There are a lot of similarities between Streptococcus (Strep) and Staphylococcus (Staph) that lead to confusion. Both are:
- spherical, facultatively anaerobic gram-positive bacteria
- common members of the normal human microbiota
- capable of resisting many forms of important antibiotics
- some species are capable of being pathogenic, responsible for serious infections and even deaths directly or indirectly through virulence factors such as toxins
The key differentiating characteristics between these two groups of bacteria are:
- their formation and cell division e.g. division occurs on a single axis growing in pairs or chains (Strep) vs division in various directions on multiple axes (Staph) growing in grape-like clusters
- their ability to produce catalase (enzyme to break down hydrogen peroxide) e.g. Strep is catalase negative vs Staph is catalase positive
- their need for enriched media for growth (e.g. Strep needs enriched media (fastidious) vs Staph does not need enriched media (not fastidious))
- most staphylococci are found on the skin whereas most streptococci are found in the respiratory tract.
When Streptococcus is seen dividing through a microscope, it is shaped spherically, remaining attached and growing in beadlike pairs or chains. Many species of Streptococcus are common and do not cause any human disease. This bacterium is commonly found in the throat but doesn’t always show any symptoms that indicate a disease. Some species under certain conditions, can cause infections.
The type of infections you can get from Streptococcus pyogenes are rheumatic fever (inflammatory disease that effects the heart, joints, skin and brain), impetigo (skin infection), scarlet fever, puerperal fever, streptococcal toxic shock syndrome, strep throat, tonsillitis, and other upper respiratory infections. Some symptoms of Streptococcus include: fever, sore throat and swollen lymph nodes, red & weeping skin sores, rash, dizziness and confusion.
Under a microscope, Staphylococcus looks like a bunch of grapes or little round berries often found in clusters or pairs (image above). These bacteria are most often found on the skin or in the mucus membranes of healthy people and can remain there without signs of infection. Under certain circumstances, such as wounds, cuts, or in-dwelling catheters, Staphylococcus can become pathogenic. The types of infections one can get from this type of bacteria are bacteraemia (blood infection), osteomyelitis (bone infection), endocarditis (infection of the inner lining of the heart and valves), abscesses in internal organs such as lungs, pneumonia and toxic shock syndrome.
Staph infections can look like a pimple and can be red, swollen and tender. The area can be warm to touch and can have pus that needs to be drained. If the infection gets into the blood, symptoms will include fever, chills and low blood pressure.
In the past, it was less important to determine the underlying source of infection. However with rising antibiotic resistance, it is becoming more important to determine the source of infection or even potential source of infection to quickly and effectively prescribe the appropriate treatment and preventative measures.