Blood cultures are recommended for recovery of which organism?

• A. Acinetobacter baumannii-calcoaceticus complex
• B. Brucella canis
• C. Chlamydia trachomatis
• D. Yersinia enterocolitica

Answer: (B)

Blood cultures are most informative when the organism causes bacteremia during systemic illness. Brucella species, including Brucella canis, typically circulate in the blood during active infection, so recovering the organism from blood is a key diagnostic approach. These bacteria are intracellular and slow-growing, so blood culture remains the most reliable method to confirm brucellosis, despite requiring extended incubation and careful biosafety handling.

In contrast, Chlamydia trachomatis is not diagnosed by blood culture; it is detected with nucleic acid amplification tests from mucosal specimens. Acinetobacter can cause bloodstream infections and be recovered from blood, but it is not the classic organism for which blood culture is the primary diagnostic test in this context. Yersinia enterocolitica can be found in blood in rare cases but is typically diagnosed from stool or tissue samples.