus
agalactiae
Lancefield Classification of BetaHemolytic Streptococci (cont.)
Group C Streptococci: Pharyngitis
Enterococcus & Group D Streptococci
Genitourinary Tract Infections (UTIs)
Endocarditis
Group G Streptococci:
S.anginosus-milleri grp; Streptococcus spp.
Pharyngitis
Non-Lancefield Group Streptococci
Viridans Streptococci
Dental Caries: Streptococcus mutans
Streptococcus sanguis; Streptococcus salivarius;
Streptococcus mitis
Streptococcus pneumoniae
Major Human Diseases of
Beta-Hemolytic Streptococci
Group A Streptococcus (S. pyogenes):
Diverse group of acute suppurative (pus-forming) &
nonsuppurative diseases
Suppurative Streptococcal Diseases
Pharyngitis (& tonsilitis):
Scarlet fever: Complication of streptococcal pharyngitis
when infecting strain is lysogenized; Frequently develop
scarletina rash on upper chest spreading to extremities
Cutaneous & Soft Tissue Infxns.
Pyoderma (Impetigo: contagious pyoderma with
superficial yellow weeping lesions)
Erysipelas: Acute superficial cellulitis of skin with
lymphatic involvement; face and lower extremities, skin
and subcutaneous tissues
Erysipelas
NOTE:
 erythema
 bullae
Major Human Diseases of
Beta-Hemolytic Streptococci (cont.)
Group A Streptococcus (S. pyogenes)
Suppurative Streptococcal Diseases
Cutaneous & Soft Tissue Infxns(cont.)
Cellulitis: Involvement of deeper subcutaneous
tissues; Deeper invasion with systemic symptoms
Necrotizing fasciitis: (a.k.a., “flesh-eating
bacteria”): Infection deep in subcutaneous tissues that
spreads along fascial planes, destroying muscle and fat;
Initially cellulitis followed by bullae (fluid filled blisters;
bulla is singular), gangrene, systemic toxicity, multiorgan
failure and mortality in more than 50% of patients
Wound Infections
Suppurative Streptococcal Diseases
Group A Streptococcus (cont.)
Other Suppurative Diseases
Puerperal & neonatal sepsis
Lymphangitis: Inflammation of lymphatic vessel(s)
Pneumonia
Systemic Disease
Streptococcal Toxic Shock
Syndrome (TSS): Multisystem toxicity following
soft tissue infection progressing to shock and organ
failure (not to be confused with Staphylococcal
Toxic Shock Syndrome where hyperabsorbent
tampons have been identified as an important risk
factor)
Bacteremia
Group A Streptococcal Diseases (cont.)
Nonsuppurative Sequelae
Post-infection complications of Group A streptococcal
disease; Serious complications in pre-antibiotic era;
still important in developing countries
Acute rheumatic fever (ARF):
Inflammation of heart, joints, blood vessels, subcutaneous tissues
Rheumatic heart disease (RHD):
Chronic, progressive heart valve damage
Acute glomerulonephritis (AG):
Acute inflammation of renal (kidney) glomeruli
Foodborne Disease
Epidemiology of Acute Streptococcal Infection
• Predilection for upper respiratory tract or skin
•Group A commonly colonize oropharynx of healthy children
• M-types of strains colonizing throat differ from those on skin
• Rapidly killed after phagocytosis, but cell walls not digested
and may lead to chronic inflammatory lesions
Pharyngitis transmitted by droplets from respiratory secretions
• Crowding increases risk (e.g., classrooms, day care facilities)
Pyoderma transmitted by direct contact with infectious lesions
Nonsuppurative Sequelae of Acute
Group A Streptococcal Infection
Acute Rheumatic Fever (ARF)
Inflammatory reaction characterized by arthritis, carditis, chorea
(disorder of CNS with involuntary spastic movements), erythema
marginatum (skin redness with defined margin), or subcutaneous
nodules
Within 2-3 weeks following pharyngitis
• Epidemic pharyngitis: ARF in as many as 3%
• Sporadic pharyngitis: ARF in 1 per 1000
Morbidity & mortality linked to subsequent disease of heart valve
(Rheumatic Heart Disease)
Poorly understood pathogenesis with several proposed theories
including cross-reactivity of heart tissues & strep AGNs
•?? (Type ??
