Yersinia pestis is a Gram negative pleomorphic coccobacillus in the family Enterobacteriaceae. It is both aerobic and facultatively anaerobic. The bacteria gives an unusual staining pattern which is bipolar and is said to resemble a "safety pin"
Y. pestis grows in temperature ranges from 4 to 37C with an optimum growth temperature of 28C. It will grow on unenriched or blood agar, or on beef heart infusion broth. Growth is slow, and colonies of 1-2 mm will form within 48 hours. Colonies have a grayish, nonmucoid, granular surface.
The bacteria produces several outer membrane proteins linked with pathogenicity. Given calcium in the media at 37C the bacteria exhibits good growth, but expression of these Yersinia outer membrane proteins (yops) is reduced. If denied calcium at 37C, bacterial growth is retarded, and pathogenic factors, the yops, are produced. Only a few have functions which are known, but these functions include evading phagocytosis, interfering with the host cell signal transduction, inhibiting inflammatory mediators, and rearranging host cell actin uptake. Some of these proteins are produced only at specific temperatures, including the protein capsule which is expressed only at 37C and helps prevent phagocytosis.
Y. pestis is the organism responsible for three different forms of plague: bubonic, septicemic, and pneumonic. Y. pestis can survive briefly in soil, for approximately 1 week in soft tissue, and when frozen, can survive for years. The major vector for the organism is the flea, Order Siphonaptera, especially the rat flea, Xenopsylla cheopis. X. cheopis is a common parasite of the black rat, Rattus rattus, and can also feed on other hosts, including humans. This was the cause of the Justinian Plague from 558 to 590AD, the "Black Plague" in 14th century Europe, Austria in 1711, the Balkans from1770-1772, and recently in Surat, India in 1994.
Y. pestis grows in temperature ranges from 4 to 37C with an optimum growth temperature of 28C. It will grow on unenriched or blood agar, or on beef heart infusion broth. Growth is slow, and colonies of 1-2 mm will form within 48 hours. Colonies have a grayish, nonmucoid, granular surface.
The bacteria produces several outer membrane proteins linked with pathogenicity. Given calcium in the media at 37C the bacteria exhibits good growth, but expression of these Yersinia outer membrane proteins (yops) is reduced. If denied calcium at 37C, bacterial growth is retarded, and pathogenic factors, the yops, are produced. Only a few have functions which are known, but these functions include evading phagocytosis, interfering with the host cell signal transduction, inhibiting inflammatory mediators, and rearranging host cell actin uptake. Some of these proteins are produced only at specific temperatures, including the protein capsule which is expressed only at 37C and helps prevent phagocytosis.
Y. pestis is the organism responsible for three different forms of plague: bubonic, septicemic, and pneumonic. Y. pestis can survive briefly in soil, for approximately 1 week in soft tissue, and when frozen, can survive for years. The major vector for the organism is the flea, Order Siphonaptera, especially the rat flea, Xenopsylla cheopis. X. cheopis is a common parasite of the black rat, Rattus rattus, and can also feed on other hosts, including humans. This was the cause of the Justinian Plague from 558 to 590AD, the "Black Plague" in 14th century Europe, Austria in 1711, the Balkans from1770-1772, and recently in Surat, India in 1994.
No comments:
Post a Comment