Legionnaires\' disease is an atypical pneumonia caused by Legionella pneumophila. Legionella species are found in freshwater sources and are transmitted through inhalation of contaminated aerosols. Patients commonly present with fever, chills, and cough. However, in immunosuppressed patients or severe cases, the disease can lead to multiorgan failure. In recent years, the incidence of Legionnaires\' disease has drastically increased and unfortunately is commonly underdiagnosed. Gold-standard diagnosis is made through sputum cultures; however, urine Legionella antigen remains the most common test used for diagnosis. Goal-directed care includes antibiotics and supportive care. This case highlights a rare and unique presentation of Legionnaires\' disease presenting with an elevated 2:1 aspartate aminotransferase to alanine transaminase pattern, typically seen with alcoholic hepatitis.

Legionnaires\' disease is a potentially severe type of pneumonia most often caused by the organism Legionella pneumophila. Exposure to this bacterial pathogen typically happens in the community but may also occur in the hospital setting. This report describes the case of a patient who presented due to 10 days of fever, shortness of breath, and diarrhea, with initial imaging demonstrating multifocal pneumonia. The patient was appropriately started on empiric antibiotics for community-acquired pneumonia and admitted to the medicine floor. The patient showed no meaningful improvement in his initial hospital course on empiric antibiotics with continued oxygen requirements. Meanwhile, urine Legionella antigen testing returned positive on hospital day four, and after tailoring antibiotics accordingly, the patient\'s clinical status improved significantly. This case report highlights the efficacy of broad testing in the initial admission and the need for constant re-evaluation in the context of a patient not improving with appropriate therapy.

Legionella, one of the main pathogens that causes community-acquired pneumonia, can lead to Legionella pneumonia, a condition characterized predominantly by severe pneumonia. This disease, caused by the bacterium Legionella pneumophila, can quickly progress to critical pneumonia and is often associated with damage to multiple organs. As a result, it requires close attention in terms of clinical diagnosis and treatment. Omadacycline, a new type of tetracycline derivative belonging to the aminomethylcycline class of antibiotics, is a semi-synthetic compound derived from minocycline. Its key structural feature, the aminomethyl modification, allows omadacycline to overcome bacterial resistance and broadens its range of effectiveness against bacteria. Clinical studies have demonstrated that omadacycline is not metabolized in the body, and patients with hepatic and renal dysfunction do not need to adjust their dosage. This paper reports a case of successful treatment of Legionella pneumonia with omadacycline in a patient who initially did not respond to empirical treatment with moxifloxacin. The patient also experienced electrolyte disturbance, as well as dysfunction in the liver and kidneys, delirium, and other related psychiatric symptoms.

Many Legionella pneumonia patients do not produce sputum, and it is unknown whether purulent sputum is required for the identification of Legionella species. This study aimed to evaluate the identification rate of Legionella species based on sputum quality and the factors predictive of Legionella infection. This study included Legionella pneumonia patients at Kurashiki Central Hospital from November 2000 to December 2022. Sputum quality, based on gram staining, was classified as the following: Geckler 1/2, 3/6 and 4/5. Geckler 4/5 was defined as purulent sputum. The sputa of 104 of 124 Legionella pneumonia patients were cultured. Fifty-four patients (51.9%) were identified with Legionella species, most of which were Legionella pneumophila serogroup 1 (81.5%). The identification rates of Legionella species according to sputum quality were 57.1% (16/28) in Geckler 1/2 sputum, 50.0% (34/68) in Geckler 3/6 sputum, and 50.0% (4/8) in Geckler 4/5 sputum, which were not significantly different (P = 0.86). On multivariate analysis, pre-culture treatment with anti-Legionella antimicrobials (odds ratio [OR] 0.26, 95% confidence interval [CI] 0.06-0.91), Pneumonia Severity Index class ≥IV (OR 2.57 [95% CI 1.02-6.71]), and intensive care unit admission (OR 3.08, 95% CI 1.06-10.09) correlated with the ability to identify Legionella species, but sputum quality did not (OR 0.88, 95% CI 0.17-4.41). The identification rate of Legionella species in non-purulent sputum was similar to that in purulent sputum. For the diagnosis of Legionella pneumonia, sputum should be collected before administering anti-Legionella antibiotics and cultured regardless of sputum quality.

BACKGROUND: Legionella pneumonia, a severe form of pneumonia, is caused by Legionella bacteria. The epidemiology of Legionnaires\' disease in Japan, including seasonal trends, risk factors for severe disease, and fatality rates, is unclear. This study examined the epidemiology of Legionella pneumonia in Japan.
METHODS: This retrospective cohort study included data of adult patients hospitalized for Legionella pneumonia (identified using the ICD-10 code, A481) in the Japanese Diagnosis Procedure Combination inpatient database, from April 2011 to March 2021. We performed multivariable logistic regression analysis to explore the prognostic factors of in-hospital mortality.
RESULTS: Of 7370 enrolled hospitalized patients from 1140 hospitals (male, 84.4%; aged >50 years, 87.9%), 469 (6.4%) died during hospitalization. The number of hospitalized patients increased yearly, from 658 in 2016 to 975 in 2020. Multivariable logistic regression analysis revealed that higher in-hospital mortality was associated with older age, male sex, lower body mass index, worsened level of consciousness, comorbidities (congestive heart failure, chronic renal diseases, and metastasis), hospitalization from November to May, and ambulance use. However, lower in-hospital mortality was associated with comorbidity (liver diseases), hospitalization after 2013, and hospitalization in hospitals with higher case volume.
CONCLUSIONS: The characterized epidemiology of Legionella pneumonia in Japan revealed a high mortality rate of 6.4%. To the best of our knowledge, this is the first study to demonstrate a higher mortality rate in winter and in patients with congestive heart failure and metastasis. Further research is needed to understand the complex interplay between the prognostic factors of Legionella pneumonia.

