Legionnaires Disease in Solid Organ Transplant Recipients: A Decade-Long Nationwide Study in France

BACKGROUND

Legionnaires disease (LD) is a rare, life-threatening opportunistic bacterial infection that poses a significant risk to patients with impaired cell-mediated immunity such as solid organ transplant recipients. However, the epidemiologic features, clinical presentation, and outcomes of LD in this population are poorly described.

RESEARCH QUESTION

What are the clinical manifestations, radiologic presentation, risk factors for severity, treatment, and outcome of LD in solid organ transplant recipients?

STUDY DESIGN AND METHODS

In this 10-year multicenter retrospective cohort study in France, where LD notification is mandatory, patients were identified by hospital discharge databases. Diagnosis of LD relied on positive culture findings from any respiratory sample, positive urinary antigen test (UAT) results, positive specific serologic findings, or a combination thereof. Severe LD was defined as admission to the ICU.

RESULTS

One hundred one patients from 51 transplantation centers were eligible; 64 patients (63.4%) were kidney transplant recipients. Median time between transplantation and LD was 5.6 years (interquartile range, 1.5-12 years). UAT results were positive in 92% of patients (89/97). Among 31 patients with positive culture findings in respiratory samples, Legionella pneumophila serogroup 1 was identified in 90%. Chest CT imaging showed alveolar consolidation in 98% of patients (54 of 57), ground-glass opacity in 63% of patients (36 of 57), macronodules in 21% of patients (12 of 57), and cavitation in 8.8% of patients (5 of 57). Fifty-seven patients (56%) were hospitalized in the ICU. In multivariate analysis, severe LD was associated with negative UAT findings at presentation (P = .047), lymphopenia (P = .014), respiratory symptoms (P = .010), and pleural effusion (P = .039). The 30-day and 12-month mortality rates were 8% (8 of 101) and 20% (19 of 97), respectively. In multivariate analysis, diabetes mellitus was the only factor associated with 12-month mortality (hazard ratio, 3.2; 95% OR, 1.19-8.64; P = .022).

INTERPRETATION

LD is a late and severe complication occurring in solid organ transplant recipients that may present as pulmonary nodules on which diabetes impacts its long-term prognosis.

Legionella pneumophila Infections during a 7-Year Retrospective Analysis (2016-2022): Epidemiological, Clinical Features and Outcomes in Patients with Legionnaires' Disease

Legionella pneumophila (LP) is one of the main causative agents of community-acquired pneumonia in Europe and its fifth bacterial cause in Italy (4.9%). We conducted a seven year retrospective analysis of LP infection serogroup 1 in Asti, Piedmont, between 2016 and 2022. Patients were included if they tested positive for the Legionella urinary antigen. Clinical, laboratory, and radiologic data were analyzed to describe the risk factors for mortality. Fifty patients with LD were collected, mainly male, with a median age of 69 years. The main comorbidities were cardiovascular diseases (50%), pulmonary diseases (26%), and neurological diseases (12%). The most common clinical presentations were fever, respiratory, gastrointestinal, and neurologic symptoms. Older age (p = 0.004), underlying cardiovascular diseases (p = 0.009), late diagnosis at admission (p = 0.035), and neurological symptoms at diagnosis (p = 0.046) were more common in the non-survivor group. Moreover, a septic-shock presentation or the need for non-invasive ventilation at admission were associated with a higher mortality. No considerable differences in the biochemical data were found between the two groups except for the median neutrophil count, lymphocyte count, neutrophil-to-lymphocyte ratio, and PCT value. We did not find any differences in mortality related to the choice of antibiotic regimen. Differences in outcome were associated with the median duration of treatment (p =< 0.001) but not to the choice of antibiotic regimen (mainly levofloxacin or azithromycin). In conclusion, early individuation of the wide spectrum of clinical characteristics of LP infection such as respiratory, cardiac, and neurological manifestations of the patient's comorbidities, and significant biochemical data should help clinicians flag high risk patients and potentially improve their outcome.

How safe are gloves and masks used for protection against Legionella longbeachae infection when gardening?

