Which organism is identified based on growth as gram-negative rods resembling 'closed safety pins' in a patient with fever after a camping trip?

The organism described as gram-negative rods resembling 'closed safety pins' is Yersinia pestis. This bacterium is known for causing plague and is transmitted to humans primarily through flea bites or contact with infected animals. The characteristic morphology of Yersinia pestis when stained and observed under a microscope often provides a distinct appearance that can help clinicians make an initial identification.

The mention of fever after a camping trip is clinically relevant, as Yersinia pestis is associated with exposure to wild rodents or their fleas, which are more commonly encountered in outdoor settings. The 'closed safety pin' appearance refers to the bipolar staining pattern seen in this microorganism, particularly when using the Wright or Giemsa stain.

In contrast, while the other organisms listed may also cause infections, they do not exhibit the same characteristic morphology or epidemiological association with camping. Klebsiella pneumoniae and Proteus vulgaris, for example, are not typically associated with such a specific growth pattern. Morganella morganii, although a gram-negative rod, does not have the same epidemiological link to camping or the 'closed safety pin' appearance typical of Yersinia pestis. Thus, Yersinia pestis is the most appropriate identification for the scenario provided.