What are the microbiological examination methods?

sample

Because plague is highly contagious, strict aseptic operation must be carried out when collecting specimens. According to the disease type, lymph node puncture fluid, tissue fluid of swollen parts, pus, blood and sputum were taken. Human and animal corpses can be taken from liver, spleen, lung, diseased lymph nodes and heart blood. Extract bone marrow from an old corpse. Send the collected specimens to a special laboratory with strict protective measures for inspection, and it is forbidden to operate in a general laboratory.

Direct smear microscopy

Except for blood samples, smears or prints are generally needed, which are fixed with methanol after drying, stained with Gram or Lv Meilan, and examined under a microscope. In different materials, the size and morphology of bacteria are very different. In addition to the typical morphology, it is often seen that bacteria are polymorphic and need attention.

Isolation, culture and identity

Blood samples should be put in broth for enrichment culture first. Blood agar plates are generally used for separation and culture. After 24 hours at 28℃, smaller dewdrop colonies can be seen. After continuous culture, the colony will increase to 1 ~ 2 mm, the center will be thick and the periphery will gradually become thinner. Suspected colonies were identified by smear staining microscopy, phage lysis test, serum agglutination test and specific fluorescent antibody staining.

Serum test

Can be use for detecting Yersinia pestis antigen or specific antibody. Sensitive and specific detection methods include ELISA, solid-phase radioimmunoassay, SPA synergistic agglutination test and so on.

Detection nucleic acid

Detection of Yersinia pestis nucleic acid by DNA probe hybridization or PCR is helpful for the diagnosis of plague. The sensitivity of PCR is extremely high, and 10 Yersinia pestis infection in fleas can be detected by PCR technology.

Diagnostic examination

Diagnosis: It depends on the patient's contact history and lung involvement, and the etiological diagnosis depends on the Gram staining and culture of sputum, blood or lymph node aspirate. Direct fluorescein-labeled antibody staining can provide rapid etiological diagnosis if conditions permit.