Recurrent soft tissue abscesses caused by Legionella cincinnatiensis

Recurrent soft tissue abscesses of the jaw, wrist, and arm developed in a 73-year-old housewife with nephrotic syndrome and immunoglobulin A(kappa) gammopathy of unknown etiology. Conventional cultures remained negative, despite visible gram-negative rods on microscopy. Broad-spectrum PCR revealed Legionella cincinnatiensis, which was confirmed by isolation of the organism on special Legionella medium. Infections due to Legionella species outside the lungs are rare. L. cincinnatiensis has been implicated in only four cases of clinical infection; these involved the lungs in three patients and the central nervous system in one patient. We conclude that broad-spectrum PCR can be a valuable tool for the evaluation of culture-negative infections with a high probability of bacterial origin and that Legionella might be an underdiagnosed cause of pyogenic soft tissue infection.