• General Classification

• Lancefield Group Classifications

• Group A Streptococci: Pharyngitis

• Group A streptococci: Impetigo

• Group A streptococci: Cellulitis

• Group A streptococci: Deep Soft Tissue Infection

• Group A streptococci: Pneumonia and Empyema

• Group C and G Streptococci

• Group B Streptococci

• Viridans

• Streptococcal classifications: Lansfield Groups A, B, C, D, G, Variable:

• Lancesfield classification is based on differing serologic reactions to specific antisera with cell-wall carbohydrate bacterial antigens.

• Each group is characterized by a particular pattern of human infection. Nearly all organisms belonging to groups A, B, C and G are beta-hemolytic streptococci.

Lancefield Group

Example

Hemolytic
Pattern

Infections

A

S. pyogenes

ß

pharyngitis, scarlet fever, impetigo, cellulitis

B

S. agalactiae

ß

Neonatal sepsis and meningitis, puerperal infection, urinatry tract infection (UTI), diabetic ulcer infection, endocarditis

C

S. equi

ß

Cellulitis, bacteremia, endocarditis

D

Enterococci: E. faecalis, E. faecium

usually non-hemolytic

UTI, wound infections, endocarditis

D

Nonenterococcal: s. bovis

usually non-hemolytic

Bacteremia, endocarditis

G

S. canis

ß

Cellulitis, bacteremia, endocarditis

Variable/Non-groupable

Viridans streptococci: S. mutans, S. sanguis

alpha

endocarditis, dental abscess, brain abscess

Variable/Non-groupable

Intermedius or milleri group: S. intermedius

variable

Brain abscess, visceral abscess

Variable/Non-groupable

Anaerobic streptococci: Peptostreptococcus magnus

usually non-hemolytic

Sinusitis, pneumonia, empyema, brain abscess, liver abscess

Table from: Wessels, M.R., Streptococcal and Enterococcal Infections, In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, p. 885.

• Group A streptococcal pharyngitis is one of the most common bacterial infections of childhood (20% to 40%) of cases, although rare under the age of three.

  • Following an incubation period of 1 - 4 days, symptoms commonly include sore throat, fever and chills and occasionally vomiting, especially in children.

  • Definitive diagnosis is by throat culture (gold standard) , but high specificity (95%) using rapid diagnostic kits (using latex agglutination or enzyme immunoassay of swab specimens) make these kits useful.

  • A positive result from these kits can allow definitivie diagnosis and eliminate the need for throat culture; however, a negative result should be confirmed with throat culture because the kits are relatively less sensitive (55% to 90%).

  • Follow-up culture may be warrented if there is concern for Rheumatic fever development (cases reported in the community)

• Drug Treatment: Benazthine Penicillin; penicillin V or erthyromycin in patients allergic to penicillin
   

• Impetigo: superficial skin infection is caused by Group A streptococci, although S. aureus may be present later in the course of infection.

• Drug Treatment: Dicloxacillin, cephalexin, topical mupirocin are most reliable; penicillin (benzathine penicillin/penicillin V) or erythromycin is less costly and equally effective.

• Cellulitis: Infection involving the skin and subcutaneous tissue.

  • Steptococcal cellulitis is most often localized to sites of normal lymphatic drainage.

  • Localized cellulitis may be accompanied by lymphangitis (red streaking along superificial lymphatics)

• Drug Treatment: Severe: penicillin G; mild to moderate: procaine penicillin

• Necrotizing fasciitis or hemolytic streptococcal gangrene involves superficial and/or deep fascia.

  • If cases are associated with bowel flora, the infection is usually due to Bacteriodes fragilis or anaerobic streptococci along with gram negative bacilli).

  • Cases not resulting from bowel contamination are ususally due to group A streptococci (60% of the time)

• Drug Treatment: Penicillin G (surgical debridement essential)

• Group A streptococci may cause pneumonia, occasionally, with pleural effusions occurring about 50% of the time.

  • Pleural effusions due to Group A streptococci are usually infected, by contrast to that seen with pneumococcal penumonia.

• Drug Treatment: Penicillin G

• Infections are similar to those caused by Group A.

  • These infections occur most often in the elderly and chronically ill.

• Drug Treatment of Choice: Penicillin, with the addition of gentamicin if patients respond poorly to penicillin alone for treatment of endocarditis or septic arthritis.

• Group B streptococci, S. agalactiae, is a significant cause of sepsis and meningitis in the newborn and peripartum fever in women.

• Neonatal risk factors for Group B strept. infections: preterm deliver, eary membrane rupture, prolonged labor, fever or chorioamnionitis.

• Emperical broad antibiotic coverage for suspected neonatal bacterial sepsis is ampicillin and gentamicin.

• Viridans streptococci consist of a variety of alpha-hemolytic streptococci, including S. salivarius, mutans, sanguis, and mitis, all common oral flora. Transient viridans endocarditis may be caused by eating, tooth-brushing, etc.

• Viridans bacteremia is frequently observed in neutropenic patients, especially after bone-marrow transplantation or high-dose cancer chemotherapy. Manifestation of infection may include high fever and shock (sepsis syndrome).

• Risk factors include: antibiotic prophylaxis with trimethoprim-sulfamethoxazole or a fluoroquinolone, mucositis, use of antacids or histamine antagonists, and significant neutropenia.

• In the neutropenic patients, vancomycin is the initial drug of choice before results of susceptibility testing are available, given that many viridans steptococci strains isolated from the neutropenic patient are penicillin resistant.

• Viridans streptococci strains isolated in other settings usually are sensitive to penicillin.