A Painful Swelling on the Chest

Abstract

Diagnosis: Thoracic actinomycosis. Gram stain of the purulent aspirate obtained from the mass protruding through the thoracic wall (figures 1 and 2) showed irregular gram-positive rods without branching, as well as gram-negative rods (figure 3). Aerobic and anaerobic cultures yielded 3 bacterial strains. The first-an anaerobic, slow-growing, catalase-negative gram-positive rod-was identified as Actinomyces israelii by 16S RNA gene sequencing. The second strain was another anaerobic, very slow-growing, slender gramnegative rod with pointed ends, identified by 16S RNA gene sequencing as Fusobacterium nucleatum. The third microorganism that was isolated was a fastidious, catalase-positive gram-negative rod that was identified as Actinobacillus actinomycetemcomitans.