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| '''''[[Clostridium difficile]]''''' is a spore-forming, anaerobic, toxin-producing bacterium that is a "common inhabitant of the colon flora in human infants and sometimes in adults. It produces a toxin that causes pseudomembranous enterocolitis in patients receiving antibiotic therapy." ''C. difficile'' superinfection after oral antibiotic therapy, leading to potentially fatal pseudomembranous enterocolitis, has been an increasingly severe public health problem. Indeed, many primary physicians now consider it wise to warn outpatients on antibiotics to seek immediate consultation if they develop severe diarrhea.
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| C. difficile is present at low levels in the gut flora of about 3% of adults. These people however show no symptoms and do not need to be treated. The infection occurs when a person is treated with antibiotics targeted against other bacteria. The disease is for the most part nosocomial. Patients who are hospitalized come in contact and are often inoculated with the bacteria. When the patient is treated with antibiotics, especially those with a broad range of activity, the normal gut flora is disrupted, and C. difficile, with its multi-drug resistance, experiences overgrowth. The bacteria releases large quantities of enterotoxins (toxin A) and cytotoxins (toxin B), causing pseudomembranous enterocolitis.
| | ==Footnotes== |
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| [[Image:img2.gif|thumb|left|250px|scanning electron micrograph of C. difficile]]
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| ==History==
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| In 1935, Hall and O’Toole first isolated the bacteria from the stools of newborns and described it. They named it ''Bacillus difficilis'' because it was hard to isolate and grew very slowly in culture.
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| C. difficile is an important pathogen that is currently increasing in its prevalence world-wide. A complete genome sequence would enable geneticists to come up with a more direct and efficient treatment against the pathogen. The genetic material encodes for antimicrobial resistance, production of toxins (virulence), host interaction (adaptations for survival and growth within the gut environment), and the production of surface structures. The understanding of how these genes interact with their environment will be useful in developing therapies against C. difficile associated diseases.
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| ==Genome Structure== | |
| Sebaihia et al (2006) determined the complete genomic sequence of ''C. difficile'' strain 630, a highly virulent and multidrug-resistant strain. It was found that the genome consists of a circular chromosome of 4,290,252 bp and a plasmid, pCD630, of 7,881 bp. The chromosome encodes 3,776 predicted coding sequences (CDSs), with resistance, virulence, and host interaction genes, while the plasmid carries only 11 CDSs, none of which has any obvious function. ''C. difficile'' has a highly mobile genome, with 11% of the genome consisting of mobile genetic elements, mostly in the form of conjugative transposons. Conjugative transposons are mobile genetic elements that are capable of integrating into and excising from the host genome and transferring themselves, and are responsible for the evolutionary acquisition by C. difficile of genes involved in resistance, virulence, and host interactions. Some of the mobile elements are prophage sequences. Host interaction genes involve genes that code for metabolic capability adaptations for survival and growth within the gut environment.
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| ''[[Clostridium difficile|.... (read more)]]''
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Latest revision as of 10:19, 11 September 2020
1901 photograph of a stentor (announcer) at the Budapest
Telefon Hirmondó.
Telephone newspaper is a general term for the telephone-based news and entertainment services which were introduced beginning in the 1890s, and primarily located in large European cities. These systems were the first example of electronic broadcasting, and offered a wide variety of programming, however, only a relative few were ever established. Although these systems predated the invention of radio, they were supplanted by radio broadcasting stations beginning in the 1920s, primarily because radio signals were able to cover much wider areas with higher quality audio.
History
After the electric telephone was introduced in the mid-1870s, it was mainly used for personal communication. But the idea of distributing entertainment and news appeared soon thereafter, and many early demonstrations included the transmission of musical concerts. In one particularly advanced example, Clément Ader, at the 1881 Paris Electrical Exhibition, prepared a listening room where participants could hear, in stereo, performances from the Paris Grand Opera. Also, in 1888, Edward Bellamy's influential novel Looking Backward: 2000-1887 foresaw the establishment of entertainment transmitted by telephone lines to individual homes.
The scattered demonstrations were eventually followed by the establishment of more organized services, which were generally called Telephone Newspapers, although all of these systems also included entertainment programming. However, the technical capabilities of the time meant that there were limited means for amplifying and transmitting telephone signals over long distances, so listeners had to wear headphones to receive the programs, and service areas were generally limited to a single city. While some of the systems, including the Telefon Hirmondó, built their own one-way transmission lines, others, including the Electrophone, used standard commercial telephone lines, which allowed subscribers to talk to operators in order to select programming. The Telephone Newspapers drew upon a mixture of outside sources for their programs, including local live theaters and church services, whose programs were picked up by special telephone lines, and then retransmitted to the subscribers. Other programs were transmitted directly from the system's own studios. In later years, retransmitted radio programs were added.
During this era telephones were expensive luxury items, so the subscribers tended to be the wealthy elite of society. Financing was normally done by charging fees, including monthly subscriptions for home users, and, in locations such as hotel lobbies, through the use of coin-operated receivers, which provided short periods of listening for a set payment. Some systems also accepted paid advertising.
