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The
Bacterium
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Fluorescence
antibody positivity is seen as bright, intense green staining around
the bacterial cell.
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Classification:
Yersinia was
formerly classified in the family Pasteurellaceae, but based on
DNA- DNA hybridization similarities to Escherichia coli, the Yersinia
group has been reclassified as members of the Enterobacteriaceae
family (Farmer, 1995). Differentiation of the Enterobacteriaceae
family members is based on biochemical and antigenic profiles. More recently,
nucleic acid techniques have been applied to assist the definition of
genera and species within this family; hence, as more techniques are applied,
newly defined genetic relationships sometimes lead to changes in classification.
Though there are 11 named species in the genus Yersinia, only 3
are considered important human pathogens: Y. pestis, the etiologic
agent of plague, and the enteropathogenic strains, Y. pseudotuberculosis
and Y. enterocolitica. Y. pseudotuberculosis is the closest
genetic relative to Y. pestis but can be distinguished from the
plague bacteria by its clinical manifestations and by laboratory test
results. Both Y. pestis and Y. pseudotuberculosis do not
frequently infect humans in contrast to Y. enterocolitica, which
may be more commonly found in clinical specimens.
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Wayson
stain of Yersinia pestis. Note the characterisitc "safety
pin" appearance of the bacteria.
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References:
Perry RD, Fetherston
JD. Yersinia pestis--etiologic agent of plague. Clin Microbiol
Rev, 1997;10:35-66.
Farmer
JJ. Enterobacteriaceae: introduction and identification. In: Murray
PR, Baron EJ, Pfaller MA, Tenover FC, Yolken RH, eds. Manual of Clinical
Microbiology. 6th editon. Washington DC: ASM Press 1995:438-48.
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