CZ:Featured article/Current: Difference between revisions

From Citizendium
Jump to navigation Jump to search
imported>Chunbum Park
No edit summary
imported>Chunbum Park
(Clostridium difficile)
Line 1: Line 1:
In their 2010 report, the  Economic Advisors to the President referred  the recent economic downturn as the '''[[Great Recession]]''', suggesting a parallel with the Great Depression of the 1930s. Like the Great Depression - and unlike other recessions - it had a simultaneous impact on most of the world's economies. But in other respects it was unique. There had been no precedent for such extensive damage to the world's financial system, nor for the coordinated  measures that were taken to avert what was feared to be its imminent collapse.  
'''''[[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.


Although, according to the generally accepted definition of the term, the recession ended in most countries when economic growth resumed during 2009, its damaging effects upon the major economies are expected to persist beyond 2011, and its ultimate  cost may amount to as much as a whole year's ouput of every country in the world.  
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.  


The Great Recession has prompted a re-examination of beliefs concerning the functioning of markets comparable to that which followed the Great Depression.
[[Image:img2.gif|thumb|left|250px|scanning electron micrograph of C. difficile]]
==History==
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.


=====Introduction=====
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.
Explanations of the causes of the recession and accounts of contemporary debates concerning policy responses are available in the articles on the subprime mortgage crisis, the crash of 2008 and the recession of 2009, together with timelines linked to contemporary reports.


=====Overview=====
==Genome Structure==
During the 1980s there was a widespread re-appraisal of the regulations that had been introduced in response to the financial instability that developed during  the Great Depression. A consensus had already  emerged that many  regulations were economically harmful, as a result of which programmes of deregulation had been adopted. The reappraisal concluded that the financial regulations of the 1930s had become unnecessary because recently-developed monetary policy could be used to counter any further signs of instability. Ongoing programmes of banking deregulation that had prevented investment banks  from engaging in branch banking, insurance or mortgage lending were dropped, and reserve requirements were relaxed or removed.
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.


After the mid-1980s came  a twenty-year  period that has been termed the great moderation, during which recessions had been less frequent and less severe than in previous periods, and during which there  been  a great deal of successful financial innovation.
''[[Clostridium difficile|.... (read more)]]''
 
In the United States, that period was characterised by massive capital inflows and the large-scale availability of credit to households,  and by  2007 personal savings rates dropped to 2 per cent of disposable income from their previous average of 9 per cent and there was a house price boom  that has since been categorised as a bubble.
The bursting of that bubble in 2007, and the downgrading by the credit rating agencies of large numbers of internationally-held financial assets created what came to be known as the subprime mortgage crisis, which led, in turn,  to the  financial crash of 2008 and the failure of several of the world's largest banks.  The loss of investors' confidence caused by  failure of the ''Lehman Brothers'' investment bank in September 2008,  resulted in a credit crunch. The resulting fall in spending struck the major economies at a time when they were already suffering from the impact of a supply shock in which  a surge in commodity prices was causing households to reduce their spending.  Economic forecasters had been  expecting a mild downturn: what actually happened  was the global slump in ecomomic activity that has come to be known as the Great Recession. 
 
Although the  trigger that set the recession  off had been  the malfunction of a part of  the  United States  housing market, it soon emerged that a more fundamental problem had been  the fact  that  the financial innovations that had been  richly rewarding traders in the world's financial markets,  had also  been threatening their collective survival. The  crucial nature of that threat for the stability of the world economy  arose from the fact that it had become  dependent upon the services of a well-functioning international financial system.
''[[Great Recession|.... (read more)]]''
{|align="center" cellpadding="5" style="background:lightgray; width:60%; border: 1px solid #aaa; margin:10px; font-size: 92%;"
| Supplements to this article include an annotated[[Great Recession/Timelines|''' chronology ''']] of the main events of the recession; and  accounts of the  [[Great Recession/Addendum| '''regional impact''']] of the recession.
|}

Revision as of 18:43, 24 August 2011

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.

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.

scanning electron micrograph of C. difficile

History

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.

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.

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.

.... (read more)

Retrieved from "https://citizendium.org/wiki/index.php?title=CZ:Featured_article/Current&oldid=829574"