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Pneumonia and pulmonary abscess due to Legionella micdadei in an immunocompromised patient
Maud Foissac1, Ludovic Bergon2, Johanna Vidal3
1MD, Service de Maladies infectieuses, Centre Hospitalier Castres-Mazamet, 6 avenue de la Montagne Noire, 81100 Castres, France.
Introduction:
Legionella micdadei are gram-negative bacilli living in soil and aquatic habitats. They are responsible for less than 10% of legionellosis, but have a propensity to affect people suffering from immunodeficiency. Lung cavitations may also occur in this population. Isolation of L. micdadei on clinical samples requires specific culture media that are not routinely used. Moreover, serologic methods and urinary assays are specific for Legionella pneumophila serogroup 1 (the most frequent serogroup isolated from clinical specimens), and lack sensitivity for diagnosing L. micdadei infection. As a consequence, this diagnosis is difficult to confirm.
Case Report:
We report here a severe case of community-acquired legionellosis due to L. micdadei, in a patient under immunosuppressive medications and high-dose corticosteroids for rheumatoid arthritis. The source of his infection was hypothesized to be his continuous positive airway pressure device, which was regularly cleaned with tap water instead of sterile water, thus potentially resulting in Legionella contamination.
Conclusions:
L. micdadei must be considered as a possible cause of community-acquired severe pneumonia in case of immunodeficiency. For outpatients, advice concerning the cleaning of aerosols-generating devices at home must be emphasized.
Insights
Legionella micdadei causes severe pneumonia, especially in immunocompromised patients. Proper cleaning of home respiratory devices is crucial to prevent infection from contaminated tap water.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Pulmonology
Background:
- Legionella micdadei, a gram-negative bacillus found in aquatic environments, causes less than 10% of legionellosis cases.
- Immunocompromised individuals are particularly susceptible to L. micdadei infections, which can manifest as severe pneumonia with lung cavitation.
- Current diagnostic methods, including specific culture media, serologic tests, and urinary assays, are often inadequate for confirming L. micdadei infections.
Observation:
- A severe case of community-acquired legionellosis caused by L. micdadei is presented in a patient with rheumatoid arthritis on immunosuppressive therapy.
- The patient's continuous positive airway pressure (CPAP) device, cleaned with tap water, was hypothesized as the source of Legionella contamination.
- This case highlights the potential for household devices to harbor and transmit Legionella species.
Findings:
- L. micdadei should be considered in the differential diagnosis of severe community-acquired pneumonia, particularly in immunocompromised patients.
- The study underscores the diagnostic challenges associated with L. micdadei due to limitations in routine laboratory detection methods.
- Immunosuppression significantly increases the risk and severity of L. micdadei pneumonia.
Implications:
- Healthcare providers should maintain a high index of suspicion for L. micdadei in at-risk populations presenting with pneumonia.
- Public health recommendations should emphasize the importance of using sterile water for cleaning home aerosol-generating devices, such as CPAP machines.
- Further research into improved diagnostic tools for L. micdadei infections is warranted to facilitate timely and accurate diagnosis.
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