Answer :
Final answer:
Increased host immune response would be the evidence least supportive of the hypothesis that urease is a virulence factor in creating Brucella infection. This is because such a response can be more directly linked to the host's natural defense mechanisms rather than the effects of the absent urease in the mutated Brucella strain.
Explanation:
The situation described in your question involves an investigation using mice and a mutated strain of Brucella that lacks the gene necessary for producing urease. The goal is to test the hypothesis that urease plays a role as a virulence factor in establishing Brucella infection. According to your question, the least supportive evidence for this hypothesis would be an increased host immune response to the infection.
This is because an increased immune response is more likely to be a result of the host's defense mechanisms recognizing and responding to the infection, rather than the direct effect of the absence of urease in the Brucella strain. The other options – reduced bacterial colonization in the upper digestive tract, decreased production of ammonia in the host, and lower survival rate of the mutated strain in the host – can all be attributed more directly to the absence of urease production by the Brucella strain.
The urease enzyme is crucial for certain pathogens like Brucella to establish infection in the host, as it effectively neutralizes stomach acids, allowing the bacteria to survive in the harsh gastric environment and subsequently infect the host.
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