Microbiological and Clinical Studies of Legionellosis in 33 Patients with Cancer.

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 of Legionella infections that occurred at the University of Texas MD Anderson Cancer Center, Houston, TX, from 2002 to 2014. The Legionella strains 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 12 Legionella species or subspecies: 15 strains of L. pneumophila subsp. pneumophila, 3 strains of L. pneumophila subsp. fraseri or L. pneumophila subsp. pascullei, 4 strains of "L. donaldsonii," 3 strains of L. micdadei, and one each of L. bozemanae, L. feeleii, L. gormanii, L. longbeachae, L. maceachernii, L. parisiensis, L. sainthelensi, and Legionella sp. 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 five Legionella species. Together, these results suggest that diverse Legionella species infect patients with cancer in the Houston area and its vicinity. The five cases of pneumonia due to L. donaldsonii and Legionella sp. D5382 are likely the first reports of human infection with these organisms.