The laboratory diagnosis of plague

Several diagnostic methods for Yersinia pestis infections are available including culture, serological, molecular and chromatographic assays. These techniques may be applied to human clinical specimens as well as rodents and other animals sampled in the course of plague surveillance. All the methods have their merits depending on the time available and the information required. Time is of the essence in the diagnosis of plague. Rapid diagnostic techniques capable of detecting Y. pestis directly in clinical samples, infected animal tissue and fleas will facilitate speedy diagnosis. The culture methods are reliable but relatively slow and insensitive. The serological ELISA tests are sensitive but in the case of the antibody assay, rely on a detectectable humoral immune response. Antigen can be detected at an earlier stage in the infection. DNA probes lack sensitivity, as 10(5)-10(6) organisms are needed for reliable detection. The PCR is sensitive and can detect as few as 10 Y. pestis organisms, but cannot distinguish between live and dead bacteria. A recently-developed chromatographic assay is very specific and sensitive and takes only 10 minutes to obtain a result, but thorough field testing is awaited.