Post on 23-Jul-2018
Streptococcus, Enterococcus, Pneumococcus, and Staphylococcus
GRAM POSITIVE COCCI
Eric Stanbridge, PhD
Important Streptococcal Pathogens•Streptococcus pyogenes (Group A)
•Streptococcus agalactiae (Group B)
•Enterococcus faecalis and E. faecium (Group D)
•Viridans Group (e.g. S. mitis, S. mutans, etc)
•Streptococcus pneumoniae
Streptococci Classification based on Hemolysis
S. pneumoniae
Group DViridans
Group A(S. pyogenes)
Group B(S agalactiae)
Viridans group Group D
γ (non-hemol.)βα
Hemolysis α
Serogrouping
Serotyping
β
Group A( S. pyogenes)
M protein ( > 80 serotypes)
λ (non)
Group A Streptococcus
Streptococcus pyogenes VIRULENCE FACTORS
♦Two Hemolysins: SLO and SLS
♦Erythrogenic Toxins: 3 SPE toxins phage encoded pyrogenic (fever-inducing) scarlet fever rash (rare) superantigen→cytokine release→ (TSLS) ♦ Exotoxin B→protease→destroys normal tissue (necrotizing fasciitis) ♦Streptokinase: plasminogen→plasmin (lysesblood clots) ♦Hyaluronidase: breaks down hyaluronic acid ♦DNAase and RNAase
Streptococcus pyogenes Acute Suppurative Diseases1. Pharyngitis2. Impetigo (superficial skin infection)3. Cellulitis (purulent inflammation of subcutaneous tissues)3a. Necrotizing Fasciitis4. Erysipelas5. Puerperal sepsis (uterine infection)6. Surgical wound infections7. Otitis media8. Scarlet Fever (rare)9. Toxic shock-like syndrome (TSLS)
Streptococcus pyogenes Acute Suppurative Diseases1. Pharyngitis2. Impetigo (superficial skin infection)3. Cellulitis (purulent inflammation of subcutaneous tissues)4. Erysipelas5. Puerperal sepsis (uterine infection)6. Surgical wound infections7. Otitis media8. Scarlet Fever (rare)9. Toxic shock-like syndrome (TSLS)
Streptococcus pyogenes Acute Suppurative Diseases1. Pharyngitis2. Impetigo (superficial skin infection)3. Cellulitis (purulent inflammation of subcutaneous tissues)4. Erysipelas5. Puerperal sepsis (uterine infection)6. Surgical wound infections7. Otitis media8. Scarlet Fever (rare)9. Toxic shock-like syndrome (TSLS)
Streptococcus pyogenes Acute Suppurative Diseases1. Pharyngitis2. Impetigo (superficial skin infection)3. Cellulitis (purulent inflammation of subcutaneous tissues)4. Erysipelas5. Puerperal sepsis (uterine infection)6. Surgical wound infections7. Otitis media8. Scarlet Fever (rare)9. Toxic shock-like syndrome (TSLS)
Skin and soft tissue infections
Epidermis
Dermis
Superficial fascia
Subcutaneous fat,nerves, arteries, veins
Deep fascia
Muscle
SkinSkin
SubcutaneousSubcutaneoustissuetissue
Necrotizingfasciitis
Myonecrosis
FolliculitisFurunclesCarbunclesImpetigo Erysipelas Ecthyma
Cellulitis
ANATOMY INFECTION
Green, R. J. et al. 1996. Necrotizing Fasciitis. Chest 110:219-229
MuscleMuscle
Streptococcus pyogenes Acute Suppurative Diseases1. Pharyngitis2. Impetigo (superficial skin infection)3. Cellulitis (purulent inflammation of subcutaneous tissues)4. Erysipelas (superficial form of cellulitis)5. Puerperal sepsis (uterine infection)6. Surgical wound infections7. Otitis media8. Scarlet Fever (rare)9. Toxic shock-like syndrome (TSLS)
Streptococcus pyogenes Acute Suppurative Diseases1. Pharyngitis2. Impetigo (superficial skin infection)3. Cellulitis (purulent inflammation of subcutaneous tissues)4. Erysipelas5. Puerperal sepsis (uterine infection)6. Surgical wound infections7. Otitis media8. Scarlet Fever (rare)9. Toxic shock-like syndrome (TSLS)
Toxic Shock-Like Syndrome (TSLS)
S.pyogenes growingin an infected wound→Bacteremia Production of SpeA ↓ Fever, Rash, Shock
