3. A47-year-old woman who had undergone kidney transplantation 2 years earlier presented to the hospital with fever and confusion. Blood cultures obtained on admission were positive with a gram negative rod. A direct identification strip was inoculated from the blood culture that keyed out as Shigella spp., with very few positive reactions. It did not type with Shigella antisera. The test was repeated from a colony the next day, with the same low number of positive reactions. However, the technologist noticed that the original strip had been incubating on the counter and was now positive for urease and a number of sugar fermentation reactions. A new code was determined adding the additional reactions, and the organism keyed out as Yersinia pseudotuberculosis. When the patient was questioned, she admitted that she had been eating unpasteurized imported goat cheese. QUESTIONS a) What tests would you do to confirm the identification of Y. pseudotuberculosis? b) Why did the reactions change in the second incubation period? c) Had this organism been Yersinia pestis, the agent of plague and an agent on the list of potential agents for biologic warfare, what reactions would have been different? d) If the isolate were urease-negative and nonmotile, what should you do next?
3. A47-year-old woman who had undergone kidney transplantation 2 years earlier presented to the hospital with fever and confusion. Blood cultures obtained on admission were positive with a gram negative rod. A direct identification strip was inoculated from the blood culture that keyed out as Shigella spp., with very few positive reactions. It did not type with Shigella antisera. The test was repeated from a colony the next day, with the same low number of positive reactions. However, the technologist noticed that the original strip had been incubating on the counter and was now positive for urease and a number of sugar fermentation reactions. A new code was determined adding the additional reactions, and the organism keyed out as Yersinia pseudotuberculosis. When the patient was questioned, she admitted that she had been eating unpasteurized imported goat cheese. QUESTIONS a) What tests would you do to confirm the identification of Y. pseudotuberculosis? b) Why did the reactions change in the second incubation period? c) Had this organism been Yersinia pestis, the agent of plague and an agent on the list of potential agents for biologic warfare, what reactions would have been different? d) If the isolate were urease-negative and nonmotile, what should you do next?
