Bacterial diseases caused by Gram-positive cocci 

1. Staphylococcus
   • Irregular clusters; facultative anaerobes; coagulase-positive
   • Immune system avoidance mechanisms include 
     • capsule (slime layer)
     • protein A (binds Fc portion of IgG)
     • coagulase (clumping factor)
   • Multiple virulence factors, including cytotoxins, exfoliate toxins, enterotoxins, TSS toxin, hyaluronidase, coagulase, lipase, DNAse, adhesins, fibrinolysin, penicillinase, mecA gene (MRSA)
     • alpha toxin: creates membrane pores (blood vessels, smooth muscle, liver cells, blood cells)
     • beta toxin: sphingomyelinase (damages membranes)
     • delta toxin: membrane disruptor (detergent action)
     • gamma toxin: hemolytic & leukocidal (pore formation)
     • P-V leukocidin: leukotoxic (pore formation, not hemolytic); CA-MRSA
     • ETA & ETB: damage desmosomes in epidermis = cause exfoliation
     • Enterotoxins (A, B, C, D, E, G, H, I) (30 - 50% of Staph): superantigens, stimulate T-cells, mast cells
     • TSST-1: superantigen; heat resistant, causes endothelial leakage, cytotoxic effects, hypovolemic shock
   • PG: endotoxin-like activity (complement activation, IL-1 release, PMN aggregation (abscesses)
2. Streptococcus
   • Short or long chains of Gram-positive cocci
   • Clinically distinguished based on hemolysis pattern (alpha, beta, gamma) and serotypes (Group A - H, K etc.)
   • Anatomical syndromes include pharyngitis, bacteremia, and endocarditis
   • Streptococci can avoid immune system through capsule and M-proteins
   • Produce virulence factros: Adhesins, streptolysisn (causes hemolysis), streptokinase, DNAse
   • Pyrogenic exotoxins (Spe) stimulate release of cytokines, resulting in many disease symptoms
3. Enterococcus
   • Chains of Gram-positive cocci; bile-resistant
   • broad range of salt, pH, temperature tolerance; biofilm/adhesion
   • One of the leading causes of nosocomial infections
   • Increasing drug resistance (e.g. VRE)
   • Endocarditis is a leading cause of mortality
4. Rhodococcus
   • pneumonia-like (TB-like) infections in foals, immunocompromised humans
   • Plasmid-associated virulence factors
   • survives intracellularly in macrophage; tissue necrosis

Diseases caused by Gram-positive cocci

1. Bullous impetigo: Staphylococcus aureus
2. Carbuncles: Staphylococcus aureus
3. Endocarditis: Enterococcus, Staphylococcus, Streptococcus
4. Erysipelas: Streptococcus pyogenes
5. Food poisoning: Staphylococcus aureus
6. Folliculitis: Staphylococcus aureus
7. Furuncles: Staphylococcus aureus
8. Impetigo: Staphylococcus aureus, Group A Strep
9. Meningitis: Streptococcus pneumoniae
10. Necrotizing fasciitis: Streptococcus pyogenes
11. Pneumococcal pneumonia: Streptococcus penumoniae
12. Rheumatic fever: Streptococcus pyogenes
13. Scalded Skin Syndrome: Staphylococcus aureus
14. Scarlet fever: Streptococcus pyogenes
15. Strep throat: Streptococcus pyogenes
16. Toxic Shock Syndrome: Staphylococcus aureus, Streptococcus pyogenes