S. pyogenes Sequelae Requirements 1. Acute Rheumatic Fever: •Preexisting infection of the upper respiratory tract •Persistence of the infection •Immune response to streptococcal antigens cross reacting with host tissues
Pathology: Autoimmunity (polyarthritis, carditis, chorea)
2. Acute Glomerular Nephritis:Complication of infection of upper respiratory tract OR skin
Pathology: Immune complex-mediated disease
S. pyogenes Lab ID
• β- hemolytic
• Catalase and coagulase negative (cf Staph aureus)
• Bacitracin sensitive (cf other β-hemolytic Strep)
Treatment♦ Penicillin G
♦Group B Streptococci (S.agalactiae)Meningitis and pneumonia in neonates
♦Group D StreptococciEnterococcus species ( E.faecalis, E.faecium)S.equinus, S.bovisIntraabdominal abscesses, urinary tract infections, bacteremia, endocarditis
♦Viridans GroupS. salivarius, S.mitis, S. sanguis, S. mutansDental CariesSubacute Bacterial Endocarditis
Microbiology of Infective Endocarditis
OrganismNative valveendocarditis
Intravenous drug abuse
Prosthetic valve endocarditisOnset in first yearfollowing surgery
Onset more than a yearfollowing surgery
Streptococci a-hemolytic, non hemolytic
S. bovis Other
Enterococci
Staphylococci S. aureus Coagulase-negative
Gram-negative aerobic rods
Fastidious Gram-negative rods
Fungi
Miscellaneous
Polymicrobial
Culture-negative
<5
5
30
10
>5
10
30
5
<5
<5
<1
5
8
<5
<1
8
55<5
8
<1
5
<5
5
8
5
<5
<1
<5
1055
5
<1
5
10
<5
10
30
<5
<1
10
1515
<5
8
<1
<5
<1
Treatment
S. agalactiae: Penicillin G
Viridans Group: Penicillin G (prolongedfor endocarditis)
Enterococcus: Multiple drug resistant, includingVancomycin
Group D (e.g. S. bovis): Penicillin G
Streptococcus pneumoniae
• α-hemolytic• Diplococcus• Carbohydrate capsule (virulence factor)• Bile soluble• Optochin sensitive (cf. viridansgroup)
Streptococcus pneumoniae PATHOGENESIS1. Pneumococcal pneumonia • Accounts for majority of bacterial pneumonias • Opportunistic pathogen • Sudden onset- fever, productive cough, lobar consolidation • Mortality due to complications associated with septic shock
2. Meningitis (most common cause of bacterial meningitis in ADULTS)3. Otitis media4. Endocarditis (acute, fulminating)
Streptococcus pneumoniae PATHOGENESIS1. Pneumococcal pneumonia • Accounts for majority of bacterial pneumonias • Opportunistic pathogen • Sudden onset- fever, productive cough, lobar consolidation • Mortality due to complications associated with septic shock
2. Meningitis (most common cause of bacterial meningitis in ADULTS)3. Otitis media4. Endocarditis (acute, fulminating)
S. aureus VIRULENCE FACTORS
1. Protein A (inhibits opsonization)2. Five cytolytic toxins (α-δ plus leukocidin)3. Six enterotoxins ( major cause of food poisoning)4. Exfoliatin toxin (causes desquamation, impetigo, scalded skin syndrome)5. TSST-1 (toxic shock syndrome toxin)
Plus various exoenzymes, including coagulase, lipase and hyaluronidase (role in virulence unclear)
S. aureus PATHOGENICITY1. Skin infections: folliculitis impetigo/ scalded skin syndrome boils, carbuncles2. Metastatic Abscesses: staph pneumonia osteomyelitis pyoarthritis
3. Enterocolitis4. Food poisoning5. Toxic shock syndrome
Toxic Shock Syndrome (TSS) versus TSLSS.pyogenes: growingin an infected wound→Bacteremia Production of SpeA ↓ Fever, Rash, ShockS.aureus: localizedinfection (tampon/ → TSST-1 toxin enters wound) bloodstream (no bacteremia) ↓ Fever, rash, shock
Treatment
Major problem of antibiotic resistance
>90% of S.aureus isolates are Pen G resistant
Approx 20% are methicillin resistant (MRSA)
Increasing problem of vancomycin resistance