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''Streptococcus pneumoniae'', or pneumococcus, is a Gram-positive, alpha-hemolytic, facultative anaerobic member of the genus ''Streptococcus''. A significant human pathogenic bacterium, ''S. pneumoniae'' was recognized as a major cause of pneumonia in the late 19th century, and is the subject of many humoral immunity studies. ''S. pneumoniae'' resides asymptomatically in the nasopharynx of healthy carriers. The respiratory tract, sinuses, and nasal cavity are the parts of host body that are usually infected. However, in susceptible individuals, such as elderly and immunocompromised people and children, the bacterium may become pathogenic, spread to other locations and cause disease. ''S. pneumoniae'' is the main cause of community acquired pneumonia and meningitis in children and the elderly, and of septicemia in HIV-infected persons. The methods of transmission include sneezing, coughing, and direct contact with an infected person. Despite the name, the organism causes many types of pneumococcal infections other than pneumonia. These invasive pneumococcal diseases include bronchitis, rhinitis, acute sinusitis, otitis media, conjunctivitis, meningitis, bacteremia, sepsis, osteomyelitis, septic arthritis, endocarditis, peritonitis, pericarditis, cellulitis, and brain abscess. ''S. pneumoniae'' is one of the most common causes of bacterial meningitis in adults and young adults, along with ''Neisseria meningitidis'', and is the leading cause of bacterial meningitis in adults in the USA. It is also one of the top two isolates found in ear infection, otitis media. ''Pneumococcal'' pneumonia is more common in the very young and the very old. It also is a major bacterium for invasive diseases like pneumonia and meningitis in South Asian children 12 years of age, though the evidence is of low quality and scarce. ''S. pneumoniae'' can be differentiated from ''Streptococcus viridans'', some of which are also alpha-hemolytic, using an optochin test, as ''S. pneumoniae'' is optochin-sensitive. ''S. pneumoniae'' can also be distinguished based on its sensitivity to lysis by bile, the so-called "bile solubility test". 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 90 different serotypes are known, and these types differ in virulence, prevalence, and extent of drug resistance. ==History== In 1881, the organism, known later in 1886 as the pneumococcus〔 for its role as an (agent ) of pneumonia, was first isolated simultaneously and independently by the U.S. Army physician George Sternberg〔.〕 and the French chemist Louis Pasteur.〔.〕 The organism was termed ''Diplococcus pneumoniae'' from 1920 because of its characteristic appearance in Gram-stained sputum. It was renamed ''Streptococcus pneumoniae'' in 1974 because it was very similar to streptococci.〔 〕 ''S. pneumoniae'' played a central role in demonstrating genetic material consists of DNA. In 1928, Frederick Griffith demonstrated transformation of life, turning harmless pneumococcus into a lethal form by co-inoculating the live pneumococci into a mouse along with heat-killed, virulent pneumococci. In 1944, Oswald Avery, Colin MacLeod, and Maclyn McCarty demonstrated the transforming factor in Griffith's experiment was DNA, not protein, as was widely believed at the time. Avery's work marked the birth of the molecular era of genetics. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Streptococcus pneumoniae」の詳細全文を読む スポンサード リンク
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