Legionella and legionnaires' disease: An overview

Abstract

Legionellosis is the generic term used to describe infections caused by different varieties of Legionella spp., including Legionnaires’ disease (LD), a severe and potentially fatal form of pneumonia, and Pontiac fever, a self-limited flu-like illness. Legionellosis is usually acquired through inhalation or aspiration of aerosols containing Legionella spp. These bacteria can cause acute consolidating pneumonia in susceptible patients who are at an advanced age, have underlying debilitating diseases, or are immunodeficient. The main natural reservoir for Legionella is water and this pathogen colonizes many different natural and man-made freshwater environments such as water networks, cooling towers, and water systems in buildings and hospitals. In recent years, various laboratory diagnostic tests for Legionella infections have changed significantly. Although the sequencing method is nowadays considered the fastest and most reliable method for differentiation and detection of different Legionella species, the isolation of these bacteria from clinical specimens is the golden standard for diagnosis of Legionnaires’ disease. Today the urinary antigen test as the most rapid and inexpensive method is routinely used for diagnosis of LD caused by Legionella pneumophila serogroup 1. The macrolides and fluoroquinolones are still the mainstays for the treatment of Legionella infections. For the prevention of spreading the contaminated water aerosols and controlling Legionella infections, an effective water treatment procedure is necessary. This review describs and summarizes the latest available information about all aspects of Legionella and Legionnaires’ disease.