Legionella pneumophila (L. pneumophila) is a gram-negative intracellular bacillus composed of sixteen different serogroups. It is mostly known to cause pneumonia in individuals with known risk factors as immunocompromised status, tobacco use, chronic organ failure or age older than 50 years. Although parapneumonic pleural effusion is frequent in legionellosis, pleural empyema is very uncommon. In this study, we report a case of fatal pleural empyema caused by L. pneumophila serogroup 1 in an 81-year-old man with multiple risk factors.

An 81-year-old man presented to the emergency with a 3 wk dyspnea, fever and left chest pain. His previous medical conditions were chronic lymphocytic leukemia, diabetes mellitus, chronic kidney failure, hypertension and hyperlipidemia, without tobacco use. Chest X-ray and comouted tomography-scan confirmed a large left pleural effusion, which puncture showed a citrine exudate with negative standard bacterial cultures. Despite intravenous cefotaxime antibiotherapy, patient’s worsening condition after 10 d led to thoracocentesis and evacuation of 2 liters of pus. The patient progressively developed severe hypoxemia and multiorgan failure occurred. The patient was treated by antibiotherapy with cefepime and amikacin and with adequate symptomatic shock treatment, but died of uncontrolled sepsis. The next day, cultures of the surgical pleural liquid samples yielded L. pneumophila serogroup 1, consistent with the diagnosis of pleural legionellosis.

L. pneumophila should be considered in patients with multiple risk factors and undiagnosed pleural empyema unresponsive to conventional antibiotherapy.

Legionella pneumophila (L. pneumophila) is a Gram-negative, slow-growing intracellular bacillus, originally discovered in 1976 in Philadelphia among the delegates of the American Legion conference[1]. Since then, sixteen different serogroups have been described, with a large predominance of serogroup 1, responsible for approximatively 85% of the cases[2]. Risk factors for infection include male sex, aged more than 50 years, current or historical smoking, alcohol abuse, diabetes, cancer, chronic kidney failure, iron overload and immunocompromising diseases or treatments[3]. Although it is mostly known to cause acute severe pneumonia, with frequent parapneumonic pleural effusion, L. pneumophila infection may rarely cause pleural empyema.

We report here a case of pleural empyema caused by L. pneumophila serogroup 1 in an immunocompromised patient, followed by a review of the literature.

Fatal pleural empyema caused by L.pneumophila serogroup 1.

No specific treatment could have been introduced because of post-mortem diagnosis. Unfortunately, the L. pneumophila stain identified in our patient was naturally resistant to all the antibiotics received.

Patient died of uncontrolled sepsis caused by L. pneumophila serogroup 1 pleural empyema.

Pleural effusion is a common manifestation of Legionnaire’s disease. In a case series of 36 microbiologically proven legionellosis, Sakai et al[4] reported in 2007 unilateral or bilateral scannographic pleural effusion in 60% of pneumonia caused by L. pneumophila, considered as a parapneumonic aseptic transudate. Similarly, Poirier et al[5] reported in 2017, in a 33 individuals canadian cohort, a scannographic frequency of 66% (22/33). In contrast, pleural empyema, defined as a septic exudate with presence of L. pneumophila, seems exceptional.

Prevalence of pleural empyema in legionellosis is largely unknown. Since 1979, only 11 cases have been reported. These cases involved mostly men with an age ranging between 36 and 83[6-12]. L. pneumophila serogroup 1 seems to be involved in most cases, but one serogroup 5 nosocomial L. pneumophila has been described in a patient following esophageal perforation after esophageal dilatation for carcinoma[6-8]. All infected patients with detailed history presented classic risk factors: Tobacco use, relative immunosuppression caused by advanced age, high-dose steroids as a treatment for systemic lupus erythematosus[9], immunosuppressive drugs in a kidney transplant recipient[10]. In 1981, Winn and Myerowitz reported two necropsias of fatal legionellosis with unilateral empyema with presence of L. pneumophila in pleural fluid[11]. Characteristics of pleural liquid, available for six cases, seem to be those of a classic empyema : Macroscopically purulent or serofibrinous, elevated LDH (5 out of 5, 1 non tested, range 342-2371 UI/L) and proteins (6 out of 6, range 31-57 g/L), with a predominance of neutrophils (6 out of 6) , with hypoglycopleuria and acid pH.

L. pneumophila infection is associated with a poor outcome: In a retrospective study of 136 consecutive cases of communautary L. pneumophila infection in Spain between 2001 and 2015, 85% of patients were hospitalized, including 11.7% in intensive care unit, and the mortality rate was 4.4%[13]. Of the 11 patients described, 2 died with unrecorded treatment, 7 patients survived with adequate antibiotic course, and the outcome of the 2 last was unknown. Choice of antibiotic stewardship and duration of antibiotic course for pleural legionellosis is widely empirical: 4 patients received a 4 wk course of IV erythromycin, 2 received a combination of erythromycin and rifampicin during 8 wk, and the last one was treated with levofloxacin for an undetermined duration of time.

Early identification of sepsis and early administration of adapted antibiotherapy is now recommended by international clinical practice guidelines[14]. In our case report, identification of sepsis and its pleural origin was easy. Unfortunately, empirical antibiotherapy did not cover Legionellosis, and probably led to the patient’s death.

Extrapulmonary legionellosis is a very challenging diagnosis and might involve many different organs[15-18]. In patients with immunocompromising conditions, L. pneumophila can cause septic arthritis, endocarditis, myocarditis, myositis or cutaneous involvement, including panniculitis, exanthema, subcutaneous nodules, pustules or even abscesses. Other Legionella species include, among others, L. bozemanii, and L. micdadei[2]. These other species, much rarer than L. pneumophila, can also exceptionally cause pneumonia with pleural empyema, which seems to be overrepresented compared to L. pneumophila[19,20]. Mycoplasma pneumonia, another intracellular bacteria known to cause pneumonia, has also been reported a few times as the causative agent of pleural empyema[21].

Although uncommon, pleural empyema caused by L. pneumophila is associated with a poor outcome, and is therefore a very challenging diagnosis. We suggest that Legionnaire’s disease should be considered in patients with multiple risk factors and pleural empyema with negative bacteriological standard culture and unresponsive to conventional antibiotherapy.

The authors would like to thank Laetita Beraud, from the French National Reference Center for Legionella, for her work in the identification of serogroup 1 Legionella pneumophila.