Bacteriology-33 Streptococcal Bacterial Infections*

Front 1

What are the major diseases caused by Streptococci

Back 1

Bacteremia (all types)
Pneumonia (Streptococcus pneumoniae)
Otitis media (S. pneumoniae)
Meningitis (Streptococcus pneumoniae, group B streptococci)
Cellulitis (group A, less commonly group B)
Necrotizing fasciitis and myositis (group A)
Impetigo (group A)
Pharyngitis (Group A)
Scarlet fever (group A)
Toxic shock-like syndrome (group A)
rheumatic fever (group A)
Acute glomerulonephritis (group A)
Wound infections (group A streptococci, enterococci, anaerobic streptococci)
Endocarditis (Enterococcus species, Viridans streptococci)
UTIs (Enterococcus species)

Front 2

What are some characteristics of all streptococci

Back 2

Gram positive, spherical, grow in pairs or chains, non motile, catalase negative

Front 3

What is the most common cause of community-acquired pneumonia in the United States (500,000/year)

Back 3

Streptococcus pneumoniae

Front 4

What is one of the most common causes of acute suppurative otitis media in the US (7,000,000/year)

Back 4

Streptococcus pneumoniae. The bacteria also causes bacteremia and bacterial meningitis

Front 5

What is the morphology of Streptococcus pneumoniae

Back 5

Alpha hemolytic (but not true lysis)
Gram positive, lancet-shaped diplococci
Catalase negative
Grow best with 5-10% blood on media
Autolytic enzymes cause lysis of colony in bile salts (bile solubility) and susceptibility to optochin

Front 6

What are the three main virulence factors in Streptococcus pneumoniae

Back 6

Capsular polysaccharides; Adhesins; Pneumolysin

Front 7

What are the characteristics of capsular polysaccharides in Streptococcus pneumoniae

Back 7

Antigenic, ~90 serotypes
Antiphagocytic (main virulence factor). Prevents deposition of C3b

Front 8

What are the adhesins in Streptococcus pneumoniae

Back 8

Pneumococcal surface protein A (PspA) and choline-binding proteins. Thought to facilitate binding of pneumococci to pharyngeal cells

Front 9

How does Pneumolysin in Streptococcus pneumoniae work

Back 9

This is a membrane active, pore-forming toxin. The toxin may also destroy ciliated epithelial cells and block the phagocytic burst

Front 10

What are the predisposing factors to acquiring pneumonia from Streptococcus pneumoniae

Back 10

Viral infection of upper respiratory tract, particularly influenza
Compromised pulmonary function, alcoholism, general anesthesia
Age
Basic immunity is impaired
Serotype present (type 3 responsible for most disease)

Front 11

Where does an infection of Streptococcus pneumoniae usually come from

Back 11

Most are caused by endogenous infection

Front 12

What is the pathogenesis of pneumococcal pneumoniae

Back 12

Organism colonizes pharynx and gains access to the lungs
Moves to alveoli and is phagocytized by macrophages
Multiplies in edematous fluid
Exudate spills into bronchioles and adjoining alveoli
Inflammatory response, air is displaced

Front 13

What are the clinical manifestations of pneumococcal pneumonia

Back 13

Sudden onset of chills, fever, pleuritic pain, rusty sputum
Positive blood cultures in 30%

Front 14

What are some possible complications in pneumococcal pneumonia

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Direct-lung abscess
Via blood-Empyema, pericarditis, meningitis, intrapleural abscess, septic arthritis

Front 15

What is the morbidity and mortality of Streptococcus pneumoniae

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Causes pneumonia, otitis media, invasive diseases including meningitis. Death occurs in 14% with invasive disease. Factors that affect severity include age, bacteremia, and serotype

Front 16

What are some upper respiratory tract infections caused by Streptococcus pneumoniae

Back 16

Otitis media, Mastoiditis, Sinusitis

Front 17

What are some extrapulmonary infections caused by Streptococcus pneumoniae

Back 17

Meningitis- most common cause in US
Septic arthritis
Endocarditis

Front 18

How is Streptococcus pneumoniae identified on blood agar

Back 18

Colonies are mucoid, alpha hemolytic, bile soluble. The bacteria are also sensitive to optochin

Front 19

What are the different types of specimens that can be used to identify Streptococcus pneumoniae

Back 19

Blood, CSF, sputum, transtracheal aspirate. Concentrated urine can be used for detection of C polysaccharide (teichoic acid plus tightly adherent fragments of peptidoglycan), which is present in all pneumococci. This is not recommended for patients with pneumonia

Front 20

What can be used for rapid, presumptive identification of Streptococcus pneumoniae

Back 20

Gram stain appearance in CSF or sputum or detection of soluble capsule by latex agglutination. Can also use CIE (serum or CSF) or ELISA

Front 21

How is Streptococcus pneumoniae treated in:
Otitis media
Sinusitis
Pneumonia
Meningitis

