Legionnaires Disease with Bacteremic Coinfection

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Abstract
We describe 6 patients who had bacteremic community-acquired pneumonia and unsuspected Legionella pneumophila coinfection. We reviewed case records of patients who were diagnosed as having a recent Legionella infection on the basis of either the presence of L. pneumophila serogroup 1 antigen in urine or a 4-fold increase in L. pneumophila antibody level and with a blood culture that yielded a bacterium other than L. pneumophila. Three patients were diagnosed with legionellosis on the basis of the presence of antigen in urine, and 3 were diagnosed on the basis of a 4-fold increase in antibody titer. Of these 6 patients, 4 were infected with Streptococcus pneumoniae, 1 with Streptococcus pyogenes, and 1 with Enterobacter cloacae. L. pneumophila infection in these patients may have predisposed them to concomitant bacteremia. Initial empiric antimicrobial therapy for patients who live in areas of endemicity and who are smokers should be treated with antimicrobial agents that have activity against pneumococcus and Legionella species.