Identification of legionella in clinical samples

Legionella maceachernii pneumonia: a case report and literature review

BACKGROUND

Legionella maceachernii pneumonia is a severe respiratory infection with low incidence but high mortality. However, the optimal treatment for this disease remains unclear. We report a case of successful treatment of Legionella maceachernii pneumonia, which is the first report of such a case in China.

CASE PRESENTATION

An 87-year-old man with concomitant chronic obstructive pulmonary disease, liver cirrhosis, and history of left nephrectomy was diagnosed with Legionella maceachernii pneumonia using Dano-seq pathogen metagenomic testing. After two weeks of treatment with cefoperazone/sulbactam combined with quinolone antibiotics, the patient showed improvement and was discharged. The patient continued to take oral quinolone antibiotics for one week after discharge and recovered during outpatient follow-up.

CONCLUSIONS

Dano-seq pathogen metagenomic testing can rapidly diagnose Legionella maceachernii pneumonia, and taking quinolone antibiotics is an effective treatment.

Legionella-Induced Rhabdomyolysis and Acute Kidney Injury: A Case Report

Legionella pneumonia is a severe form of pneumonia caused by the bacterium Legionella pneumophila. It often presents with atypical symptoms and can lead to complications such as rhabdomyolysis and acute kidney injury (AKI). Here, we report a case of Legionella pneumonia-induced rhabdomyolysis and AKI in a 32-year-old male. Laboratory investigations revealed elevated creatinine kinase levels and acute kidney injury. Further investigation confirmed Legionella pneumonia. The patient was promptly treated with appropriate antibiotics and supportive care, resulting in clinical improvement and resolution of rhabdomyolysis and AKI. This case underscores the importance of considering Legionella pneumonia as a potential cause of rhabdomyolysis and AKI, especially in patients with atypical pneumonia presentations.

[Legionnaires' disease in Argentina: Evolution of the laboratory diagnostic strategy]

Legionnaires' disease (LD) is severe acute pneumonia that occurs in sporadic or epidemic form, and generally requires hospitalization. The objective of this work was to describe the experience in the LD laboratory diagnostic approach in Argentina during the period 2016-2021. The laboratory analyzed 168 clinical specimens from 93 cases of suspected LD pneumonia. Laboratory tests included the detection of the soluble antigen of Legionella pneumophila serogroup 1 in urine sample, detection of DNA of Legionella spp. in lower respiratory secretions by conventional and commercial molecular methods and isolation in selective medium. LD was confirmed in 12 patients. The urinary antigen allowed the diagnosis for 8 patients. L. pneumophila was isolated from the respiratory material of 6 patients suffering from health care-associated pneumonia, who had been previously diagnosed using the commercial molecular method. Fifty percent of these cases did not show detectable urinary antigen. A single patient did not shows neither detectable antigenuria nor isolation of Legionella from the respiratory sample and was diagnosed as a confirmed case of LD by the detection of DNA of Legionella spp. by PCR directly from the respiratory secretion and the epidemiological link with another case of confirmed LD by culture. Urinary antigen detection is the first-line diagnostic test. However, the incorporation of complementary molecular methods has proved to avoid false negatives and contributed to a better understanding of the true incidence of the disease.

Strain-Level Characterization of Legionella Environmental Isolates via MALDI-TOF-MS

As a waterborne pathogen of increasing concern, techniques for cost-effective and rapid characterization of Legionella are vital. This study examines the development of a Matrix Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-TOF-MS) analysis methodology for this microbe. First, optimal sample preparation methods for the analysis of environmental Legionella isolates via MALDI-TOF-MS were determined. These methods were then implemented to perform strain-level characterization of environmental Legionella isolates from central Arizona. Results demonstrate that a MALDI-TOF-MS method involving BCYE agar-based culturing and protein extraction-based sample preparation yield high-quality mass spectra. Twenty-eight environmental Legionella isolates originating from two separate drinking water distribution systems were analyzed. Multiple species were detected, and strain-level characterization was achieved, with 12 unique strains distinguished. In addition, isolates of L. pneumophila, the most common species observed in the study, were correctly assigned to specific sampling sites. These results demonstrate the potential for this technique to be applied for sub-species characterization of Legionella with significant benefits over established methodologies.