Back 21

There has been an increase of pen G resistance and cephalosporins, due to altered PBPs.
Otitis media: amoxicillin
Sinusitis: amoxicillin or quinolone
Pneumonia: third generation cephalosporins
Meningitis: vancomycin plus Beta-lactam antibiotics

Front 22

How is immunity to Streptococcus pneumoniae acquired

Back 22

It is serotype specific. Recovery correlates with development of opsonizing antibody to polysaccharide capsule

Front 23

What are the two vaccines available for Streptococcus pneumoniae

Back 23

Prevenar-heptavalent pneumococcal conjugate vaccine (23 months or younger)
Polysaccharide only vaccine. All 23 serotypes, primarily protects against bacteremia

Front 24

What streptococci, other than pneumococci, are frequently associated with human disease

Back 24

Groups A, B (sometimes C, F and G) and Enterococcus (old group D)

Front 25

What is the most important Streptococcus group A species

Back 25

Streptococcus pyogenes

Front 26

What is the background of Streptococcus pyogenes

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Responsible for majority of all streptococcal diseases
Transient flora in upper respiratory tract of 15-20% of school-age children

Front 27

In a conventional culture, how is Streptococcus pyogenes identified

Back 27

Gram positive cocci
Beta-hemolytic pinpoint; convex colonies on blood agar; colonies may be mucoid
Catalase negative
PYR test positive
Bactitracin sensitive

Front 28

What are the two main laboratory identifications for Streptococcus pyogenes

Back 28

Direct antigen test (ELISA) or conventional culture

Front 29

What is the cellular structure of Streptococcus pyogenes

Back 29

Pili
Lipoteichoic acid- adherence to fibronectin
M protein- major virulence factor, antiphagocytic, 90 different types
F protein- mediates binding to fibronectin
Hyaluronic acid capsule- same as host surface
Group specific Lancefield CHO antigen

Front 30

What are the extracellular Streptococcus pyogenes products

Back 30

Streptococcal pyrogenic toxins- similar to Staphlococcal pyrogenic toxins. Super antigens, involved in scarlet fever and toxic shock-like syndrome
Streptolysin- O2 labile, antigenic, hemolytic, toxic to wide variety of cells
DNAases
Streptokinase plus streptodornase- enzymatic debridgement
C5a peptidase degrades C5a that attracts PMNs

Front 31

What Acute suppurative infections does Streptococcus pyogenes cause

Back 31

Impetigo- climate and hygiene affect incidence
Wound infections
Pharyngitis
Cellulitis
Necrotizing fasciitis and myositis- probably due to group A streptococci that make both pyrogenic exotoxin A and a cysteine protease
Streptococcal toxic shock syndrome. Clinically like Staphylococcal toxic shock syndrome except patients are bacteremic

Front 32

What are two non-suppurative sequelae of Streptococcus pyogenes

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Rheumatic fever and acute glomerulonephritis

Front 33

How is Streptococcus pyogenes treated

Back 33

Penicillin G. If in shock, add clindamycin. If coinfected with S. aureus, use penicillinase-resistant antibiotic

Front 34

What is the only Group B streptococci species

Back 34

Streptococcus agalactiae

Front 35

What is the background of Streptococcus agalactiae (Group B)

Back 35

First isolated from bovine mastitis
Most common cause of neonatal meningitis
Normal flora in the gut and transient flora in the vagina of pregnant women

Front 36

How are Streptococci agalactiae identified

Back 36

Gram positive cocci, catalase negative
Beta hemolytic and bacitracin insensitive
CAMP test positive CAMP factor
Detection of group B specific cell wall antigen

Front 37

What are the characteristics of neonatal infections with Streptococci agalactiae

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Early or Delayed onset. Vertical transmission. Can see meningitis, sepsis, 20% mortality

Front 38

What Streptococcus agalactiae infections are seen in adults

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Pregnant- bacteremia
Non pregnant- bacteremia, meningitis, cellulitis

Front 39

How is Streptococcus agalactiae treated

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Penicillin G plus aminoglycoside

Front 40

How are Streptococcus agalactiae infections prevented

Back 40

Working on a vaccine
Penicillin G during labor to women at risk

Front 41

What are the characteristics of Enterococci (group D) and Streptococcus bovis (group D or Viridans)

Back 41

Normal flora on skin and GI tract
Gram positive cocci, catalase negative
Alpha, beta, or gamma hemolytic
Bacitracin insensitive, hydrolyze bile-esculin
Enterococci grow in 6.5% NaCl
Cause infections in the urinary tract, bacteremia (most common type of streptococcal bacteremia in adults), and wound infections

Front 42

How are enterococci treated

Back 42

Penicillin G + aminoglycoside

Front 43

What are the characteristics of Viridans streptococci

Back 43

Were called alpha hemolytic streptococci
Normal flora of the mouth, URT. Not typable by CHO antigen, usually don't cause disease
Gram positive cocci, catalase negative, alpha hemolytic, optochin insensitive
Can cause Endocarditis after dental work, or dental cares. Treat with penicillin G