Which biochemical test is needed to differentiate Burkholderia cepacia from S. maltophilia?

To differentiate between Burkholderia cepacia and Stenotrophomonas maltophilia, the combination of tests that includes examining pigment production on blood agar, performing an oxidase test, and assessing DNase activity is particularly effective.

Burkholderia cepacia is known to produce a yellow pigment on blood agar and can also exhibit oxidase positivity, whereas S. maltophilia typically does not produce pigment on blood agar and is oxidase-negative. The presence of DNase activity can further aid in distinguishing the two, as it is a characteristic feature of B. cepacia. Thus, this combination of tests provides clear and distinct biochemical traits that help microbiologists accurately identify and differentiate between these two similar species.

The other tests listed in the other options do not effectively distinguish between these two organisms. For example, pigment production on MacConkey agar or tests for specific carbohydrate utilization might not give clear differentiation, as both organisms can have overlapping biochemical profiles.