Streptococcus agalactiae, Groups C and G Streptococci, Streptococcus anginosus group, Groups E, F, G, H and K-U Streptococci, Viridans streptococci.

Question 1

Streptococcus agalactiae

Answer 1

Group B streptococcus (GBS) is a gram-positive coccus, beta-hemolytic, catalase-negative, and often found in chains. It is part of normal flora of the female genital tract and rectum. Major virulence factor is the polysaccharide capsule that inhibits phagocytosis. It is a leading cause of neonatal sepsis, meningitis, and pneumonia, acquired during birth. In adults, it causes postpartum endometritis, UTIs, and soft tissue infections. Lab tests: CAMP test positive (enhances S. aureus hemolysis), hippurate hydrolysis positive, bacitracin-resistant. Treated with penicillin; pregnant women are screened at 35–37 weeks and given intrapartum prophylaxis if positive.

Question 2

Groups C and G streptococci

Answer 2

Groups C and G streptococci are beta-hemolytic and resemble S. pyogenes but are less virulent. They are part of the normal flora of human throat, skin, and GI tract. They can cause pharyngitis, cellulitis, bacteremia, endocarditis, and abscesses. Species include Streptococcus dysgalactiae subspecies equisimilis. They are bacitracin-resistant and lack M protein. Treatment is with penicillin or cephalosporins.

Question 3

Streptococcus anginosus group

Answer 3

Also called S. milleri group, includes S. anginosus, S. intermedius, and S. constellatus. These bacteria may be alpha-, beta-, or non-hemolytic. They are part of the normal flora of the oral cavity, GI tract, and vagina. Notable for their ability to form abscesses in brain, liver, or peritoneum. Often identified by a characteristic butterscotch odor. Lancefield groups A, C, F, and G may be expressed. Treated with penicillin and drainage of abscess if needed.

Question 4

Groups E, F, G, H and K–U streptococci

Answer 4

These streptococci are less commonly encountered and often part of normal flora. They are beta-hemolytic and classified by Lancefield grouping based on carbohydrate antigens. Some may cause human infections like pharyngitis, cellulitis, or wound infections, but their pathogenic role is often unclear. Group F is usually part of the S. anginosus group and associated with deep-seated abscesses. Groups E, H, and K–U are rare in clinical practice. Identification is done using serologic grouping and culture.

Question 5

Viridans streptococci

Answer 5

A heterogeneous group of alpha-hemolytic streptococci (e.g., S. mutans, S. mitis, S. sanguinis, S. salivarius). They are part of normal oral flora and are a major cause of dental caries (S. mutans). They cause subacute bacterial endocarditis, especially in patients with damaged heart valves. Also implicated in brain or liver abscesses and bacteremia in neutropenic patients. They are optochin-resistant, bile insoluble, and not classified by Lancefield groups. Treated with penicillin, sometimes combined with gentamicin for endocarditis.