EXAMPLE+Streptococcus+pyogenes

= // Streptococcus pyogenes // =

Taxonomic Classification
 Kingdom: Bacteria Phylum: Firmicutes Class: Bacilli Order: Lactobacillales Family: Streptococcaceae Genus: Streptococcus Species: Pyogenes 

Background
 // Streptococcus pyogenes // is a species of //Streptococci// bacteria that belong to a group known as GAS (Group A Streptococci). //S. pyogenes// is known for its infectious properties and can cause a huge variety of diseases ranging from minor skin infections to sepsis to toxic shock syndrome. There are an estimated over 700 million cases per year worldwide of severe //S. pyogenes// infections. There is typically a 25% mortality associated with severe infections, which is largely due to failure to properly diagnose the infection in a timely manner.  About 5-15% of healthy people harbor the bacterium in their respiratory tract but remain unaffected by it until they are immonucompromised. Clinically, differentiating among the groups of Steptococci is enormously important due to the fact that they can each cause different diseases and require different antibiotics. Group A strep are defined by the presence of antigen A on their cell wall, which can be detected by different serological tests. //S. pyogenes// not only displays the antigen A, but also something called the M protein that can be used to further classify sub groups of //S. pyogenes.// It should be no surprise that both antigen A and the M protein, along with an array of other surface antigens and exotoxins, are the reasons that the bacterium has enormous potential to cause human disease. 

**Cell Structure**
 // Streptococcus pyogenes // is a spherical, Gram positive bacterium. It is non-motile and non-spore forming. //S. pyogenes// can be differentiated from other group A strep by the presence of M factor on its cell well. Cells divide on a plane and exist in pairs or in chains.





Methods of identification
 There are many methods to rapidly and reliably indentify //Streptococcus// species and differentiate among the subgroups in a species. One of the broad identifiers is looking at the hemolytic properties. //Streptococcus pyogenes// is what is known as beta-hemolytic, meaning that it can lyse red blood cells. Due to this attribute, if you plate it on blood agar, the colonies appear to have clear “halos” surrounding them (see image below). This is due to a chemical called hyaluronic acid that is present in a capsule around the cells.  To get into differentiating among smaller subgroups: There are several different very closely related//Streptococcus// groups, and they can typically be differentiated by testing which polysaccharides and other antigens are displayed on their cell surface. One such test is the Lancefield antigen test, which is typically applied to categorize the //Streptococcus// into one of many different subgroups by assessing which antigens are displayed on the cell surface. Strep colonies are smeared onto a small card, and a colored reagent with antigen specific antibodies is poured over the smear. If the antibodies bind—or agglutinate, forming clumps—with the antigens in the strep smear, this means that the antigen in question is present (see lower image ).  Getting into even greater specifics, //Streptococcus pyogenes// can be divided further still into subgroups. There is a lot of variation in the sequence of the //emm// gene, the gene that produces the M protein. Sequencing this gene to identify polymorphisms is now commonly used to group //S. pyogenes// into subgroups, and this test has largely replaced older biochemical tests. There have been over 140 //emm// types identified so far.

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Metabolism
<span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"><span style="font-family: arial,helvetica,sans-serif; font-size: 13px;"> //S. pyogenes// is a facultative anaerobe that needs enriched    <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;">,  <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"><span style="font-family: arial,helvetica,sans-serif; font-size: 13px;">   blood-contain ing medium to grow. It is design at ed as "catalase negative" which means that it does not produce the enzyme catalase      <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;">, <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> an enzyme that catalyzes the reaction of hydrogen peroxide to water and oxygen. This is clinically significa nt, as a test for th is enzyme is a common clinical diagnostic tool. <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;">

Infectious Diseases
<span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> <span style="font-family: arial,helvetica,sans-serif; font-size: 13px;">The genome of //S. pyogenes// has been sequenced and was found to have more than 40 putative virulence genes. This is possibly why this bacterium is responsible for what might be the most diverse array of disease than known to be caused by any other bacterium. <span style="font-family: arial,helvetica,sans-serif; font-size: 13px;"> Most infections can be treated with an oral or intramuscular regimen of most b eta-lactams such as penicillin or ampicillin, or other broad spectru m antibiotics such as v ancomycin or c lin d a mycin (though resistance to clindamycin is on the rise). Diseases it can cause include:

<span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> <span style="font-family: arial,helvetica,sans-serif; font-size: 13px;">** ·  Impetigo**-- a superficial infection of the skin. Can be treated with antibiotics. <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> <span style="font-family: arial,helvetica,sans-serif; font-size: 13px;">** ·  Cellulitis**-- an deep tiss ue infection <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> ** ·  Strep throat**--an infection of the throat. Can be treated with antibiotics. However, if left untreated it can lead to Rheumatic fever an d even endocar ditis. <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> **  ·  Toxic shock syndrome (TSS)**-- a couple speci es of bacteria can cause this. Symptoms include fever, dizziness, confusion, and mucous membrame hyperemia. It can r e sult in organ failur e. Typically,               //S. pyogenes//            cause d TSS is a result of a skin infection. If properly diagnosed, it can be treated with antibiotics. I f untreated or treated to late, can result i n organ failure and death. <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> ** ·  Necrotizing fasciitis**-- A disease that starts off as a superficial wound, but if that wound happens to have <span style="font-family: arial,helvetica,sans-serif; font-size: 13px;">        //S. pyogene s //          with certain virulence genes, it can release exotoxins that destroy the host tissue. This is commonly known as "flesh eating bacteria", which a is a misnomer, because nothing is actually eating the tissue but rendering it necrotic with the release of exotoxins. Several other organisms can be responsible for this d isease as well. Because of the swiftness and seriousness of this infection, a mputation of infected parts is often treatment. Symptoms include pain/discoloration that is disproportionate to the sever ity of a superficial wound, and sometimes even fever. Unfortunately, there is no "magic bullet" indicator of necrotizing fasciitis, but a number of fact ors that if present at certain levels in combination with the proper sym ptoms, ind i cate that infection is likely. If a medical professi onal suspects necrotizing fa sci itis, he or she will look at six serological measurements: C reactive protein, white blood cell count, hemoglobin, sodium, creatnine, and glucose. These fact ors are s core d, and a score of 6 or greater result in a diagnosis of the disease. The table below details the criteria : <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;">

