Which organism is described as a short Gram-negative bacillus with oxidase variable and X factor negative?

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Multiple Choice

Which organism is described as a short Gram-negative bacillus with oxidase variable and X factor negative?

A quick way to identify this profile is through how fastidious Gram-negative bacteria are tested for growth needs and enzyme activity. Pasteurella multocida is a small, short Gram-negative bacillus (coccobacillus) that does not require X factor (hemin) to grow, so it is X factor negative. Its oxidase reaction can vary depending on the test conditions, which fits the description of oxidase variable. This combination helps distinguish it from organisms like Haemophilus species, which need X factor (and are not X factor negative), and from Salmonella or Acinetobacter, which are typically oxidase negative. Therefore, the described organism aligns with Pasteurella multocida.

A quick way to identify this profile is through how fastidious Gram-negative bacteria are tested for growth needs and enzyme activity. Pasteurella multocida is a small, short Gram-negative bacillus (coccobacillus) that does not require X factor (hemin) to grow, so it is X factor negative. Its oxidase reaction can vary depending on the test conditions, which fits the description of oxidase variable. This combination helps distinguish it from organisms like Haemophilus species, which need X factor (and are not X factor negative), and from Salmonella or Acinetobacter, which are typically oxidase negative. Therefore, the described organism aligns with Pasteurella multocida.

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