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The encapsulated, Gram-positive, coccoid bacteria have a distinctive morphology on Gram stain, lancet-shaped diplococci. They have a polysaccharide capsule that acts as a virulence factor for the organism; more than 100 different serotypes are known, and these types differ in virulence , prevalence , and extent of drug resistance .
Streptococcus pneumoniae is the most common bacterial cause of pneumonia in all age groups except newborn infants. Streptococcus pneumoniae is a Gram-positive bacterium that often lives in the throat of people who do not have pneumonia. Other important Gram-positive causes of pneumonia are Staphylococcus aureus and Bacillus anthracis.
Streptococcus is a genus of gram-positive or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales (lactic acid bacteria), in the phylum Bacillota. [2] Cell division in streptococci occurs along a single axis , thus when growing they tend to form pairs or chains, which may appear bent or twisted.
The Gram stain is used by microbiologists to place bacteria into two main categories, Gram-positive (+) and Gram-negative (-). Gram-positive bacteria have a thick layer of peptidoglycan within the cell wall, and Gram-negative bacteria have a thin layer of peptidoglycan.
Reagents used for Lancefield grouping. Lancefield grouping is a system of classification that classifies catalase-negative Gram-positive cocci based on the carbohydrate composition of bacterial antigens found on their cell walls. [1]
Gram staining differentiates bacteria by the chemical and physical properties of their cell walls. Gram-positive cells have a thick layer of peptidoglycan in the cell wall that retains the primary stain, crystal violet. Gram-negative cells have a thinner peptidoglycan layer that allows the crystal violet to wash out on addition of ethanol.
Streptolysin O is an oxygen-sensitive cytotoxin secreted by most Group A streptococcus (GAS) and Streptococcus dysgalactiae; it interacts with cholesterol in the membrane of eukaryotic cells (mainly red and white blood cells, macrophages, and platelets), usually resulting in β-hemolysis under the surface of blood agar. Streptolysin S is an ...
Occurring in pairs or chains, streptococci are found to be Gram-positive (although older cultures may lose this characteristic), non-mobile, non-spore forming, and catalase-negative. [2] Bacteriophages, also known as phages, of streptococcus within different parameters of temperature, pH, and salinity maintain successfully stable and are lytic. [3]