The list of medical tests mentioned in various sources as used in the diagnosis of Plague includes:
Appropriate specimens should be examined for evidence of plague if a person resides in, or has a recent travel history to, plague-infected areas; has been bitten by fleas; and presents with symptoms suggestive of plague (fever, lymphadenopathy). Specimens should be obtained from appropriate sites for isolating the bacteria. The preferred specimen for microscopic examination and isolation from a bubonic case is material from the affected bubo, which should contain numerous organisms. Blood cultures should be taken whenever possible. Organisms may be seen in blood smears if the patient is septicemic, while blood smears taken from suspected bubonic plague patients are usually negative for bacteria. Bacteria may be intermittently released from affected lymph nodes into the bloodstream; therefore, a series of blood specimens taken 10-30 minutes apart may be productive in the isolation of Y. pestis. Sputum/throat smears taken from pneumonic plague patients may contain too many other organisms to be of diagnostic value if only Wayson stain is used; these smears should be stained as well with the more specific fluorescent-antibody (FA) test. Bronchial/tracheal washing should be taken from suspected pneumonic plague patients; throat specimens are not ideal for isolation of plague since they often contain many other bacteria that can mask the presence of plague. In cases where live organisms are unculturable, e.g., in specimens taken postmortem, lymphoid tissues, lung and bone marrow samples may yield evidence of plague infection by FA test or by detection of Y. pestis DNA.
Specimens intended for culture should be taken before initiation of antibiotic treatment. Specimens are inoculated on general laboratory media and into laboratory mice for isolation; a thin smear is made from the remaining materials for examination by fluorescent microscopy. If a specimen is suspected to contain mixed flora, passage of the material through laboratory mice will increase the likelihood of recovery of a pure Y. pestis culture. Plague bacilli express a unique diagnostic envelope glycoprotein called the Fraction 1 (F1) antigen or capsular antigen at >33°C; this unique envelope antigen is the primary target antigen used for plague diagnostic FA and antibody tests. Plague bacilli are susceptible to lysis by a specific bacteriophage at both 25°C and 37°C. Plague bacilli are relatively inactive by standard enteric biochemical reactions; therefore, identification by biochemical profiles should be used as a supplemental diagnostic test. If a patient has been treated with a static antibiotic (e.g., tetracycline) for more than 4 days, bacterial cultures should be incubated for more than 5 days to give organisms a chance to recover. In case cultures yield negative results, serologic testing is advised. One serum specimen should be taken as early in the illness as possible to be followed by a second sample 1-4 months after antibiotic therapy has ceased.
Animal/flea specimens: Likewise, appropriate tissues should be taken from animals for detection of Y. pestis. Lymphoid tissues should be removed for testing of the presence of F1 antigen by FA and by culture. Bone marrow from dessicated animal carcasses may yield positive results when other tissues are not available. In addition, serum and blood specimens may be taken for detection of antibody by agglutination. Fleas should be identified and may be placed in pools for tituration and examination. Titurated flea materials may be inoculated into laboratory mice for isolation of plague bacteria and for examination of mouse tissues by FA for expression of F1. Fleas or flea pool material may be directly examined by FA if the samples are pre-incubated at 37°C for 24 hours to encourage F1 antigen expression. The serum from inoculated laboratory mice may be examined for presence of antibody to F1. For serosurveillance of plague in animal populations, blood may be soaked and dried onto filter paper strips and sent to the laboratory for the detection of F1 antibody. Lastly, as with human specimens, in cases where no cultures or serum specimens are available for testing, both animal and flea material may be tested by polymerase chain reaction (PCR) to determine if plague DNA is present in the specimens. (Source: excerpt from Plague Diagnosis: DVBID)
16 MEDICAL BOOKS ONLINE! Review excerpts from medical books online, free, without registration, for more information about diagnostis of Plague.
Because plague is rare in the United States, it's commonly overlooked until after the patient dies or multiple cases develop. Characteristic buboes and a history of exposure to rodents in known endemic areas strongly suggest bubonic plague.
CONFIRMING DIAGNOSIS Stained smears and cultures of Y. pestis obtained from a needle aspirate of a small amount of fluid from skin lesions confirm this diagnosis.
Postmortem examination of a guinea pig inoculated with a sample of blood or purulent drainage allows isolation of the organism. Other laboratory findings include a white blood cell count of over 20,000/µl with increased polymorphonuclear leukocytes and hemoagglutination reaction (antibody titer) studies. Diagnosis should rule out tularemia, typhus, and typhoid.
In pneumonic plague, diagnosis requires a chest X-ray to show fulminating pneumonia and stained smear and culture of sputum to identify Y. pestis. Other bacterial pneumonias and psittacosis must be ruled out. Stained smear and blood culture containing Y. pestis are diagnostic in septicemic plague. However, cultures of Y. pestis grow slowly; so, in suspected plague (especially pneumonic and septicemic plagues), treatment should begin without waiting for laboratory confirmation. For a presumptive diagnosis of plague, a fluorescent antibody test may be ordered.
Source: Professional Guide to Diseases (Eighth Edition), 2005
Because plague is rare in the United States, it’s commonly overlooked until after the patient dies or multiple cases develop.
Characteristic buboes and a history of exposure to rodents strongly suggest bubonic plague. Stained smears and cultures of Y. pestis (obtained from a small amount of fluid aspirated from skin lesions) confirm this diagnosis.
Postmortem examination of a guinea pig inoculated with a sample of blood or purulent drainage allows isolation of the organism. Other labora-tory findings include a white blood cell count over 20,000/µl with increased polymorphonuclear leukocytes and hemoagglutination reactions (increased antibody titer).
Diagnosis should rule out tularemia, typhus, and typhoid.
Stained smear and blood culture containing Y. pestis are diagnostic in septicemic plague.
Diagnosis of pneumonic plague requires a chest X-ray to show fulminating pneumonia and stained smear and culture of sputum to identify Y. pestis. Other bacterial pneumonias and psittacosis must be ruled out.
UNDER STUDY: Researchers have developed a rapid diagnostic test for bubonic and pneumonic plague. It uses monoclonal antibodies to the F antigen of Y. pestis and has a sensitivity and specificity of 100%. Results from the test are available within 15 minutes and have a shelf life of 21 days at 60° F (15.6° C).
Source: Handbook of Diseases, 2003
Pitfalls:
Source: The 5-Minute Pediatric Consult, 2008
What do you think about the features of this website? Take our user survey and have your say:
Next articles:
Tools & Services:
Medical Articles:
Search Specialists by State and City
By using this site you agree to our Terms of Use. Information provided on this site is for informational purposes only; it is not intended as a substitute for advice from your own medical team. The information on this site is not to be used for diagnosing or treating any health concerns you may have - please contact your physician or health care professional for all your medical needs. Please see our Terms of Use.
Copyright © 2009 Health Grades Inc. All rights reserved.
When someone-- a sibling, parent or grandparent-- passes away, it's often hard to know what the youngest members of the family are going through....
As adults, we all comprehend the fact that our parents will die eventually. But the reality of that event often has much more emotional impact than...