title: Legionella pneumophila serogroup 3 pneumonia in a patient with low-grade 4 non-Hodgkin lymphoma: a case report.
abstract: BACKGROUND
  Nosocomial legionellosis has generally been described in immunodepressed patients, but Legionella pneumophila serogroup 3 has rarely been identified as the causative agent.
  
  
  METHODS
  We report the case of nosocomial L. pneumophila serogroup 3 pneumonia in a 70-year-old Caucasian man with non-Hodgkin lymphoma. Diagnosis was carried out by culture and real-time polymerase chain reaction of bronchoalveolar lavage fluid. The results of a urinary antigen test were negative. A hospital environmental investigation revealed that the hospital water system was highly colonized by L. pneumophila serogroups 3, 4, and 8. The hospital team involved in the prevention of infections was informed, long-term control measures to reduce the environmental bacterial load were adopted, and clinical monitoring of legionellosis occurrence in high-risk patients was performed. No further cases of Legionella pneumonia have been observed so far.
  
  
  CONCLUSIONS
  In this report, we describe a case of legionellosis caused by L. pneumophila serogroup 3, which is not usually a causative agent of nosocomial infection. Our research confirms the importance of carrying out cultures of respiratory secretions to diagnose legionellosis and highlights the limited value of the urinary antigen test for hospital infections, especially in immunocompromised patients. It also indicates that, to reduce the bacterial load and prevent nosocomial legionellosis, appropriate control measures should be implemented with systematic monitoring of hospital water systems.
authors.affiliation: Department of Experimental Medicine and Biochemical Sciences, Microbiology Section, University of Perugia, Via del Giochetto, Perugia 06122, Italy. vecchiar@unipg.it.
authors.forename: Antonella
authors.initials: A
authors.lastname: Mencacci
authors.forename: Cristina
authors.initials: C
authors.lastname: Corbucci
authors.forename: Alessio
authors.initials: A
authors.lastname: Castellani
authors.forename: Paolo
authors.initials: P
authors.lastname: Furno
authors.forename: Francesco
authors.initials: F
authors.lastname: Bistoni
authors.forename: Anna
authors.initials: A
authors.lastname: Vecchiarelli