Streptococcus bacteria are spherical, Gram-positive, and resistant to acidic conditions. They are divided into 18 Lancefield groups, with Group A, B, Viridans, and Pneumonia S being the most medically concerning. Group A can cause sore throat, scarlet fever, and sepsis, while Group B can be dangerous for newborns. Viridans can cause dental infections and endocarditis, and Pneumonia S can cause pneumonia, sinusitis, and meningitis.
Streptococcus bacteria are a genus of coccus, or spherical, Gram-positive, concatenated bacteria belonging to the lactic acid bacteria (LAB) group. Individual strep cells can be round or ovoid and all lack the enzyme catalase. Because these cells divide in a single plane, streptococci occur in pairs or chains.
Like many other types of bacteria in the phylum firmicute, streptococcus bacteria stain dark blue or purple when subjected to a Gram stain due to the composition of its cell wall. This is what is meant by Gram-positives. As a member of the lactic acid bacteria group, this bacterium is resistant to acidic conditions and thrives without oxygen or with oxygen levels below the oxygen concentration in the air.
Streptococcus bacteria are divided into eighteen literate groups, called Lancefield groups. American bacteriologist Rebecca Craighill Lancefield developed this method of classifying streptococci in 1933 based on the antigens, or antibody-producing substances, present in the cell wall of the streptococcal bacteria under study. However, several types of strep do not react to Lancefield grouping and must be classified using hemolysis, which monitors the complete degradation of the bacterium in a blood solution.
The viridans streptococcus group is non-haemolytic or only partially decomposes, resulting in the green spot responsible for the name “viridans”. This large and diverse group of streptococci does not yet have a reliable taxonomy (classification) or nomenclature. Many types of strep throat can cause illness and infection in humans, while many others are harmless. Group A Streptococcus, Group B Streptococcus, Viridans Streptococcus, and Pneumonia S are the types most commonly of medical concern.
Group A streptococcus (GAS), or S pyogenes, is one of the most common pathogens in humans. A GAS infection can affect several locations on the body and are often classified by location. One of the best known of these is sore throat. Strep affects the throat and causes several symptoms, including severe sore throat, swollen tonsils, nausea, headache, and yellow and white patches in the throat.
GAS can be fatal as a cause of puerperal fever or sepsis in women after childbirth. Sepsis is when a microbe enters the bloodstream, possibly causing a severe systemic reaction. GAS was also responsible for bouts of scarlet fever which, like puerperal fever, are now controlled through better hygiene and antibiotics. In the skin, GAS can cause impetigo, cellulitis and erysipelas. GAS infections can also cause pneumonia, meningitis, tonsillitis, septic arthritis and toxic shock syndrome, among other illnesses.
Group B streptococcus (GBS), or S agalactiae, bacteria are frequently found in the urogenital tracts and rectum of women of childbearing age. Complications can arise in women with compromised immune systems, but it is most commonly significant when it is passed on to babies during delivery. A GBS infection of a newborn can cause meningitis or sepsis, which can lead to death or long-term hearing loss. Neonatal meningitis presents differently than adult meningitis, with symptoms of vomiting and fever. For this reason, neonatal meningitis often goes undiagnosed and can be fatal.
Streptococcus viridans is often responsible for dental infections and plaque formation. This type of bacteria, along with group C, F, G, and especially group D, can cause endocarditis, especially when the valves of the heart have previously been damaged. Endocarditis is inflammation of the inner layer of the heart, known as the endocardium.
Streptococcus pneumoniae, or pneumococcus, is the most common cause of invasive bacterial infection of children and the elderly. It can cause pneumonia, sinusitis and meningitis, among other diseases. Streptococcus pneumoniae can cause both lobar pneumonia, which affects an entire lung lobe, usually in young adults, and bronchial pneumonia, which affects the alveoli, tending to the elderly or children.
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