A Brucella isolate that does not produce H2S and does not require CO2 is probably which species?

In this scenario, the correct identification of the Brucella species is based on specific biochemical characteristics. The isolate described does not produce hydrogen sulfide (H2S) and does not require carbon dioxide (CO2) for growth.

Brucella melitensis is known for requiring specific growth conditions but can also be cultured under atmospheric conditions without supplementary CO2. Additionally, Brucella melitensis is typically associated with non-H2S producing strains, making it compatible with the described isolate.

Brucella abortus, Brucella suis, and Brucella canis have different growth requirements and biochemical profiles that would suggest varying abilities to produce H2S or having specific CO2 requirements. For instance, Brucella abortus and Brucella suis are more likely to be associated with H2S production in certain conditions. Brucella canis, while it shares similarities with the other species, tends to have a profile that does not align as closely with the non-H2S and non-CO2 requiring characteristics stated in the question.

Therefore, the characteristics of the isolate strongly align with Brucella melitensis, confirming its identification in this context.