Current and Emerging Legionella Diagnostics for Laboratory and Outbreak Investigations

Abstract

SUMMARY Legionnaires' disease (LD) is an often severe and potentially fatal form of bacterial pneumonia caused by an extensive list of Legionella species. These ubiquitous freshwater and soil inhabitants cause human respiratory disease when amplified in man-made water or cooling systems and their aerosols expose a susceptible population. Treatment of sporadic cases and rapid control of LD outbreaks benefit from swift diagnosis in concert with discriminatory bacterial typing for immediate epidemiological responses. Traditional culture and serology were instrumental in describing disease incidence early in its history; currently, diagnosis of LD relies almost solely on the urinary antigen test, which captures only the dominant species and serogroup, Legionella pneumophila serogroup 1 (Lp1). This has created a diagnostic “blind spot” for LD caused by non-Lp1 strains. This review focuses on historic, current, and emerging technologies that hold promise for increasing LD diagnostic efficiency and detection rates as part of a coherent testing regimen. The importance of cooperation between epidemiologists and laboratorians for a rapid outbreak response is also illustrated in field investigations conducted by the CDC with state and local authorities. Finally, challenges facing health care professionals, building managers, and the public health community in combating LD are highlighted, and potential solutions are discussed.

Legionella Survey in the Plumbing System of a Sparse Academic Campus: A Case Study at the University of Perugia

“…Our data are largely in agreement with other works indicating that strains of L. pneumophila, the species mostly associated to legionellosis, are those mostly often found to contaminate taps of private apartments, hotels and hospitals in Italy [13] as well as buildings in Hungary, Germany, the USA and Japan [14][15][16]23]. Nevertheless, we also recovered several isolates of L. anisa, a species already found in building plumbing [14] and known to be associated with human infections as one of the pathogens causing Pontiac fever [1]; as well as one isolate identified as L. tauriniensis, a species recently isolated from a hospital humidifier in Turin, Italy [24] but never linked to human disease. Since several isolates were cultured from each water sample, all the sequences were aligned, and a representative one was chosen from each group of isolates obtained from the same control-point tap and identified as the same Legionella species.…”

“…Considering that several species of Legionella have been identified but only few of them have been associated with human disease [1], we used a molecular analysis based on mip gene sequencing to identify the Legionella species and to differentiate the serogroups of L. pneumophila within the strains retrieved from the University buildings' plumbing (Table 1 and Figure 4). …”

“…The occurrence of Legionella contaminations in a building's tap water represents a serious health threat to end-users since it may infect human lungs, causing a form of atypical pneumonia called legionellosis or Legionnaires' disease [1,2]. The last available report, related to 2015, shows that in Europe 30 countries reported more than 6500 confirmed cases of legionellosis, corresponding to an overall rate of 14 per million inhabitants, with an increase over the 2011-2015 period [3].…”

“…The genus Legionella comprises more than 50 different bacterial species and at least 18 of them have been associated with human disease [1,3]. It is generally supposed that more than 90% of …”

Vital Signs: Deficiencies in Environmental Control Identified in Outbreaks of Legionnaires’ Disease — North America, 2000–2014

“…Only one case of possible person-to-person transmission has been reported (8). Legionnaires' disease is typically diagnosed by a Legionella urinary antigen test or culture of lower respiratory secretions using selective media; epidemiologic links to environmental sources can be confirmed when isolates from clinical and environmental specimens match by molecular typing (9). One species, Legionella pneumophila, accounts for approximately 90% of reported legionellosis cases in the United States (7).…”