Yersinia pestis infection laboratory findings

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Yazan Daaboul; Serge Korjian

Overview

Bubonic plague is diagnosed by gram stain and culture of aspirated material from suppurative lymph nodes. 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. In the United States, reporting of suspicious cases and sending collected material to specialized labs with expertise in Plague testing and to the State Health Department are mandatory procedures.

Laboratory Findings

Following a thorough history and physical exam, patients suspected to be infected by the plague, such as a patient presenting with fever living in an endemic region, require a confirmation of the initial diagnosis. Plague is a quarantinable disease covered under international regulations. Patients with bubonic plague suspected to have secondary pneumonic plague should be placed in respiratory isolation until after 48 hours of effective antibiotic administration. In the United States, reporting of suspicious cases and sending collected material to specialized labs with expertise in Plague testing and to the State Health Department are mandatory procedures.

According to the "2014 Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue and Soft Tissue Infections", The diagnosis of bubonic plague is confirmed only by gram stain and culture of aspirated material from suppurative lymph nodes.

Other suggested confirmatory tests that have been frequently used include the following:

• A 4x increase in Y. pestis antibody titer between acute and convalescent phase serum samples
• Lysis of Y. pestis by unique bacteriophage in culture

Common laboratory findings may not always be present. They include the following:

Blood Work-Up

• Leukoyctosis and neutrophilia with left shift
• Thrombocytopenia
• Elevated D-dimer
• Elevated transaminase and bilirubin concentrations
• Elevated creatinine
• Hypoglycemia
• Elevated Y. pestis F1 antigen

Urine Work-Up

• Proteinuria

Peripheral Smear

• Rod-shaped bacteria on Giemsa stain and "safety pin" (or bipolar) appearance on Wayson stain
• Toxic granulations and Dohle bodies

Gram Stain

• Small gram-negative coccobacilli

Culture of Fluids

• Positive for Y. pestis

Cerebrospinal Fluid Analysis

• Pleocytosis with polymorphonuclear leukocyte predominance
• Limulus test confirms endotoxin

Collection of Samples

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 1 mL 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.

Gallery

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  Yersinia pestis bacteria cultured on a xylose-lysine-deoxycholate (XLD) agar medium 24hrs (10x mag). Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Yersinia pestis bacteria cultured on a sheep blood agar (SBA) medium 72hrs (10x mag). Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Yersinia pestis bacteria cultured on a sheep blood agar (SBA) medium 24hrs (10x mag). Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Yersinia pestis bacteria cultured on sheep blood agar (SBA) medium 120hrs. Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Yersinia pestis bacteria cultured on a sheep blood agar (SBA) medium, for a 120hrs (20x mag). Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Yersinia pestis bacteria cultured on a sheep blood agar (SBA) medium 120hrs (5x mag). Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Yersinia pestis bacteria cultured on a sheep blood agar (SBA) medium 120hrs (10x mag). Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Yersinia pestis bacteria cultured on a MacConkey agar (MAC) medium 48hrs (10x mag). Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Yersinia pestis bacteria cultured on a MacConkey agar (MAC) medium 24hrs (10x mag). Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Yersinia pestis bacteria cultured on a MacConkey agar (MAC) medium 24 hrs (10x mag). Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Yersinia pestis bacteria cultured on a cefsulodin-Irgasan-novobiocin (CIN) agar medium 48hrs (20x mag). Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Yersinia pestis bacteria on a chocolate agar plate 120hrs. Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Yersinia pestis bacteria cultured on a blood agar plate (BAP) 24hrs (10x). Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Yersinia pestis bacteria cultured on a blood agar plate (BAP) 24hrs (10x mag). Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Yersinia pestis bacteria cultured on sheep blood agar (SBA) 48hrs (10x). Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Yersinia pestis bacteria, cultured on MacConkey agar (MAC) medium 72hrs (10x mag). Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Gram-negative Yersinia pestis bacteria, cultured on sheep blood agar (SBA) medium 24hrs (10x mag). Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Photomicrograph depicting a blood smear that revealed the presence of Gram-negative Yersinia pestis plague bacteria. Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Histopathologic changes in a lymph node tissue sample in a case of fatal human plague. From Public Health Image Library (PHIL).

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  Gram-negative Yersinia pestis bacteria, grown on a medium of chocolate agar 24hrs. From Public Health Image Library (PHIL).

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  Gram-negative Yersinia pestis bacteria, grown on SBA 72hrs. From Public Health Image Library (PHIL).

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  Gram-negative Yersinia pestis bacteria, grown on SBA 72hrs. From Public Health Image Library (PHIL).

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  Gram-negative Yersinia pestis bacteria, grown on chocolate agar 72hrs. From Public Health Image Library (PHIL).

References