Streptococcus

(noun)

A spherical, gram-positive bacterium of the genus Streptococcus. Although commonly found benignly in the human mouth and gut, and though many species are non-pathogenic, other species can cause diseases including strep throat and more serious conditions.

Related Terms

Examples of Streptococcus in the following topics:

  • Group B Streptococcus Colonization

    • Group B streptococcus is part of the natural microflora in some people, but can sometimes cause life-threatening infections.
    • Group B streptococcus (GBS), also called streptococcus agalactiae or simply strep B, is part of the natural genital and intestinal microflora in some people.
    • The bacteria is gram-positive streptococcus, and possesses the group B antigen from the Lancefield classification.
    • Describe the pathogenic characteristics, symptoms and diagnostic test used for Group B streptococcus (GBS)

  • Bacterial Pneumonias

    • Bacteria are the most common cause of community-acquired pneumonia (CAP), with Streptococcus pneumoniae isolated in nearly 50% of cases .
    • Alcoholism is associated with Streptococcus pneumoniae, anaerobic organisms and Mycobacterium tuberculosis; smoking facilitates the effects of Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, and Legionella pneumophila.
    • 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.
    • The bacterium Streptococcus pneumoniae, a common cause of pneumonia, imaged by an electron microscope

  • Scarlet Fever

    • Scarlet fever is caused by a bacteriophage that infects Streptococcus pyogenes.
    • Scarlet fever is caused by an erythrogenic toxin, a substance produced by the bacterium Streptococcus pyogenes (group A strep. ) when it is infected by a certain bacteriophage.
    • Scarlet fever is caused by secretion of pyrogenic (fever inducing) exotoxins by the infected Streptococcus.

  • Bacterial Skin Diseases

    • It is primarily caused by Staphylococcus aureus and sometimes by Streptococcus pyogenes.
    • Erysipelas is an acute streptococcus bacterial infection of the upper dermis and superficial lymphatics.
    • Most cases of erysipelas are due to Streptococcus pyogenes (also known as beta-hemolytic group A streptococci), although non-group A streptococci can also be the causative agent.
    • Beta-hemolytic, non-group A streptococci include Streptococcus agalactiae, also known as group B strep or GBS.
    • Group A Streptococcus and Staphylococcus are the most common of these bacteria, which are part of the normal flora of the skin, but normally cause no actual infection while on the skin's outer surface.

  • Tooth and Gum Infections

    • The bacteria most responsible for dental cavities are the mutans streptococci, most prominently Streptococcus mutans and Streptococcus sobrinus, and lactobacilli.
    • The mouth contains a wide variety of oral bacteria, but only a few specific species of bacteria are believed to cause dental caries: Streptococcus mutans and Lactobacilli among them.
    • Lactobacillus acidophilus, Actinomyces viscosus, Nocardia spp., and Streptococcus mutans are most closely associated with caries, in particular root caries.
    • The oral cavity of the newborn baby does not contain bacteria but rapidly becomes colonized with bacteria such as Streptococcus salivarius.
    • With the appearance of the teeth during the first year, colonization by Streptococcus mutans and Streptococcus sanguinis occurs as these organisms colonize the dental surface and gingiva.

  • Rheumatic Fever

    • Rheumatic fever is an inflammatory disease that occurs following a Streptococcus pyogenes infection, such as streptococcal pharyngitis (strep throat) or scarlet fever, that affects the peri-arteriolar connective tissue.
    • During a Streptococcus infection, mature antigen-presenting cells, such as B cells, present the bacterial antigen to CD4-T cells which differentiate into helper T2 cells.
    • In turn, Helper T2 cells activate the B cells to become plasma cells and induce the production of antibodies against the cell wall of Streptococcus.
    • Photomicrograph of Streptococcus pyogenes bacteria, 900x Mag.

  • Pharyngitis

    • The most common is Group A streptococcus, but others include Corynebacterium diphtheriae, Neisseria gonorrhoeae, Chlamydophila pneumoniae, and Mycoplasma pneumoniae.
    • Streptococcal pharyngitis, more commonly known as strep throat, is caused by group A beta-hemolytic streptococcus (GAS).

  • Direct Damage

    • Examples of bacteria that will damage tissue by producing toxins, include, Corynebacterium diphtheriae and Streptococcus pyogenes.
    • Streptococcus pyogenes is associated with strep throat and "flesh-eating disease. " The bacteria produce enzymes which function in disrupting fibrin clots.

  • Microbes and Dairy Products

    • The main genera that belong to the lactic acid bacteria group are: Lactobacillus, Leuconostoc, Lactococcus, Pediococcus and Streptococcus.
    • Classic yogurt is the result of the fermentation of two main bacterial species: Lactobacillus bulgaricus and Streptococcus thermophilus.
    • Other fermented and widely consumed cultured dairy products include kefir (lactic acid bacteria and yeasts are used for the fermentation), sour cream (fermented cream), cultured buttermilk (fermented cow's milk with Streptococcus lactis or Lactobacillus bulgaricus only).

  • Fusobacteria

    • In individuals infected with Fusobacterium necrophorum and additonal Fusobacterium as well, a sore develops in the throat due to infection by a bacterium of the Streptococcus genus.