<span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> As mentioned, strep throat is one of the more common and usually minor forms of strep in fection. The following video is a a creative and informative dramatization of a strep throat infection, from patient symptoms to diagnosis, to treatment- all acted out by Barbies. <span style="background-color: #ffffff; display: block; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;">             Watch Video  <span style="background-color: #ffffff; display: block; font-family: 'Lucida Grande',Arial,sans-serif; font-size: 15px;">Streptococcus pyogenes Infection [Barbie Version]
 * <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;">Duration: (7:49) **
 * <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;">User: **<span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> angle3

// **Streptococcus pyogenes** // **and the mammalian immune system** <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> <span style="font-family: arial,helvetica,sans-serif; font-size: 13px;">One of the reasons //S. pyogenes// is so virulent is due in its ability to evade or interact with the mammalian immune system. Ways it can evade/interact with the immune system include: <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"><span style="font-family: arial,helvetica,sans-serif; font-size: 13px;">** · ** **M protein** allows it to evade phagocytosis by immune cells <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> ** ·** **Hyaluronic acid capsule** allows it to not only evade phagocytosis, but also may help it adhere to epithelial cells. Having this capsule can aid in obscuring the cell’s surface antigens, preventing immune cell recognition and subsequent response. <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> **·** **Fibro** **n** **ectin binding protein** and lipoteichoic acid help to adhere to mammalian cells <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;">
 * **  **·**   **  **Pyrogenic toxin** is an exotoxin produced ca n cause the rash associated with scarlet fever and can also contribute to toxi c shock syndro me.

//Streptococcus pyogenes// and super antigens
<span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;">    Super antigens a re antigens produced by        <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;">         //S. pyogenes//         <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;">        that tri gger the immune system. Lots of pathogens release antigens as a normal part of infectio n, and the immune system relies on a very specific "lock and key" f it for the presence of a foreign ant i gen to trigger an immune response. Th e "lock and key" fit ensure that only the right cells (cells that have a specific fit for the a ntigen you want to target) are stimulated. A super antigen will hyper - stimulate any and all immune cells, regardless for how well they will target an antigen.An analogy for this would be: the normal immune response is like a very good team of special forces that can adeptly ta rget and attack invaders. The super antigen immune response is like a large but poorly trained army that attack with all their ammunition at once. T his all out immune system "attack" can result in sympto m s like severe fever and chills. See diagram below for a depiction of how s uperantigens work.

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<span style="font-family: Arial,Helvetica,sans-serif; font-size: 13pt;">Antibiotic resistance
<span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> <span style="font-family: arial,helvetica,sans-serif; font-size: 13px;">Recently, there has been a rise in //S. pyogenes// th at  are resistant to broad spectrum antibiotics such as m acrol i de and c lindomycin. Interestingly,  <span style="font-family: arial,helvetica,sans-serif; font-size: 13px;">//S. pyogenes// is on e of the few speci es of pathogenic bacteria that have yet to de velop resistance to beta-lactams. Bacitracin is one of the antibiotics that //S. pyogenes// is sensitive to, while many other speci es of strep are resistant to it. Thus, sensitivity to Bacitracin can be a goo d diagnostic to di feere ntiate          <span style="font-family: arial,helvetica,sans-serif; font-size: 13px;">//S. pyogenes//       from other species of strep. Below is a video demonstrating how one might do such a test. <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> <span style="background-color: #ffffff; display: block; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> <span style="font-family: arial,helvetica,sans-serif; font-size: 13px;"> Watch Video Bacitracin test for Streptococcus pyogenes ** Duration: (0:51) **
 * User: ** markmicrobiology - ** Added: ** 8/12/11

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<span style="font-family: Arial,Helvetica,sans-serif;"> References
<span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> [] <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> [] <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> [] <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> [|http://www.caparonlab.wustl.edu/groupastrep.htm] [] <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> Albrich, W; Monnet, DL; Harbarth, S (2004). <span style="font-family: arial,helvetica,sans-serif; font-size: 13px;"> [|"Antibiotic selection pressure and resistance in Streptococcus pneumoniae and Streptococcus pyogenes"]. //Emerging Infect. Dis.// **10** (3): 514–7. <span style="font-family: arial,helvetica,sans-serif; font-size: 13px;"> [|doi] : <span style="font-family: arial,helvetica,sans-serif; font-size: 13px;"> [|10.3201/eid1003.030252]. <span style="font-family: arial,helvetica,sans-serif; font-size: 13px;"> [|PMC] [|3322805]. <span style="font-family: arial,helvetica,sans-serif; font-size: 13px;"> [|PMID] [|15109426]. <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> [] <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> [|http://wwwnc.cdc.gov/eid/article/9/10/03-0042_article.htm] <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> [|http://www.antimicrobe.org/b239rev-table%202.pdf] <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> [|http://www.bcmj.org/article/streptococcus-pyogenes-alive-and-well] <span style="background-color: #ffffff; font-family: 'Lucida Grande',Arial,sans-serif; font-size: small;"> [|http://www.emergency-medicine-tutorials.org/Home/medical-3/infectious-diseases-1/bacterial/necrotising-fascitis/lrinec-scoring-system-for-necrotising-fascitis]