The guidelines for the requirement of Legionella urinary antigen tests on admission for patients hospitalized with community-acquired pneumonia differ in Japan, the United States, and Europe. We aimed to evaluate the association between the timing of Legionella urinary antigen testing and inhospital mortality in patients with atypical pneumonia.
We identified 654,708 patients with atypical pneumonia from July 2010 to March 2021 using the Japanese national inpatient database. The patients were divided into groups that underwent Legionella urinary antigen tests on the day of admission (test group, n = 229,649) and those that underwent testing after the day of admission or were untested (control group, n = 425,059). A propensity score-stabilized inverse probability of treatment weighting analysis was performed to compare inhospital mortality, length of hospital stay, and total hospitalization costs between the two groups. Odds ratios (ORs) or differences and their 95% confidence intervals (CIs) were calculated using generalized linear models.
The tested group had a significantly lower 30-day inhospital mortality than that of the control group (7.7% vs. 9.0%; OR: 0.83 [95% CIs, 0.81-0.86]). The tested group also had a significantly shorter length of stay (difference, -2.3 [-2.6 to - 2.0] days and total hospitalization costs (-396 [-508 to - 285] US dollars) than that of the control group.
Legionella urinary antigen testing upon admission is associated with better outcomes in patients with atypical pneumonia. Legionella urinary antigen testing performed on the day of admission is recommended for hospitalized patients with atypical pneumonia.

OBJECTIVE: To analyze the differences in short- and long-term prognosis and the predictors of survival between patients with community-acquired Legionella and Streptococcus pneumoniae pneumonia, diagnosed early by urinary antigen testing (UAT).
METHODS: Prospective multicenter study conducted in immunocompetent patients hospitalized with community-acquired Legionella or pneumococcal pneumonia (L-CAP or P-CAP) between 2002-2020. All cases were diagnosed based on positive UAT.
RESULTS: We included 1452 patients, 260 with community-acquired Legionella pneumonia (L-CAP) and 1192 with community-acquired pneumococcal pneumonia (P-CAP). The 30-day mortality was higher for L-CAP (6.2%) than for P-CAP (5%). After discharge and during the median follow-up durations of 11.4 and 8.43 years, 32.4% and 47.9% of patients with L-CAP and P-CAP died, and 82.3% and 97.4% died earlier than expected, respectively. The independent risk factors for shorter long-term survival were age >65 years, chronic obstructive pulmonary disease, cardiac arrhythmia, and congestive heart failure in L-CAP and the same first three factors plus nursing home residence, cancer, diabetes mellitus, cerebrovascular disease, altered mental status, blood urea nitrogen ≥30 mg/dl, and congestive heart failure as a cardiac complication during hospitalization in P-CAP.
CONCLUSIONS: In patients diagnosed early by UAT, the long-term survival after L-CAP or P-CAP was shorter (particularly after P-CAP) than expected, and this shorter survival was mainly associated with age and comorbidities.

Objective Recommendations on the timing of Legionella urinary antigen tests for community-acquired pneumonia patients differ among guidelines in Japan, the United States, and European nations. We therefore evaluated the association between the timing of urinary antigen tests and in-hospital mortality in patients with Legionella pneumonia. Methods We conducted a retrospective cohort study using the Diagnosis Procedure Combination database, a nationwide database of acute care inpatients in Japan. Patients who underwent Legionella urinary antigen tests on the day of admission formed the tested group. Patients who were tested on day 2 of admission or later or were unexamined formed the control group. We performed a propensity score matching analysis to compare in-hospital mortality, length of hospital stay and duration of antibiotics use between the two groups. Results Of the 9,254 eligible patients, 6,933 were included in the tested group. One-to-one propensity score matching generated 1,945 pairs. The tested group had a significantly lower 30-day in-hospital mortality than the control group (5.7 vs. 7.7%; odds ratio, 0.72; 95% confidence intervals, 0.55-0.95; p=0.020). The tested group also showed a significantly shorter length of stay and duration of antibiotics use than the control group. Conclusion Urine antigen testing upon admission was associated with better outcomes in patients with Legionella pneumonia. Urine antigen tests upon admission may be recommended for all patients with severe community-acquired pneumonia.

Legionella pneumonia is a fatal disease caused by Legionella pneumophila, a bacterium belonging to the genus Legionella. The incidence of this disease has been increasing since 2005 and has continued to increase following the COVID-19 pandemic in Japan. Furthermore, Legionella pneumonia mortality rates have increased slightly since the pandemic due to some plausible reasons. The increased proportion of older patients with legionellosis might affect it because advanced age is a major risk factor for disease mortality. Additionally, physicians were focused on COVID-19 while examining febrile patients; therefore, they might have missed the early diagnosis of other respiratory infections, including Legionella pneumonia.

A 79-year-old man presented with chest pain, and urinary antigen tests for Legionella pneumophila (ImmunoCatch® Legionella and Ribotest® Legionella) were negative on admission. The next day, rapid respiratory failure suggested Legionella pneumonia, and levofloxacin was added. Since a lung infiltration shadow appeared on the other side as well on day 4, non-infectious diseases were considered, and steroid therapy was started. Urinary antigen tests for Legionella pneumophila became positive on day 5. In the present case, retesting with Ribotest® Legionella, which could be negative early after the disease onset, was useful for diagnosing Legionella pneumonia, which led to the discontinuation of unnecessary steroid treatment.