Comparison of Legionella longbeachae and Legionella pneumophila cases in Scotland; implications for diagnosis, treatment and public health response

Abstract

The reported incidence of Legionnaires' disease caused by Legionella longbeachae has increased since 2008 in Scotland. While microbiological and epidemiological studies have identified exposure to growing media as a risk factor for infection, little is known about the differences regarding disease risk factors, clinical features and outcomes of infection with L. longbeachae when compared with L. pneumophila. A nested case-case study was performed comparing 12 L. longbeachae cases with 25 confirmed L. pneumophila cases. Fewer L. longbeachae infected patients reported being smokers [27 % (95 % CI 2-52 %) vs. 68 % (95 % CI 50-86 %), P50.034] but more L. longbeachae patients experienced breathlessness [67 % (95 % CI 40-94 %) vs. 28 % (95 % CI 10-46 %), P50.036]. Significantly more L. longbeachae-infected patients received treatment in intensive care [50 % (95 % CI 22-78 %) vs. 12 % (95 % CI 0-25 %), P50.036]. However, the differences in diagnostic methods between the two groups may have led to only the most severe cases of L. longbeachae being captured by the surveillance system. No differences were observed in any of the other pre-hospital symptoms assessed. Our results highlight the similarity of Legionnaires' disease caused by L. pneumophila and L. longbeachae, and reinforce the importance of diagnostic tools other than the urinary antigen assays for the detection of non-L. pneumophila species. Unfortunately, cases of community-acquired pneumonia caused by Legionella species will continue to be underdiagnosed unless routine testing criteria changes.

Performance of Legiolert Test vs. ISO 11731 to Confirm Legionella pneumophila Contamination in Potable Water Samples

“…Therefore, many cases caused by other species might not be detected even by culture for this reason. Until a suitable medium for growing other Legionella species is developed, a routine PCR test in diagnosing human specimens, capable of distinguishing between Legionella pneumophila and other species, should be adopted in order to identify the real burden of Legionnaires' disease, as already demonstrated in a few countries [31][32][33][34][35][36][37]. The results of these studies will be able to confirm the real incidence of infections caused by other Legionella species and consequently to address the choices on what should be the focus of monitoring in the environment.…”

“…The imminent introduction of the new drinking water legislation concerning the monitoring of an increasing number of water systems, however, will probably lead to streamlined choices aimed at reducing health risk by researching the most pathogenic and prevalent species present in the environment. Despite this, it must still be considered that for specific countries where other species of Legionella, such as Legionella longbeachae, are the prevalent in specific non-water matrices such as compost, and are an increasing cause of LD cases, Legiolert should not be utilized [1,31,35,37].…”

Legionnaires' disease caused by Legionella longbeachae: Clinical features and outcomes of 107 cases from an endemic area

“…Although about one quarter of patients with both L. longbeachae and L. pneumophila pneumonia required ICU admission, the mortality (5%) was lower than for L. pneumophila (10%) and for Legionnaires' disease reported elsewhere (8–12%) . Interestingly, the mortality for both species was lower than those reported in our previous study of pneumonia (21–25%) and lower than that in a recent single centre study from Scotland (50%), but both studies only included culture‐diagnosed cases whom may have more severe disease. In our centre, non‐invasive ventilation is not routinely performed outside ICU, which may increase our ICU admission rate compared with other centres who perform this on wards.…”

Increase in Legionnaires’ disease cases associated with travel to Dubai among travellers from the United Kingdom, Sweden and the Netherlands, October 2016 to end August 2017

“…The LD surveillance systems in our countries have been described elsewhere [ 4 - 7 ]. In brief, LD must be notified by medical practitioners to public health authorities, who interview the patient or close family members to identify potential legionella exposures during the incubation period, including any travel away from the patient’s main residence (national and/or foreign travel).…”