Gram-positive rods were recovered from the chest fluid of a teenager with pneumonia; CAMP test positive and catalase negative. The most likely etiologic agent is?

Gram-positive rods were recovered from the chest fluid of a teenager with pneumonia; CAMP test positive and catalase negative. The most likely etiologic agent is?

• A. Listeria monocytogenes
• B. Streptococcus agalactiae
• C. Arcanobacterium pyogenes
• D. Streptobacillus moniliformis

Answer: (C)

CAMP test positivity with a gram-positive rod that is catalase negative points to Arcanobacterium species. The CAMP factor produced by these organisms enhances the hemolysis of Staphylococcus aureus on blood agar, giving a positive CAMP reaction. In this scenario, the isolate is a gram-positive rod and catalase negative, which fits Arcanobacterium pyogenes (Arcanobacterium haemolyticum) best. Other options either are not rods (Streptococcus agalactiae is a cocci), or are catalase-positive (Listeria monocytogenes), or are gram-negative (Streptobacillus moniliformis), so they don’t match the findings.

CAMP test positivity with a gram-positive rod that is catalase negative points to Arcanobacterium species. The CAMP factor produced by these organisms enhances the hemolysis of Staphylococcus aureus on blood agar, giving a positive CAMP reaction. In this scenario, the isolate is a gram-positive rod and catalase negative, which fits Arcanobacterium pyogenes (Arcanobacterium haemolyticum) best. Other options either are not rods (Streptococcus agalactiae is a cocci), or are catalase-positive (Listeria monocytogenes), or are gram-negative (Streptobacillus moniliformis), so they don’t match the findings.