Which one of the following organisms is oxidase-positive?

The correct answer is supported by the understanding of the oxidase test, which is a crucial biochemical test used in microbiology to determine the presence of cytochrome c oxidase in bacteria. This enzyme is involved in the electron transport chain and indicates that the organism can utilize oxygen in its metabolic processes.

Pseudomonas aeruginosa, known for its versatility in metabolism and ability to thrive in various environments, is indeed oxidase-positive. This characteristic is one of the defining traits that help differentiate it from other Gram-negative bacilli. The presence of the oxidase enzyme is confirmed by a color change in the test medium when the organism is introduced, marking Pseudomonas aeruginosa as capable of using oxygen as a terminal electron acceptor in aerobic respiration.

In contrast, Acinetobacter calcoaceticus, Stenotrophomonas maltophilia, and Gardnerella vaginalis are considered oxidase-negative, meaning they do not have this enzyme. This distinction is critical in identifying and differentiating bacterial pathogens in clinical microbiology. Understanding these attributes contributes to accurately diagnosing infections and guiding appropriate treatment options.