<\/span><\/h2>\nSeveral tests are performed in a laboratory to establish or confirm the diagnosis of bacterial skin. infection<\/span>. Although a complete history and examination of the patient are vital, laboratory tests can help the doctor reach a diagnosis.<\/p>\nthe culture<\/span> of bacterial species with antibiotic susceptibility testing is considered the gold standard laboratory test.<\/p>\n<\/span>Skin samples for bacterial tests.<\/span><\/h2>\nSkin samples can be collected in the following ways.<\/p>\n
\n- A dry sterile cotton swab is rubbed on the suspected skin site, for example, blistered or dry skin lesions or pustules<\/span>.<\/li>\n
- A moist swab is taken from a mucous membrane<\/span> surface, such as inside the mouth.<\/li>\n
- \nAspiration<\/span> of fluid\/pus from a skin injury<\/span> using a needle and syringe (a swab is more likely to produce organism<\/span>)<\/li>\n
- A skin biopsy<\/span>: a small sample of skin removed under local anesthetic<\/span>.<\/li>\n<\/ul>\n\n
<\/span>bacterial skin swab<\/span><\/h5>\n<\/section>\n\n\n
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bacterial skin swab<\/p>\n<\/p><\/div>\n<\/section>\n
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\n<\/div><\/div><\/div><\/div>\n
<\/span>What is meant by cultivation? bacteria<\/span>?<\/span><\/h2>\nCultivation or growth of bacteria is most often done by brushing the skin swab onto sheep blood agar plates and exposing them to different conditions. The bacteria that grow depend on the medium used to culture the sample, the temperature for incubation<\/span>, and the amount of oxygen available.<\/p>\n\n- An obligate aerobe can only grow in the presence of oxygen.<\/li>\n
- An obligate anaerobe cannot grow at all in the presence of oxygen.<\/li>\n<\/ul>\n\n
<\/span>Bacterial culture on an agar plate.<\/span><\/h5>\n<\/section>\n\n\n
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forearm sample<\/p>\n
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fingertip swatch<\/p>\n<\/p><\/div>\n<\/section>\n
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<\/span>What is antibiotic susceptibility testing?<\/span><\/h2>\nAntibiotic susceptibility testing determines which antibiotics inhibit<\/span> The growth of bacteria that have been cultured. This information allows selection of the most appropriate antibiotic to treat a particular infection. Antibiotic susceptibility tests are used to determine:<\/p>\n\n- The effectiveness of particular antibiotics against particular bacteria<\/li>\n
- Whether the bacteria are resistant to selected antibiotics<\/li>\n
- Identify patterns of resistance to bacterial antibiotics.<\/li>\n<\/ul>\n
<\/span>What is a Gram stain?<\/span><\/h2>\nA Gram stain uses a series of stains or dyes on a sample, followed by inspection under a light microscope to detect and identify bacteria as Gram-positive or Gram-negative. A Gram stain can be done on the original sample, but is usually done on cultured bacteria after transferring a colony of bacteria from the agar plate to a glass microscope slide.<\/p>\n
\n- A Gram-positive bacterium<\/span> appears purple due to the crystal violet dye that adheres to the cell wall.<\/li>\n
- A Gram-negative bacterium appears red because it is counteracted with a red dye such as saffron.<\/li>\n<\/ul>\n
The Gram stain also identifies the shape and behavior of the bacteria.<\/p>\n
\n- Coconuts are round in shape<\/li>\n
- The bacilli are rod-shaped.<\/li>\n
- Some bacteria form clumps while others form chains<\/li>\n<\/ul>\n\n
<\/span>Gram-positive bacilli: corynebacteria cultured from the skin of the forearm*<\/span><\/h5>\n<\/section>\n\n\n
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Gram stain of corynebacteria cultured from the skin of the forearm.<\/p>\n<\/p><\/div>\n<\/section>\n
<\/div>\n
* Note the palisade\/parallelism of cells in the 'Chinese letters' formation<\/p>\n
