Streptococcus, Enterococcus, Pneumococcus, and Staphylococcus

GRAM POSITIVE COCCI

Eric Stanbridge, PhD

Important Terms

Pyogenic = Pus-inducing

Pyrogenic = Fever-inducing

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

α-hemolysis

β-hemolysis

γ-hemolysis (non-hemolytic)

Streptococcal Serogroups

Based upon the polysaccharide layer external to the peptidoglycan.

(E. faecium)

Group A Streptococcus

One species:

Streptococcus pyogenes

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)

Streptococcal pharyngitis

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)

Streptococcal Impetigo

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)

Cellulitis

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)

Scarlet Fever

Toxic Shock-Like Syndrome (TSLS)

S.pyogenes growingin an infected wound→Bacteremia Production of SpeA ↓ Fever, Rash, Shock

Streptococcus pyogenes

Non-suppurative SEQUELAE:

•Acute Rheumatic Fever•Acute Glomerular Nephritis

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)

Diplococci

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)

Normal lung

Lobar pneumonia

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)

Staphylococci

S.aureus

S.epidermidis

S. saprophyticus

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

Staphimpetigo

“ScaldedSkin”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