II hypersensitivity, exotoxins, direct invasion)
Nonsuppurative Sequelae of Acute
Group A Streptococcal Infection (cont.)
Acute Glomerulonephritis
Follows either respiratory (pharyngitis) or cutaneous
(pyoderma) streptococcal infection
Associated with well-defined group of M-types
Incidence varies from <1% to 10-15%
Most often seen in children manifesting as dark, smoky
urine with RBC's, RBC casts, white blood cells, depressed
serum complement, decreased glomerular filtration rate
Latent period: 1-2 weeks after skin infection and 2-3 weeks
after pharyngitis
Granular accumulations of immunoglobulin due to
deposition of immune complexes within the kidney
III Hypersensitivity)
(Type ??
Determinants of Pathogenicity
Cellular Virulence Factors
Capsule
Antiphagocytic; Nonspecific adherence
Hyaluronic acid (polysaccharide) mimics animal tissue
Lipoteichoic Acid
Cytotoxic for wide variety of cells
Adherence: Complexes with M protein (LTA-M) and binds
to fibronectin on epithelial cells
M-Protein
LTA-M protein is adhesin
Antiphagocytic
Inhibits alternate C’ pathway and opsonization
M-like Proteins: bind IgM and IgG
F Protein: mediates adherence
Extracellular Virulence Factors
Exotoxins:
Streptolysin O (SLO):
Hemolytic and Cytolytic
Prototype of oxygen-labile and thiol-activated
cytolytic exotoxins (e.g., Streptococcus, Bacillus,
Clostridium, Listeria)
Lytic for variety of cells: bind to cholesterolcontaining membranes and form arc- or ring- shaped
oligomers that make cell leaky (RBC's, WBC’s, PMN's,
platelets, etc.)
Causes sub-surface hemolysis on BAP
Stimulate release of lysosomal enzymes
SLO titer indicates recent infection (300-500 in
pediatric populations)
Extracellellular Virulence Factors (cont.)
Exotoxins (cont.):
Streptolysin S (SLS):
Hemolytic and Cytolytic
Oxygen stable, non-antigenic
Lytic for red and white blood cells and wall-less forms
(protoplast, L- forms)
Causes surface hemolysis on BAP
Lysogeny: Lysogenized bacteriophages play key role
in directing synthesis of various Group A streptococcal
enzymes and toxins
• Pyrogenic Exotoxin (erythrogenic toxin)
• Phage-associated muralysins (lyse cell walls)
produced by both Groups A and C
Extracellular Virulence Factors (cont.)
Exotoxins (cont):
Pyrogenic (Erythrogenic) Exotoxins (Types A, B &C)
Produced by more than 90% of Grp A strep
Lysogeny: Structural gene is carried by temperate
bacteriophage, as is the case with diphtheria toxin
Mediate pyrogenicity (fever)
Causes scarlet fever (scarletiniform) rash
Increase susceptibility to endotoxic shock
Type C toxin increases permeability of blood-brain barrier
Enhance DTH
Mitogenic for T lymphocytes (cause cell division), myocardial
and hepatic necrosis, decrease in antibody synthesis
Immunomodulators (superantigens): stimulate T cells to
release cytokines
Cardiohepatic toxin
Extracellular Virulence Factors (cont.)
Enzymes:
Nucleases: Four antigenic types (A,B,C,D)
Facilitate liquefication of pus generating growth substrates
Nucleases A, C have DNase activity
Nucleases B, D also have RNase activity
Streptokinases: Two different forms
Lyse blood clots: catalyze conversion of plasminogen to
plasmin, leading to digestion of fibrin
C5a Peptidase: destroys C’ chemotactic signals (C5a)
Hyaluronidase: hydrolyzes hyaluronic acid
Others: Proteinase, NADase, ATPase, phosphatase, etc.