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<\/span>What other tests can be done with bacterial cultures?<\/span><\/h2>\n<\/span>\nCoagulase<\/span> test<\/span><\/h3>\ncoagulase is a enzyme<\/span> produced by certain bacteria that convert fibrinogen<\/span> to fibrin<\/span> and is seen as clustering of cells in plasma<\/span>. Coagulase test differentiates positive coagulase Staphylococcus aureus<\/em> coagulase negative staphylococci.<\/p>\n<\/span>Catalase test<\/span><\/h3>\nCatalase is an enzyme that breaks down hydrogen peroxide into hydrogen and oxygen. The bacterial sample is added to a test tube of hydrogen peroxide. The production of bubbles (oxygen) indicates a positive result. The catalase test differentiates catalase-positive staphylococci and micrococci from catalase-negative streptococci.<\/p>\n
<\/span>What blood tests are done in bacterial infections?<\/span><\/h2>\nBlood tests require a blood sample accessed with a needle from a vein. Examples of those requested for bacterial infection include:<\/p>\n
\n- Complete blood count \u2013 a bacterial infection often increases the white blood cell count with neutrophilia<\/li>\n
- \nC-reactive protein<\/span> (CRP<\/span>) \u2013 this rises above 50 in severe bacterial infections<\/li>\n
- Procalcitonin \u2013 a marker of generalized<\/span> septicemia<\/span><\/span> due to bacterial infection<\/li>\n
- \nSerology<\/span> \u2013 tests 10 to 14 days apart to determine the immune response to a particular organism<\/li>\n
- Rapid plasma reactivation test (RPR) (and others) \u2013 if syphilis is suspected<\/li>\n
- Blood culture: if it is high fever<\/span> > 38\u00b0C<\/li>\n<\/ul>\n
<\/span>\nPolymerase chain reaction<\/span> (PCR<\/span>)<\/span><\/h2>\nPCR involves isolating and amplifying lengths of bacteria DNA<\/span> from a sample of skin, blood, or other tissue. The DNA is compared with bacterial DNA from organisms<\/span>thus identifying the species. It is useful for slow-growing bacteria such as anaerobic<\/span> bacteria and mycobacteria (tuberculosis and atypical<\/span> mycobacteria), as they cannot be cultured by standard methods.<\/p>\n<\/span>Enzyme-linked immunosorbent assay (ELISA)<\/span><\/h2>\nELISA can test for specific organisms by detecting bacteria antigen<\/span> during an infection or antibacterial antibody<\/span>. Detection of the antibody confirms contact with an organism at some point, but is not necessarily the reason for a current infection.<\/p>\nELISA is rarely used for the detection of skin bacteria. It can be used to detect:<\/p>\n
\n- \nBorrelia burgdorferi<\/em> in Lyme disease\n<\/li>\n
- \nTreponema pallidum<\/em> in syphilis<\/li>\n<\/ul>\n<\/section>","protected":false},"excerpt":{"rendered":"
\u00bfPor qu\u00e9 necesitamos pruebas de laboratorio para bacteriano infecciones? Se realizan varias pruebas en un laboratorio para establecer o confirmar el diagn\u00f3stico de una piel bacteriana. infecci\u00f3n. Aunque un historial…<\/p>","protected":false},"author":8,"featured_media":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","format":"standard","meta":{"footnotes":""},"categories":[204],"tags":[],"class_list":["post-16589","wiki","type-wiki","status-publish","format-standard","category-glosario-definiciones"],"_links":{"self":[{"href":"https:\/\/doctorhoogstra.com\/en\/wp-json\/wp\/v2\/wiki\/16589","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/doctorhoogstra.com\/en\/wp-json\/wp\/v2\/wiki"}],"about":[{"href":"https:\/\/doctorhoogstra.com\/en\/wp-json\/wp\/v2\/types\/wiki"}],"author":[{"embeddable":true,"href":"https:\/\/doctorhoogstra.com\/en\/wp-json\/wp\/v2\/users\/8"}],"replies":[{"embeddable":true,"href":"https:\/\/doctorhoogstra.com\/en\/wp-json\/wp\/v2\/comments?post=16589"}],"version-history":[{"count":0,"href":"https:\/\/doctorhoogstra.com\/en\/wp-json\/wp\/v2\/wiki\/16589\/revisions"}],"wp:attachment":[{"href":"https:\/\/doctorhoogstra.com\/en\/wp-json\/wp\/v2\/media?parent=16589"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/doctorhoogstra.com\/en\/wp-json\/wp\/v2\/categories?post=16589"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/doctorhoogstra.com\/en\/wp-json\/wp\/v2\/tags?post=16589"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}