Case report: fatal pneumonia caused by new sequence type Legionella pneumophilia serogroup 1.

introductionLegionnaires' disease is caused by Legionella bacteria, and commonly manifests as pneumonia and has a high fatality rate. PATIENT CONCERNS: This case study reports on the fatal incident of a patient, initially diagnosed with pneumonia, and subsequently diagnosed with Legionnaires' disease caused by a new sequence type (ST) of Legionella. DIAGNOSIS: It is speculated that the patient acquired Legionnaires' disease from a contaminated water source. Legionnaires' disease was diagnosed using the Legionella urinary antigen assay and bacterial cultures of respiratory secretions; Legionella pneumophilia Type 1 was also identified through serological testing. Sequence-based typing of the cultured bacterium revealed it to be a previously unidentified species, and it was named ST2345 new-type.

interventionsIn addition to the treatment of Legionnaires' disease, blood samples taken on the second day of admission showed a co-infection of Candida tropicalis, which was treated with anti-fungal treatment. The patient improved after a week, however, on the seventh day of administration lower respiratory secretions showed the growth of Klebsiella pneumonia, indicative of ventilator-associated pneumonia. OUTCOMES: Despite active treatment, the patient passed away due to multiple organ failure. As this was a fatal case, further research is needed to determine whether the critical condition of this case was related to the virulence of the novel Legionella strain.

conclusionA key finding of this study is that treatment for suspected Legionnaires' disease must be administered rapidly, as infection with Legionella may give rise to secondary pathogenic infections.