Streptococcus, << `strehp` tuh KOK uhs >> , is any of a group of round bacteria that look, under a microscope, like strings of beads. The plural form of the word is streptococci << `strehp` tuh KOK sy >> . Some kinds of streptococci are harmless. But pathogenic (disease-causing) streptococci can cause many illnesses.
Bacteriologists classify some groups of streptococci as hemolytic << hee muh LIHT ihk >> bacteria. When these bacteria are grown in laboratories, they harm or destroy red blood cells in their culture medium (source of food). There are two chief types of hemolytic streptococci, alpha-hemolytic and beta-hemolytic. Alpha-hemolytic streptococci damage red blood cells. Some of these bacteria are found in the mouth and are linked to tooth decay. A related species, Streptococcus pneumoniae, is a major cause of bacterial pneumonia, ear infections, and sinus infections.
Loading the player...Tooth decay
Beta-hemolytic streptococci completely destroy red blood cells. Biologists recognize many groups of beta-hemolytic streptococci. One of the groups—group A—causes most streptococcal diseases in human beings. Group A streptococcal infections include strep throat, a skin infection called impetigo << `ihm` puh TY goh >> , scarlet fever, and septicemia << `sehp` tuh SEE mee uh >> (which means blood poisoning). Group A infections also can lead to rheumatic fever.
Some doctors think the number of severe group A infections began to increase in the 1980’s. These illnesses include necrotizing fasciitis << NEHK ruh tyz ihng fash ee EYE tihs >> —sometimes called the “flesh-eating” infection because it can destroy infected tissue.
Doctors prescribe disease-fighting drugs called antibiotics to treat streptococcal infections. But due to the use and overuse of these drugs, several types of streptococci have developed resistance to antibiotics. Some kinds of Streptococcus pneumoniae, for example, became resistant to penicillin.
