Staphylococcus and Streptococcus are the two most common pathogenic gram-positive cocci of medical importance. They share some important properties.
Common characteristics shared by these gram-positive cocci are:
- Nonmotile,
- Non-sporing,
- Facultative anaerobes
Some of the major differences between Staphylococcus and Streptococcus are summarized in the table below.
| Characteristic | Staphylococcus | Streptococcus |
| Shape | Gram-positive cocci in clusters (grape-like) because cell division occurs in various directions on multiple axes. Gram-positive cocci in pairs, tetrads, and short chains are also seen. | Streptococci are either Gram-positive cocci in pairs (S. pneumoniae) or short chains (S. pyogenes). This is because the cell division occurs on a single axis. |
| Catalase Test (Most Important test to differentiate Staph from Strep) | Staphylococci are catalase-positive (presence of catalase enzyme) | Streptococci are catalase negative |
| Growth Requirement | Staphylococci are not fastidious (does not need enriched media) | Streptococci are fastidious (need enriched media); so they cant grow in nutrient agar and need blood agar for growth. |
| Hemolysis | Staphylococci give no hemolysis or beta hemolysis. | Species of Streptococci are able to show any types of hemolysis (alpha or beta or gamma hemolysis). Hemolysis is a helpful tool to differentiate species of Streptococcus |
| Common habitat | Staphylococci are commensal of skin and anterior nares | Streptococci are found mainly in the mouth and respiratory tract as a commensal |
| Common diseases | Staphylococci mostly cause wound infections. Other diseases caused by this organism are osteomyelitis, acute endocarditis, septic arthritis, surgical site infection, interstitial pneumonia, etc. | Pathogenic species of streptococci cause pneumonia, meningitis, sore throat, wound infection, necrotizing fasciitis, scarlet fever, rheumatic fever, acute post-streptococcal glomerulonephritis |
| Most pathogenic species | Staphylococcus aureus Staphyloccus saprophyticus (in females for causing UTI) | Streptoccus pneumoniae Streptoccus pyogenes Streptococcus agalactiae |
| Useful diagnostic tests | Catalase test Coagulase test Novobiocin sensitivity test | Catalase test Bacitracin sensitivity test (S. pyogenes) Optochin sensitivity test (S. pneumoniae) Bile solubility test (S. pneumoniae) CAMP test (S. agalactiae) |
