Antimicrobial stewardship challenges in extracorporeal membrane oxygenation

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.

Infection in ECMO patients: Changes in epidemiology, diagnosis and prevention

Patients with prolonged duration of extracorporeal membrane oxygenation support (ECMO) are a vulnerable population for sepsis, particularly ventilator-associated pneumonia and bloodstream infections. Rates differ between venous-arterial and venous-venous ECMO patients and according to the cannulation technique used. The presence of particular organisms depends on local epidemiology, antibiotic exposure, and the duration of the intervention; patients undergoing ECMO for more than three weeks present a high risk of persistent candidemia. Recognizing predisposing factors, and establishing the best preventive interventions and therapeutic choices are critical to optimizing the management of these complications. Infection control practices, including shortening the period of the indwelling devices, and reducing antibiotic exposure, must be followed meticulously. Innovations in oxygenator membranes require an updated approach. Hand hygiene and avoiding breaking the circuit-oxygenator sterility are cornerstones. ECMO management would benefit from clearer definitions, optimization of infection control strategies, and updated infectious clinical practice guidelines.