Bubonic plague laboratory tests

Human specimens
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.

Urinalysis
A urinalysis can also be useful for the determination of Y. Pestis. Urinalysis may show certain results such as:


 * Red blood cell casts
 * Proteinuria
 * Gross hematuria

There has also been the development of rapid urine dipsticks to test for the Y. Pestis antigen.
 * This type of development would be useful in the field if there were an outbreak for rapid identification.