Antimicrobial Therapy for Legionnaire’s Disease

Severe Legionnaires' disease

BACKGROUND

Legionnaires' disease (LD) is a common but under-diagnosed cause of community-acquired pneumonia (CAP), although rapid detection of urine antigen testing (UAT) and advances in molecular testing have improved the diagnosis. LD entails intensive care unit (ICU) admission in almost one-third of cases, and the mortality rate ranges from 4% to 40%. This review aims to discuss recent advances in the study of this condition and to provide an update on the diagnosis, pathogenesis and management of severe LD.

RESULTS

The overall incidence of LD has increased worldwide in recent years due to the higher number of patients with risk factors, especially immunosuppression, and to improvements in diagnostic methods. Although LD is responsible for only around 5% of all-cause CAP, it is one of the three most common causes of CAP requiring ICU admission. Mortality in ICU patients, immunocompromised patients or patients with a nosocomial source of LD can reach 40% despite appropriate antimicrobial therapy. Regarding pathogenesis, no Legionella-specific virulence factors have been associated with severity; however, recent reports have found high pulmonary Legionella DNA loads, and impairments in immune response and lung microbiome in the most severe cases. The clinical picture includes severe lung injury requiring respiratory and/or hemodynamic support, extrapulmonary symptoms and non-specific laboratory findings. LD diagnostic methods have improved due to the broad use of UAT and the development of molecular methods allowing the detection of all Lp serogroups. Therapy is currently based on macrolides, quinolones, or a combination of the two, with prolonged treatment in severe cases.

CONCLUSIONS

Numerous factors influence the mortality rate of LD, such as ICU admission, the underlying immune status, and the nosocomial source of the infection. The host immune response (hyperinflammation and/or immunoparalysis) may also be associated with increased severity. Given that the incidence of LD is rising, studies on specific biomarkers of severity may be of great interest. Further assessments comparing different regimens and/or evaluating host-directed therapies are nowadays needed.

A 38-Year-Old Man With Persistent Fever and Progressive Shortness of Breath

CASE PRESENTATION

A 38-year-old man presented to the ED complaining of persistent fever, dry cough, shortness of breath, and diarrhea for 7 days. He reported a history of OSA with inconsistent CPAP use, tobacco use of less than one pack per day, and daily e-cigarette use or "vaping." He denied any contact with ill people or recent travels and was up to date on recommended COVID-19 vaccinations. Prior to his presentation, he had been seen at an urgent care facility twice in the last week, where he was given IV fluids and prescribed steroids without improvement.

Legionella: An uncommon cause of community-acquired pneumonia

ABSTRACT

Legionnaires disease is an important, relatively uncommon, yet well known form of atypical community-acquired pneumonia (CAP). If not appropriately treated in the early stage of infection, it can be fatal. Several factors increase the risk of contracting Legionnaires disease, including age over 50 years, chronic cardiovascular disease, underlying respiratory disease, chronic renal disease, diabetes, smoking, any immunosuppressing condition, travel history, and certain types of employment. Legionnaires disease can present without the usual symptoms associated with pneumonia. The incidence of Legionnaires disease is increasing, and because of its morbidity and mortality, clinicians should consider it in the differential when treating patients with CAP. This article reviews the pathophysiology and treatment of Legionnaires disease and when to refer patients to tertiary centers for higher levels of care, including extracorporeal membrane oxygenation.

Community acquired pneumonia by Legionella pneumophila: Study of 136 cases

OBJECTIVE

Most of the data on Legionella pneumonia in our country come from the Mediterranean area, and there are few studies from the Northwest area. This study tries to assess the situation of this infection in this area.

METHOD

Retrospective study of all patients with positive Legionella antigenuria treated at the University Hospital Lucus Augusti in Lugo (Spain) from 2001, the year in which this test was introduced in our centre, until 2015. We analysed epidemiological data, risk factors, clinical, radiological and biochemical findings, and clinical outcome.

RESULTS

The sampled included 136 patients. When comparing the first five years of the study with the last five, the incidence increased from 10.9 to 64.5 cases/1,000,000; the number of antigenuria requests increased 3.4 times, and compared to other pneumonia aetiologies Legionella increased from 0.9% to 15%. The mean age was 64.1years and 84.6% were males; 74.3% had comorbidities. Males were significantly younger (62.7±16.6 vs 71.9±17.3) and consumed more alcohol (26.1% vs 0%) and tobacco (67.8% vs 14.3%). Diagnosis was established within the first 72hours in 88.9% of cases and most received levofloxacin (95.6%). Hospitalisation was needed in 85% of cases, 11.7% in ICU and 4.4% died.

CONCLUSIONS

After the introduction of antigenuria there was an increase in the incidence of Legionella pneumonia recorded in our health area. Its rate in recent years has been one of the highest in our country. Despite the fact that the patients had advanced age and comorbidities, mortality was low.

Intrapulmonary Pharmacokinetics of Levonadifloxacin following Oral Administration of Alalevonadifloxacin to Healthy Adult Subjects

Alalevonadifloxacin (WCK 2349) is a novel l-alanine ester prodrug of levonadifloxacin that is being developed as an oral fluoroquinolone antibiotic. The primary objective of this study was to determine and compare plasma, epithelial lining fluid (ELF), and alveolar macrophage (AM) concentrations of levonadifloxacin following oral administration of alalevonadifloxacin to healthy adult subjects. Levonadifloxacin concentrations in plasma, ELF, and AM samples from 30 healthy subjects were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) following oral dosing of alalevonadifloxacin (1,000 mg twice daily for 5 days). Six subjects were assigned to each bronchoalveolar lavage (BAL) fluid sampling time, i.e., 2, 4, 6, 8, or 12 h after the ninth oral dose. Noncompartmental pharmacokinetic (PK) parameters were determined from serial total plasma concentrations collected over a 12-h interval following the first and ninth oral doses. Penetration ratios were calculated from the areas under the concentration-time curves from 0 to 12 h (AUC_0-12) for plasma, ELF, and AM by using mean (and median) concentrations at each BAL sampling time. Unbound plasma concentrations (∼85% plasma protein binding) were used to determine site-to-plasma penetration ratios. Plasma PK parameter values for levonadifloxacin were similar after the first and ninth doses. The respective AUC_0-12 values based on mean ELF and AM concentrations were 172.6 and 35.3 mg · h/liter, respectively. The penetration ratios for ELF and AM levonadifloxacin concentrations to unbound plasma levonadifloxacin concentrations were 7.66 and 1.58, respectively. Similar penetration ratios were observed with median concentrations. The observed plasma, ELF, and AM concentrations of levonadifloxacin support further studies of alalevonadifloxacin for treatment of lower respiratory tract bacterial infections caused by susceptible pathogens. (This study has been registered at ClinicalTrials.gov under identifier NCT02253342.).

Similarities and differences between doxycycline and minocycline: clinical and antimicrobial stewardship considerations

Doxycycline and, to a lesser extent, minocycline, have been used for decades to treat various serious systemic infections, but many physicians remain unfamiliar with their spectrum, interpretation of susceptibility results, pharmacokinetic/pharmacodynamic (PK/PD) properties, optimal dosing regimens, and their activity against MRSA, VRE, and multidrug-resistant (MDR) Gram-negative bacilli, e.g., Acinetobacter sp. This article reviews the optimal use of doxycycline and minocycline to treat a variety of infections and when minocycline is preferred instead of doxycycline.