Legionella longbeachae has been frequently identified in composted plant material and can cause Legionnaires' disease (LD). We wanted to determine how frequently L. longbeachae DNA was present on gardeners' gloves, and how long L. longbeachae could persist on inoculated gloves and masks. Volunteers completed a survey of gardening practices and their gardening gloves were tested for L. longbeachae DNA by qPCR. The persistence of viable L. longbeachae was assessed by timed subcultures after inoculation of gardening gloves and masks. Gloves but not masks were used regularly. L. longbeachae was detected on 11 (14%; 95% CI 8-24%) gloves. Viable organisms were recovered from 25-50% of inoculated cotton, leather and PU coated gloves but not rubber gloves after 8 h incubation. There was a difference in dose-response curve slopes by glove material (P = 0·001) and time to 50% sterility (P = 0·036). There were differences in persistence of L. longbeachae between mask types from analysis of the slopes and 50% sterility on the decay curves (P = 0·042, P < 0·001 respectively). Gardening gloves and masks may act as a vector for transmission of L. longbeachae during gardening. Washing gardening gloves and prompt disposal of masks could reduce risk of LD.

Hospital-acquired Legionella pneumonia outbreak at an academic medical center: Lessons learned

BACKGROUND

An outbreak of Legionella pneumonia occurred at a university hospital using copper-silver ionization for potable water disinfection. We present the epidemiological and laboratory investigation of the outbreak, and associated case-control study.

METHODS

Cases were defined by syndrome compatible with Legionella pneumonia with laboratory-confirmed Legionella infection. The water circuit and disinfection system were assessed, and water samples collected for Legionella culture. Whole genome multi-locus sequence typing (wgMLST) was used to compare the genetic similarity of patient and environmental isolates. A case-control study was conducted to identify risk factors for Legionella pneumonia.

RESULTS

We identified 13 cases of hospital-acquired Legionella. wgMLST revealed >99.9% shared allele content among strains isolated from clinical and water samples. Smoking (P= .008), steroid use (P= .007), and documented shower during hospitalization (P= .03) were risk factors for Legionella pneumonia on multivariable analysis. Environmental assessment identified modifications to the hospital water system had occurred in the month preceding the outbreak. Multiple mitigation efforts and application of point of use water filters stopped the outbreak.

CONCLUSIONS

Potable water system Legionella colonization occurs despite existing copper-silver ionization systems, particularly after structural disruptions. Multidisciplinary collaboration and direct monitoring for Legionella are important for outbreak prevention. Showering is a modifiable risk factor for nosocomial Legionella pneumonia. Shower restriction and point-of-use filters merit consideration during an outbreak.

Isolation and identification of Legionella spp. from hot spring water in Algeria by culture and molecular methods

AIMS

Due to infectious risk associated with the presence of Legionella in warm water, we determined the prevalence of living Legionella spp. in hot spring water in Algeria.

METHODS AND RESULTS

Detection of Legionella by culture was done by using two methods, direct culture on agar plates and co-culture with amoeba. Fifty samples were taken from different hot springs in northern Algeria, including swimming pools, showers and thermal sources. Legionella pneumophila serotypes were predominant, accounting for 60% of positive samples. Direct method allowed the isolation of 13 L. pneumophila only of 50 samples (26%), whereas co-culture using a panel of three free living amoeba allowed the isolation of 119 Legionella species from the same samples (80%) CONCLUSIONS: Amoeba co-culture allowed the isolation of several Legionella sp., while direct culture allowed the isolation of L. pneumophila only. Remarkably, Legionella longbeachae, usually isolated from soil and compost, was isolated for the first time in thermal water in three samples using Vermamoeba vermiformis co-culture.

SIGNIFICANCE AND IMPACT OF THE STUDY

The presence of Legionella in the water of hot springs in Algeria, which are mainly frequented by individuals at risk of Legionellosis, requires urgent control measures.

