Which statement is NOT true about Aeromonas hydrophila?

Which statement is NOT true about Aeromonas hydrophila?

• A. Beta-hemolytic
• B. ONPG negative
• C. Catalase positive
• D. Oxidase positive

Answer: (B)

Aeromonas hydrophila typically shows a biochemical pattern that includes beta-hemolysis on blood agar, catalase positivity, and oxidase positivity, along with beta-galactosidase activity detected by the ONPG test. The ONPG test reveals whether an organism has beta-galactosidase; Aeromonas species usually produce this enzyme, so they yield a positive ONPG result. Therefore, the statement that it is negative for ONPG contradicts the common enzymatic profile of this organism. The other traits—beta-hemolysis, catalase positivity, and oxidase positivity—fit the expected phenotype and remain true.

Aeromonas hydrophila typically shows a biochemical pattern that includes beta-hemolysis on blood agar, catalase positivity, and oxidase positivity, along with beta-galactosidase activity detected by the ONPG test. The ONPG test reveals whether an organism has beta-galactosidase; Aeromonas species usually produce this enzyme, so they yield a positive ONPG result. Therefore, the statement that it is negative for ONPG contradicts the common enzymatic profile of this organism. The other traits—beta-hemolysis, catalase positivity, and oxidase positivity—fit the expected phenotype and remain true.