Microbiological and Clinical Studies of Legionellosis in 33 Patients with Cancer

Abstract

Legionella, a large group of environmental Gram-negative bacteria, represents an occasional cause of pneumonia. We analyzed the microbiological and clinical features of 33 consecutive cases ofLegionellainfections that occurred at the University of Texas MD Anderson Cancer Center, Houston, TX, from 2002 to 2014. TheLegionellastrains were isolated from bronchoscopy specimens (32 strains) and a blood culture (1 strain) and were identified by sequencing analysis of the full-length 16S rRNA gene. The 33 strains involved 12Legionellaspecies or subspecies: 15 strains ofL. pneumophilasubsp.pneumophila, 3 strains ofL. pneumophilasubsp.fraseriorL. pneumophilasubsp.pascullei, 4 strains of “L. donaldsonii,” 3 strains ofL. micdadei, and one each ofL. bozemanae,L. feeleii,L. gormanii,L. longbeachae,L. maceachernii,L. parisiensis,L. sainthelensi, andLegionellasp. strain D5382. All patients except one asymptomatic carrier showed pneumonia, including one with concurrent bacteremia. Nine patients died, with this infection being the immediate cause of death in six. Twenty-seven patients had underlying hematologic malignancies. Twenty-three patients were leukopenic. Six patients were recipients of allogeneic hematopoietic stem cell transplant, with their infections caused by fiveLegionellaspecies. Together, these results suggest that diverseLegionellaspecies infect patients with cancer in the Houston area and its vicinity. The five cases of pneumonia due toL. donaldsoniiandLegionellasp. D5382 are likely the first reports of human infection with these organisms.