Legionella Persistence in Manufactured Water Systems: Pasteurization Potentially Selecting for Thermal Tolerance

Legionella is an opportunistic waterborne pathogen of increasing public health significance. Pasteurization, otherwise known as super-heat and flush (increasing water temperature to above 70°C and flushing all outlets), has been identified as an important mechanism for the disinfection of Legionella in manufactured water systems. However, several studies have reported that this procedure was ineffective at remediating water distribution systems as Legionella was able to maintain long term persistent contamination. Up to 25% of L. pneumophila cells survived heat treatment of 70°C, but all of these were in a viable but non-culturable state. This demonstrates the limitations of the culture method of Legionella detection currently used to evaluate disinfection protocols. In addition, it has been demonstrated that pasteurization and nutrient starvation can select for thermal tolerant strains, where L. pneumophila was consistently identified as having greater thermal tolerance compared to other Legionella species. This review demonstrates that further research is needed to investigate the effectiveness of pasteurization as a disinfection method. In particular, it focuses on the potential for pasteurization to select for thermal tolerant L. pneumophila strains which, as the primary causative agent of Legionnaires disease, have greater public health significance compared to other Legionella species.

The regulation of acute immune responses to the bacterial lung pathogen Legionella pneumophila

Legionella pneumophila causes Legionnaires' disease, a severe and potentially fatal bacterial pneumonia in immunocompromised individuals. Despite the understanding that a robust inflammatory response is important for control of L. pneumophila infection, our understanding of the network of molecular and cellular events within the lung that function to clear the bacterium is not clearly understood. This review compiles our understanding of the various molecular and cellular pathways stimulated upon infection with L. pneumophila and considers recently published advances that focus on the immune response to L. pneumophila in the lungs of mice. This includes a cooperative network of tissue-resident and inflammatory phagocytes, including alveolar macrophages (AM)s, neutrophils, and inflammatory monocytes/monocyte-derived cells (MC) that contribute to the acute inflammatory response and restrict the bacteria via distinct intracellular pathways. The understanding of this difference in cellular activity in response to infection provides insight into the innate immune responses within the tissues in general and may prompt novel means of clinical management of bacterial infections in an era of increasing emergence of antibiotic resistance.

Legionella Risk Management and Control in Potable Water Systems: Argument for the Abolishment of Routine Testing

Legionella is an opportunistic pathogen of public health significance. One of the main sources of Legionella is potable water systems. As a consequence of aging populations there is an increasing demographic considered at high risk for Legionellosis and, as such, a review of the guidelines is required. Worldwide, Legionella has been detected from many potable water sources, suggesting it is ubiquitous in this environment. Previous studies have identified the limitations of the current standard method for Legionella detection and the high possibility of it returning both false negative and false positive results. There is also huge variability in Legionella test results for the same water sample when conducted at different laboratories. However, many guidelines still recommend the testing of water systems. This commentary argues for the removal of routine Legionella monitoring from all water distribution guidelines. This procedure is financially consuming and false negatives may result in managers being over-confident with a system or a control mechanism. Instead, the presence of the pathogen should be assumed and focus spent on managing appropriate control measures and protecting high-risk population groups.

Epidemiologic characteristics associated with ST23 clones compared to ST1 and ST47 clones of Legionnaires disease cases in France

In France, approximately 1200 cases of Legionnaires disease (LD) are reported annually, and isolates are available for approximately 20% of cases identified since 2000. All Legionella pneumophila serogroup 1 (sg1) isolates are characterized by sequence-based typing at the National Reference Centre. LD cases caused by L. pneumophila sg1 reported from 2008 through 2012 were considered for the study. Our study objective was to describe cases according to their sequence type (ST). We also constructed multivariable modified Poisson regression models to estimate the incidence rate ratio (IRR) and to identify characteristics potentially associated with ST23 clones compared to ST1 and ST47 clones. We studied 1192 patients infected by ST1 (n = 109), ST23 (n = 236), ST47 (n = 123) or other STs (n = 724). The geographic distribution of the ST23 cases across the country was significantly different compared to other ST groups. This genotype was significantly associated with the absence of corticosteroid therapy compared to ST1 (IRR = 0.56; p 0.016). Concerning exposure, the ST23 genotype was significantly less associated with hospital-acquired infections compared to ST1 (IRR = 0.32; p 0.001), but it was more associated with infections acquired in hospitals and elderly settings compared with ST47. Finally, the ST23 genotype was less frequently associated with travel than other STs. Despite the large number of cases of ST23 infection, we did not identify any characteristics specific to this ST. However, we identified independent associations between ST1 and nosocomial transmission and steroid therapy. These findings should encourage further exploration, especially in terms of environmental diffusion, strain virulence and host factors.