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

INTRODUCTION: Legionnaires' 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. INTERVENTIONS: In 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. CONCLUSION: A 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.

[The clinical value of urinary antigen detection of Legionella pneumonia].

OBJECTIVE: To investigate the clinical value of urinary antigen detection of Legionella, and to describe the clinical characteristics of Legionella pneumonia. METHODS: Patients with suspected Legionella pneumonia were enrolled from the Respiratory departments of 3 tertiary hospitals in Shenyang during May 2011 to November 2013. Urinary Legionella antigen was detected for all the enrolled patients. Bacterial culture, polymerase chain reaction (PCR) for Legionella, and double Legionella antibody detection in sera were performed for each patient whose urinary antigen was positive. Patients confirmed to have Legionella pneumonia were pooled and analyzed. RESULTS: Totally 13 cases presenting with pneumonia were positive for Legionella by the urinary antigen method, and in one of them Legionella strain was isolated from the secretion of lower respiratory tract. PCR detection was performed in 8 patients, and 4 of them were positive. Legionella antibody detection was performed in 12 patients, and 7 of them were positive. Nine patients had a history of exposure to Legionella high-risk environments. The characteristics of the cases with Legionella pneumonia were as follows: characteristic orange sputum in 4 patients, digestive symptoms in 6, neurologic disorders in 8, hyponatremia in 10, hypoxia with oxygenation index < 300 mmHg (1 mmHg = 0.133 kPa) in 11, and severe pneumonia with PSI of grade V (PSI score > 130) in 8 patients . Chest CT scan showed bilateral involvement in 6, ground-glass opacity combined with consolidation in 11, and moderate pleural effusion in 11 patients. Cavity and reversed halo sign were found in one case, respectively. All of the patients received fluoroquinolone treatment, and 11 patients recovered completely while 2 died of multiple organ dysfunction syndrome, one of them was complicated with secondary infection. CONCLUSION: Detection of urinary antigen of Legionella is very useful in the diagnosis of Legionella pneumonia. Attention should be paid to exposure history to the high-risk environments and multiple organ impairment when Legionella infection is suspected. Orange sputum may be characteristic for Legionella pneumonia and therefore a clue for diagnosis. In critical cases, secondary infection and additional lung injuries induced by high concentration oxygen therapy may occur.