Which organism is described as tiny, weak staining, gram-negative coccobacilli?

The organism that is described as tiny, weak staining, gram-negative coccobacilli is Francisella tularensis. This bacterium is known for its small size and pleomorphic nature, often requiring specific staining techniques for clear visualization under a microscope. Its weak staining characteristics can pose challenges in laboratory identification, as traditional Gram staining may not provide a definitive result.

Francisella tularensis is significant in medical microbiology due to its pathogenicity and its association with tularemia, a disease that can affect humans and a variety of animals. The identification of this organism in clinical specimens often necessitates specialized culture methods or serological tests to confirm its presence.

The other organisms listed have different characteristics that do not match the description provided. For example, Escherichia coli is a well-known gram-negative bacillus, while Haemophilus influenzae is also a small gram-negative coccobacillus but is typically better staining than described. Brucella species, although they are also gram-negative coccobacilli, are more commonly associated with specific clinical presentations and may not fit the weak staining detail as closely as Francisella tularensis.