MDH Flow Chart for Rule-out and
Referral of Yersinia pestis
Public Health Laboratory - Emergency Preparedness and Response Unit
601 Robert St. N. PO Box 64899, St. Paul, MN 55164
http://www.health.state.mn.us/divs/phl/labep/index.html
Colony Morphology on SBA
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Slow growing at 35˚C Grows better at 25-28˚ C
1-2 mm gray-white, opaque, “hammered copper” shiny
Older colonies develop “fried egg” appearance smooth
edges
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Gram Stain Morphology
1.0 x 0.5 µm gram negative bacilli
May exhibit bipolar staining
Classical Biochemical
Reactions
Automated
Identification
Oxidase
Organism identified
as Y. pestis
Positive
Organism identified
as gram neg rod
other than Y. pestis
Negative
Not Y. pestis
WARNING: Automated
Identification must be
verified by “classical
biochemical reactions”
(if not available in your
lab, send to MDH-PHL)
Urea and Indole
Positive
ID systems may key out
Y. pestis as other species
(e.g. Shigella, H2S-neg
Salmonella, Acinetobacter, &
Y. pseudotuberculosis)
Rule out Y. pestis if Low
Probability ID
Negative
Not Y. pestis
Motility
Positive
Negative
At 25-28˚C and 35˚C
Not Y. pestis
Other key Y.pestis reactions—run
these if available in your lab:
Nitrate +(85), Glucose +,
Mannitol +, L-Rhamnose –,
Melibiose – (20)
08/03/2015
REFER ISOLATE:
Cannot Rule Out Y. pestis
Call MDH-PHL at 612-282-3723
24/7