Legionella bacteria are aerobic, pleomorphic, gram negative bacilli found in fresh water environments and are usually transmitted through inhalation aerosols from contaminated water or soil. Legionnaire’s disease is a severe form of pneumonia caused by legionella species and can be community acquired or hospital acquired. The reported incidence of Legionnaires’ disease is approximately 1.4–1.8 cases per 100,000 persons and immunocompromised state is a very important risk factor. Some of the other important risk factors include old age, impaired cellular immunity, hematologic malignancies, solid organ transplantation, splenectomy, tumor necrosis factor-alpha inhibitors, chronic respiratory disease, diabetes and end stage renal disease. Legionella pneumophila serotype 1 is the most commonly reported cause of human Legionella infections. The pathogenesis of legionnaire’s disease involves invasion of alveolar macrophages and cell mediated immunity is the primary means of immune control. The prevalence of Legionnaires disease has risen possibly from increased awareness and reporting. The symptoms of the disease are nonspecific requiring a high index of suspicion in vulnerable hosts, as effective treatment could be life-saving. Sensitivity of urinary antigen testing is lower in immunocompromised patients because of higher likelihood of infections caused non L. pneumophila species. Extrapulmonary manifestations and higher mortality are particularly more common in immunocompromised patients than in immunocompetent hosts.
- legionnaires’ disease
- immunocompromised patients
- immunocompromised hosts
Legionnaire’s disease is a severe form of atypical pneumonia caused by gram-negative bacteria Legionella . Although Legionnaire’s disease is commonly reported in immunocompetent patients, immunocompromised state, particularly impaired cellular immunity is an independent risk factor for legionella infection. Diabetes, hematologic malignancies, chronic corticosteroid use, solid organ transplantation, TNF-alpha inhibitors are all risk factors for development of legionella infection .
2. Anti-Legionella immunity
Tumor necrosis factor alpha is vital in protecting the body from
3. Splenectomized patients
Legionella infection has not been frequently reported in splenectomized patients as these patients primarily have impairment in humoral immune response and B-lymphocyte function. A case report in 2004 reported two cases of Legionnaire’s disease in splenectomized patient. The first patient developed multiorgan failure and laboratory testing was positive for
4. Primary immunodeficiencies
Primary immunodeficiency disorder is the result of defective immune system development and the absence of functional immune system leads to severe infections. There has been only one case of legionella pneumonia reported in a patient with primary immunodeficiency disorder. It was a 35-year-old male with hyper IgE disease who presented with hemoptysis and was later diagnosed to have cavitary pneumonia due to legionella which was isolated from the BAL cultures and the patient also had a positive urinary legionella antigen .
5. Organ transplant patients
Although there are many species of Legionella,
A Spanish group of physicians retrospectively reviewed 287 cases of Legionnaires’ disease in solid organ transplant patients. They reported that 3% of the transplant recipients had contracted Legionnaires’ disease. Incidence of legionnaire’s disease was variable but higher in kidney, lung and heart transplant patients .
Extrapulmonary manifestations of
A group in Seattle, Washington reviewed 15 year longitudinal data in a hospital that cares for transplant patients and reported 32 cases of Legionnaires disease over a period of 15 years and 10 of them were in solid organ transplant patients .
6. Biologic agents
Biologic drugs are very commonly used for treatment of number of diseases and are associated with an increased risk of serious infections by lowering the immunity. A study done in France in 2006 over a period of 1 year revealed a case series of 10 patients treated with anti-TNF alpha therapy who were diagnosed with
Patients with hematological and solid tumors are at higher risk for developing legionnaire’s disease. A study found that Legionella caused 29% of pneumonia in patients with head and neck malignancies . A retrospective study over 4 years conducted in a oncology center in 1986 found 36 cases of Legionnaire’s disease. 42% had hematological malignancy and 22% had lung cancer. Neutropenic patients and patients on chronic steroids had higher risk of getting legionnaire’s disease .
Two retrospective studies were done at MD Anderson cancer hospital in Texas. First study reported 49 cases of Legionnaire’s disease in cancer patients over a period of 13 years from 1991 to 2003. The majority of patients had an underlying hematologic malignancy. 37% were bone marrow transplant recipients. Lymphopenia, use of corticosteroids and chemotherapy were the most common risk factors in these patients . Second retrospective study reviewed 33 consecutive cases of Legionnaire’s disease between 2002 and 2014. Out of this 27 had hematologic malignancies, 23 had neutropenia, 6 had allogeneic hematopoietic stem cell transplant and all patients except 1 had lung infection .
Clinical presentation of LD in immunocompromised patients:
Legionnaires disease in immunocompromised patients presents with fever, cough, chills, shortness of breath. GI symptoms can also occur. The incubation period for Legionnaires’ disease is usually around 2–10 days from the time of exposure to symptom onset. In immunocompromised patients in addition to consolidation legionnaire’s disease can present with cavitations, diffuse bilateral infiltrates and pleural effusions. In transplant patients nodular opacities that eventually cavitate have been reported . Pleural effusions have been reported in 15–50% of cases.
Pneumonia with cavitation has been reported in L pneumophila serotypes 1, 3, 4, 5, 6, and 8 as well as other Legionella species including
Extrapulmonary manifestations are usually seen in immunocompromised hosts . The incidence of Neurologic manifestations including meningoencephalitis, meningitis and transverse myelitis are similar to as in immunocompetent hosts. Cutaneous legionella has been reported in patients on chronic corticosteroids, solid organ transplants, stem cell transplants and hematological malignancies. They present with erythema, nodules, induration, ulcer or abscess. Most of them have concomitant lung infection .
Legionella can also affect the heart.
In conclusion while Legionella infection can occur in both immunocompetent and immunocompromised patients, certain risk factors in the immunocompromised are associated with an increased incidence. T cell and cell mediated immunity play a key role in body’s defense against the bacteria. TNF Alpha inhibitors are associated with an increased risk of Legionnaire’s disease. Extrapulmonary manifestations involving the skin, pericardium and aorta were seen more in immunocompromised, predominantly in patients on chronic corticosteroids, solid organ and stem cell transplant patients. The incidence of neurological manifestations remained the same. The signs and symptoms of Legionnaire’s disease are non-specific and patients with the above high risk features, especially on TNF alpha inhibitors should be screened for Legionella infection.