Lab Identification of
S. pyogenes (Group A)
• Primary culture by pour or streak plate
• Domed,grayish/opalescent colonies
• Encapsulated cells produce mucoid colonies
Beta-hemolytic
• Zone several times greater than diameter of colony
TSA
S. pyogenes
Lab Identification of
S. pyogenes (Group A) (cont.)
Catalase Negative: Differentiates from Staphylococcus
Bacitracin test: presumptively distinguishing between Group
A beta-hemolytic streptococci (bacitracin POS) and other betahemolytic streptococci that are isolated from pharyngeal
swabs (95% sensitivity for Grp A strep)
Rapid Identification Tests:
Based on extraction of Group A carbohydrate directly from
throat swabs
• ELISA, Coagglutination, Fluorescent Antibody
Group B Streptococcus
Streptococcus agalactiae
Group B Streptococcal Infections
Grp B Streptococcal Infections (cont.)
Age-Specific Attack Rates of Group B
Streptococcal Disease
Epidemiology of Neonatal Group B
Streptococcal Disease
Group B Streptococcus
S. agalactiae
Diagnostic Laboratory Tests
• CAMP factor positive
• Hippurase positive
CAMP Factor Test
Group B
Streptococcus
S. aureus
(Spingomyelinase C)
(CAMP Factor)
Group A
Streptococcus
Enhanced
Zone of
Hemolysis
Hippurase NEG
Grp B Streptococci
and
Campylobacter
Hippurase POS
Streptococcus pneumoniae
• Commonly referred to as pneumococcus
• Formerly Diplococcus pneumoniae
Streptococcus pneumoniae Infections
Pneumococcal Infections (cont.)
Epidemiology (cont.)
S. pneumoniae
• Diplococcus
S. pneumoniae: lancet-shaped diplococcus
S. pneumoniae Virulence Factors
S. pneumoniae Seasonal Incidence
Comparison
of Morbidity
& Mortality
for Bacterial
Meningitis
Genetic Variation (Mutation)
Beginning of Molecular Genetics
Transformation (In vivo) (Griffith)
Streptococcus pneumoniae
Diagnostic Laboratory Tests
• Optochin sensitivity (Taxo P disc)
Optochin Sensitivity
Taxo P
Streptococcus
pneumoniae
Enterococcus faecalis
Enterococcus faecium
• GI tract of humans and animals
• Group D carbohydrate cell wall antigen
• Formerly Streptococcus
Enterococcal Infections
Enterococcal Infections (cont.)
 Important nosocomial pathogen
 Vancomycin resistant Enterococcus (VRE)
Enterococcus
Diagnostic Laboratory Tests
• Resistant to bile
• Esculin hydrolysis
• BEA media
Enterococcus
Group D Streptococcus
Bile Esculin Agar
Bile Esculin Agar
NEG
POS
Esculin
Bile
Assay
REVIEW
Lancefield Serogroup Classification of
Beta-Hemolytic Streptococci Important in
Human Disease
Group A Streptococci:
Streptococcus pyogenes
One of Most Important Human Pathogens
Suppurative Diseases: Pharyngitis; Scarlet Fever;
Cutaneous & Soft Tissue Infections; Systemic
Disease
Non-Suppurative Sequelae:ARF,RHD,AG
Group B Streptococci:
Streptococcus agalactiae
Systemic, Cutaneous, UTI's
Neonatal disease
Obstetric Complications
REVIEW
Nonsuppurative Sequelae of Acute
Group A Streptococcal Infection
Acute Rheumatic Fever (ARF)
Inflammatory reaction characterized by arthritis, carditis, chorea
(disorder of CNS with involuntary spastic movements), erythema
marginatum (skin redness with defined margin), or subcutaneous
nodules
Within 2-3 weeks following pharyngitis
• Epidemic pharyngitis: ARF in as many as 3%
• Sporadic pharyngitis: ARF in 1 per 1000
Morbidity & mortality linked to subsequent disease of heart valve
(Rheumatic Heart Disease)
Poorly understood pathogenesis with several proposed theories
including cross-reactivity of heart tissues & strep AGNs
•?? (Type ??
II hypersensitivity, exotoxins, direct invasion)
REVIEW
Nonsuppurative Sequelae of Acute
Group A Streptococcal Infection (cont.)
Acute Glomerulonephritis
Follows either respiratory (pharyngitis) or cutaneous
(pyoderma) streptococcal infection
Associated with well-defined group of M-types
Incidence varies from <1% to 10-15%
Most often seen in children manifesting as dark, smoky
urine with RBC's, RBC casts, white blood cells, depressed
serum complement, decreased glomerular filtration rate
Latent period: 1-2 weeks after skin infection and 2-3 weeks
after pharyngitis
Granular accumulations of immunoglobulin due to
deposition of immune complexes within the kidney
III Hypersensitivity)
(Type ??
