Yersinia pestis infection laboratory findings: Difference between revisions
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==Laboratory Findings== | ==Laboratory Findings== | ||
Following a thorough history and physical exam, patients suspected to be infected by the plague require a confirmation of the initial diagnosis. Plague is a quarantinable diseases covered under international regulations. In the United States, reporting of suspicious cases and sending collected material to specialized labs and to the State Health Department are mandatory procedures. | |||
The diagnosis of plague is confirmed only by the following 2 techniques: | |||
*''Y. pestis'' antibody titers, requiring a 4x increase between the acute and the convalescent phases. | |||
*Lysis of ''Y. pestis'' by unique bacteriophages in bacterial culture | |||
===Collection of Samples=== | |||
First, collection of '''blood specimens''', '''lymph node aspirates''' from buboes, '''sputum samples''', and '''tracheal swabs''' are needed before the administration of antibiotics. Additionally, '''cerebrospinal fluid (CSF) collection''' is required in cases suspected to have meningeal complications of plague. | |||
====Blood Samples==== | |||
Blood should be sent for analysis, culture, and peripheral smear. | |||
*If clinically stable, at least 3 samples for culture within 45 minutes should be collected before antibiotic administration. | |||
*Serological diagnosis using passive hemagglutination test (PHA) using ''Y. pestis'' F1 antigen. If samples are retrieved within 3-4 weeks of symptoms onset, serological confirmation is highly sensitive. | |||
The use of rapid detection tests, such as ELISA and PCR assays to detect F1 antigen are not routinely used yet. However, they may be helpful to confirm cases of suspected plague when gold standard confirmatory tests are not available. | |||
====Lymph Node Aspiration==== | |||
Bubo aspiration, using a small sterile syringe containing sterile saline, is performed by insertion of the needle into the central part of the bubo. If original aspiration fails, injection of the sterile saline inside the syringe may be performed and then aspirated. The aspirate is then used as follows: | |||
*2 slide preparations for routine staining, using Giemsa (or Wayson) method and for gram stain. | |||
*2 slide preparations for direct fluorescent antibody (FA) testing | |||
Aspirate should also be used for culture using sheep blood agar, brain-heart infusion (BHI) broth, and MacConkey agar. | |||
====Other Specimens==== | |||
All aspirates and specimens from CSF, tracheal swab, and sputum also need to be tested using gram stain, Giemsa stain, and FA testing. | |||
*[[Gram staining|Gram's stain]]s can confirm the presence of [[gram-negative]] rods, and in some cases the identification of the double-curved shape. | *[[Gram staining|Gram's stain]]s can confirm the presence of [[gram-negative]] rods, and in some cases the identification of the double-curved shape. | ||
*Anti-F1 serology test can differentiate between different species of Yersinia | *Anti-F1 serology test can differentiate between different species of Yersinia | ||
Revision as of 20:37, 25 July 2014
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Assistant Editors-In-Chief: Esther Lee, M.A.
Laboratory Findings
Following a thorough history and physical exam, patients suspected to be infected by the plague require a confirmation of the initial diagnosis. Plague is a quarantinable diseases covered under international regulations. In the United States, reporting of suspicious cases and sending collected material to specialized labs and to the State Health Department are mandatory procedures.
The diagnosis of plague is confirmed only by the following 2 techniques:
- Y. pestis antibody titers, requiring a 4x increase between the acute and the convalescent phases.
- Lysis of Y. pestis by unique bacteriophages in bacterial culture
Collection of Samples
First, collection of blood specimens, lymph node aspirates from buboes, sputum samples, and tracheal swabs are needed before the administration of antibiotics. Additionally, cerebrospinal fluid (CSF) collection is required in cases suspected to have meningeal complications of plague.
Blood Samples
Blood should be sent for analysis, culture, and peripheral smear.
- If clinically stable, at least 3 samples for culture within 45 minutes should be collected before antibiotic administration.
- Serological diagnosis using passive hemagglutination test (PHA) using Y. pestis F1 antigen. If samples are retrieved within 3-4 weeks of symptoms onset, serological confirmation is highly sensitive.
The use of rapid detection tests, such as ELISA and PCR assays to detect F1 antigen are not routinely used yet. However, they may be helpful to confirm cases of suspected plague when gold standard confirmatory tests are not available.
Lymph Node Aspiration
Bubo aspiration, using a small sterile syringe containing sterile saline, is performed by insertion of the needle into the central part of the bubo. If original aspiration fails, injection of the sterile saline inside the syringe may be performed and then aspirated. The aspirate is then used as follows:
- 2 slide preparations for routine staining, using Giemsa (or Wayson) method and for gram stain.
- 2 slide preparations for direct fluorescent antibody (FA) testing
Aspirate should also be used for culture using sheep blood agar, brain-heart infusion (BHI) broth, and MacConkey agar.
Other Specimens
All aspirates and specimens from CSF, tracheal swab, and sputum also need to be tested using gram stain, Giemsa stain, and FA testing.
- Gram's stains can confirm the presence of gram-negative rods, and in some cases the identification of the double-curved shape.
- Anti-F1 serology test can differentiate between different species of Yersinia
- Polymerase chain reaction (PCR) can be used to identify Yersinia pestis