streptococcus

The Columbia Encyclopedia, 6th ed.

streptococcus

streptococcus (strĕp´təkŏk´əs), any of a group of gram-positive bacteria, genus Streptococcus, some of which cause disease. Streptococci are spherical and divide by fission, but they remain attached and so grow in beadlike chains. The incidence and severity of streptococcal diseases decreased dramatically after the introduction of antibiotics (penicillin, erythromycin, and selected cephalosporins are all effective against the organisms), but the medical community was shaken by the arrival in the late 1980s of several severe forms of streptococcal infection and by the emergence of several drug-resistant strains (see drug resistance).

Types of Streptococci

Streptococci are classified into the alpha, beta, or gamma groups, according to their action on blood cells. Streptococci of the alpha group (e.g., the viridans and S. pneumoniae) cause some destruction (hemolysis) of red blood cells. The beta group are more destructive of red blood cells; they also produce toxic substances that affect white blood cells and the clotting properties of blood. Members of these two groups are sometimes called hemolytic (red blood cell–destroying) streptococci. The beta-hemolytic streptococci are often further classified into several lettered groups, called Lancefield groups for R. C. Lancefield, the scientist who originated the scheme in the 1930s. Group A hemolytic streptococci are responsible for most human streptococcal disease; group B hemolytic streptococci can cause serious problems, such as septicemia and meningitis, especially in newborns. The gamma group, or nonhemolytic group, does not affect red blood cells. Enterococci (usually harmless bacteria that inhabit the intestines) and lactococci (bacteria used in starter cultures in the production of fermented dairy products) used to be considered a part of the Streptococcus genus but are now placed in their own genera.

S. pneumoniae and Viridans Infections

The viridans are normal inhabitants of the body and are usually harmless; however, they can contribute to tooth decay. Streptococcus pneumoniae is the most common cause of otitis media in children. It can also cause meningitis and pneumonia. The S. pneumoniae diseases are sometimes referred to as pneumococcal diseases. The development of drug-resistant strains of pneumococci has caused concern in the medical community. Vaccination against pneumococcal pneumonia is recommended for very young children and older persons; the vaccine inoculates against the most prevalent strains of S. pneumoniae.

Group A Streptococcal Infections

Group A hemolytic streptococci cause over a dozen diseases, including some pneumonias, erysipelas (a generalized body infection), upper respiratory infections, wound infections, and puerperal fever. Scarlet fever is also a streptococcal, or strep, infection; the rash is a response to a toxin produced by the bacteria that cause strep throat. Rheumatic fever follows an initial Group A streptococcal infection: proteins of the streptococcal cells stimulate antibody formation by the body (see immunity), and these antistreptococcal antibodies are believed to react with and damage many tissues of the body, especially heart muscle. Kidney disease (acute glomerulonephritis) is another complication of streptococcal infections. Some extremely serious Group A streptococcal infections began to emerge or reemerge in the late 1980s. Streptococcal toxic shock syndrome is a rapidly progressing infection, similar to septicemia or toxic shock syndrome, that usually infects people in their 20s or 30s. It causes blood pressure to fall rapidly and organs to fail. Necrotizing fasciitis is a quickly spreading infection of the flesh and muscle caused by toxins released by S. pyrogenes. Such bacteria are popularly called "flesh-eating bacteria."

Group B Streptococcal Infections

Group B streptococci are a common cause of infection in babies, pregnant women, the elderly, and immunologically compromised adults. They are especially serious in newborns, in whom they can cause sepsis, meningitis, or pneumonia. Group B streptococci are often present in people who show no symptoms of disease; these people are said to be "colonized." Many infants are colonized before or during birth by mothers who unknowingly carry the bacteria. A small percentage of these develop disease, which can be life-threatening or can lead to lifelong neurological problems.

Bibliography

See M. P. Starr et al., ed., The Prokaryotes: A Handbook on Habitats, Isolation and Identification of Bacteria (1981).

Notes for this article

Add a new note
If you are trying to select text to create highlights or citations, remember that you must now click or tap on the first word, and then click or tap on the last word.
One moment ...
Default project is now your active project.
Project items

Items saved from this article

This article has been saved
Highlights (0)
Some of your highlights are legacy items.

Highlights saved before July 30, 2012 will not be displayed on their respective source pages.

You can easily re-create the highlights by opening the book page or article, selecting the text, and clicking “Highlight.”

Citations (0)
Some of your citations are legacy items.

Any citation created before July 30, 2012 will labeled as a “Cited page.” New citations will be saved as cited passages, pages or articles.

We also added the ability to view new citations from your projects or the book or article where you created them.

Notes (0)
Bookmarks (0)

You have no saved items from this article

Project items include:
  • Saved book/article
  • Highlights
  • Quotes/citations
  • Notes
  • Bookmarks
Notes
Cite this article

Cited article

Style
Citations are available only to our active members.
Sign up now to cite pages or passages in MLA, APA and Chicago citation styles.

(Einhorn, 1992, p. 25)

(Einhorn 25)

1

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

Cited article

streptococcus
Settings

Settings

Typeface
Text size Smaller Larger Reset View mode
Search within

Search within this article

Look up

Look up a word

  • Dictionary
  • Thesaurus
Please submit a word or phrase above.
Print this page

Print this page

Why can't I print more than one page at a time?

Full screen

matching results for page

Cited passage

Style
Citations are available only to our active members.
Sign up now to cite pages or passages in MLA, APA and Chicago citation styles.

"Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn, 1992, p. 25).

"Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn 25)

"Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences."1

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

Cited passage

Welcome to the new Questia Reader

The Questia Reader has been updated to provide you with an even better online reading experience.  It is now 100% Responsive, which means you can read our books and articles on any sized device you wish.  All of your favorite tools like notes, highlights, and citations are still here, but the way you select text has been updated to be easier to use, especially on touchscreen devices.  Here's how:

1. Click or tap the first word you want to select.
2. Click or tap the last word you want to select.

OK, got it!

Thanks for trying Questia!

Please continue trying out our research tools, but please note, full functionality is available only to our active members.

Your work will be lost once you leave this Web page.

For full access in an ad-free environment, sign up now for a FREE, 1-day trial.

Already a member? Log in now.