REVIEW
Determinants of Pathogenicity
Cellular Virulence Factors
Capsule
Antiphagocytic; Nonspecific adherence
Hyaluronic acid (polysaccharide) mimics animal tissue
Lipoteichoic Acid
Cytotoxic for wide variety of cells
Adherence: Complexes with M protein (LTA-M) and binds
to fibronectin on epithelial cells
M-Protein
LTA-M protein is adhesin
Antiphagocytic
Inhibits alternate C’ pathway and opsonization
M-like Proteins: bind IgM and IgG
F Protein: mediates adherence
REVIEW
Extracellular Virulence Factors
Exotoxins:
Streptolysin O (SLO):
Hemolytic and Cytolytic
Prototype of oxygen-labile and thiol-activated
cytolytic exotoxins (e.g., Streptococcus, Bacillus,
Clostridium, Listeria)
Lytic for variety of cells: bind to cholesterolcontaining membranes and form arc- or ring- shaped
oligomers that make cell leaky (RBC's, WBC’s, PMN's,
platelets, etc.)
Causes sub-surface hemolysis on BAP
Stimulate release of lysosomal enzymes
SLO titer indicates recent infection (300-500 in
pediatric populations)
REVIEW
Extracellellular Virulence Factors (cont.)
Exotoxins (cont.):
Streptolysin S (SLS):
Hemolytic and Cytolytic
Oxygen stable, non-antigenic
Lytic for red and white blood cells and wall-less forms
(protoplast, L- forms)
Causes surface hemolysis on BAP
REVIEW
Extracellular Virulence Factors (cont.)
Exotoxins (cont):
Pyrogenic (Erythrogenic) Exotoxins (Types A, B &C)
Produced by more than 90% of Grp A strep
Lysogeny: Structural gene is carried by temperate
bacteriophage, as is the case with diphtheria toxin
Mediate pyrogenicity (fever)
Causes scarlet fever (scarletiniform) rash
Increase susceptibility to endotoxic shock
Type C toxin increases permeability of blood-brain barrier
Enhance DTH
Mitogenic for T lymphocytes (cause cell division), myocardial
and hepatic necrosis, decrease in antibody synthesis
Immunomodulators (superantigens): stimulate T cells to
release cytokines
Cardiohepatic toxin
REVIEW
Extracellular Virulence Factors (cont.)
Enzymes:
Nucleases: Four antigenic types (A,B,C,D)
Facilitate liquefication of pus generating growth substrates
Nucleases A, C have DNase activity
Nucleases B, D also have RNase activity
Streptokinases: Two different forms
Lyse blood clots: catalyze conversion of plasminogen to
plasmin, leading to digestion of fibrin
C5a Peptidase: destroys C’ chemotactic signals (C5a)
Hyaluronidase: hydrolyzes hyaluronic acid
Others: Proteinase, NADase, ATPase, phosphatase, etc.
REVIEW
Epidemiology of Neonatal Group B
Streptococcal Disease
REVIEW
REVIEW
Streptococcus pneumoniae Infections
Infections from endogenous spread from naso- or orapharynx
Pneumonia; sinusitis; otitis media; bacteremia; meningitis
Colonization highest in children
Antecedent viral respiratory tract disease increases risk
Most common in cold months
Polyvalent vaccine available (newly available for children)
REVIEW
S.pneumoniae Virulence Factors
REVIEW
Comparison
of Morbidity
& Mortality
for Bacterial
Meningitis
REVIEW
Genetic Variation (Mutation)
REVIEW
Beginning of Molecular Genetics
REVIEW
Transformation (In vivo) (Griffith)
REVIEW
Enterococcal Infections
Group D cell wall antigen
Enterococcus faecalis; Enterococcus faecium
GI tract of humans and animals
UTI most common; wound infections; bacteremia; endocarditis
Most infections from endogenous source
Prolonged hospitalization and broad-spectrum antibiotics
increase risk
Antibiotic resistance (VRE)
REVIEW