Genus Streptococcus


All Streptococcus spp. (streptococci) possess the following characteristics
  • GPC (Gram-positive cocci) that are spherical or ovoid in shape, 2 m in diameter, and usually arranged in chains  and pairs
  • Facultative anaerobes
  • Nonmotile
  •  Do not form spores
  • Catalase negative (i.e., they do not produce the enzyme catalase)
Beta-hemolytic Streptococci (Lancefield Groups)
Beta-hemolytic Streptococci
  • Group A Streptococi (Strept. Pyogenes)
  • Group B Streptococi (Strept. agalactiae)
  • Group C Streptococci Group
  • G Streptococci


S. pyogenes


S. pyogenes is a very important human pathogen. It is the major cause of strep throat. Scarlet fever is  also caused
by S. pyogenes strains that produce erythrogenic toxin. Some strains  of this microorganism are the infamous flesh-eating bacteria. They produce necrotizing enzymes that cause rapid and extensive destruction of tissue—a condition which is known as necrotizing fasciitis.

The toxic shock disease caused by S. pyogenes is technically called toxic shock–like syndrome (TSLS) and is caused by a toxin that is somewhat similar to the TSST-1 produced by S. aureus. However, the TSLS toxin is different. It is
called streptoccocal pyrogenic toxin (Spe).

S. pyogenes has not developed resistance to penicillin, so penicillin remains the drug of choice to treat
strep throat and most other S. pyogenes infections. Some strains of this microorganism developed resistance to erythromycin and many strains are resistant to tetracycline.

Alpha-hemolytic Streptococci
Alpha-hemolytic Streptococci
  • Streptococcus Pneumoniae (Pneumococcus)
  • Streptococcus Viridans(Bacterial Endocarditis)
Non-hemolytic Streptococci
Non-hemolytic Streptococci
Strept. faecalis (Group D)
Other Species
Certain members of Groups B, C, D, H, and O
Specific treatment
Medications that are specific for Streptococcus:

The following medications are specific for Streptococci:

  • Penicillin
  • Ampicillin
  • Amoxicillin
Other ( nonspecific) medications
Nonspecific treatment options

IV: Oxacillin/nafcillin, or cefazolin (first-generation cephalosporin)
Oral: Dicloxacillin or cephalexin (first-generation cephalosporin)
Severe infection: Vancomycin, linezolid, daptomycin, ceftaroline, tigecycline, or telavancin.
Minor infection: Trimethoprim/sulfamethoxazole (TMP/SMX), clindamycin, doxycycline