Legionella pneumophila: The Journey from the Environment to the Blood

An outbreak of a potentially fatal form of pneumonia in 1976 and in the annual convention of the American Legion was the first time that Legionella spp. was identified. Thereafter, the term Legionnaires’ disease (LD) was established. The infection in humans is transmitted by the inhalation of aerosols that contain the microorganisms that belong to the Legionellaceae family and the genus Legionella. The genus Legionella contains genetically heterogeneous species and serogroups. The Legionella pneumophila serogroup 1 (Lp1) is the most often detected strain in outbreaks of LD. The pathogenesis of LD infection initiates with the attachment of the bacterial cells to the host cells, and subsequent intracellular replication. Following invasion, Legionella spp. activates its virulence mechanisms: generation of specific compartments of Legionella-containing vacuole (LCV), and expression of genes that encode a type IV secretion system (T4SS) for the translocation of proteins. The ability of L. pneumophila to transmigrate across the lung’s epithelium barrier leads to bacteremia, spread, and invasion of many organs with subsequent manifestations, complications, and septic shock. The clinical manifestations of LD depend on the bacterial load in the aerosol, the virulence factors, and the immune status of the patient. The infection has two distinct forms: the non- pneumatic form or Pontiac fever, which is a milder febrile flu-like illness, and LD, a more severe form, which includes pneumonia. In addition, the extrapulmonary involvement of LD can include heart, brain, abdomen, and joints.

Evaluation of Serotyping of Environmental and Clinical Isolates of Legionella pneumophila using MALDI-TOF MS

Legionella pneumophila (L. pneumophila) is responsible for most Legionnaire's disease cases diagnosed worldwide. The species includes 16 serogroups, but most Legionnaire's disease cases (85.7% in Europe, 87.0% in Japan) are caused by L. pneumophila serogroup 1. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) can be used to identify the L. pneumophila serogroup. In this study, we compared three sample preparation methods that are compatible with MALDI-TOF MS: the direct colony transfer method (DCTM), on-target extraction method (OTEM), and in-tube extraction method (ITEM). The aim was to improve the low identification rates for L. pneumophila, and establish and validate a simple, rapid and robust MALDI-TOF MS-based method for routine use in microbiological laboratories for assignment of L. pneumophila isolates to serogroups and identification of reliable peak biomarkers. Using ITEM, 100.0% (29/29) of hot spring water samples and clinical isolates were correctly identified at the species level. Augmented reference spectra correctly identified all 29 strains at the species level and 29 isolates at the serogroup level, displaying sensitivity, specificity and accuracy of 100.0% for serogroup assignment. MALDI-TOF MS is a relatively inexpensive method for assignment of L. pneumophila serogroups that can serve as a first-line tool for rapid prospective typing.

Production and Characterization of Rat Monoclonal Antibodies against the PAL Antigen of Legionella spp

The purpose of this work was to obtain genus-specific monoclonal antibodies against the Legionella spp. recombinant PAL protein, which will subsequently allow to use them as a basis for the development of new express tests for pathogenic legionella detection. A short three-week immunization protocol for Wistar rats was used to generate rat-mouse heterohybridomas producing antibodies against PAL. Mouse myeloma cell line Sp2/0-Ag14 served as the fusion partner. Hybridization was performed using two methods: PEG-mediated fusion and electrofusion. Subsequent screening was performed by indirect solid-phase ELISA against the target protein rPAL. Specificity analysis was performed by dot-blot using a panel of lysates obtained from 39 pure cultures of different strains, which included closely related and heterologous microorganisms among others. No difference in the efficiency of stable hybridoma clones production by the two indicated cell-fusion methods was detected. Twelve clones producing specific rat monoclonal antibodies were obtained based on the screening results. The obtained rat monoclonal antibodies are highly specific towards the PAL protein of L. pneumophila of different serological groups and other pathogenic legionella and are good candidates to be used as the components of diagnostic test systems for the detection of pathogenic representatives of the Legionella genus.

Legionella pneumophila-Epidemiology and Characterization of Clinical Isolates, Slovenia, 2006-2020

Legionella pneumophila is the causative agent of severe Legionnaires’ disease (LD). Although an increasing number of LD cases have been observed, published data from Slovenia are very limited and data on molecular epidemiology are even scarcer. The present retrospective study (2006–2020) reports the results of the microbiological diagnosis of LD, as well as the epidemiology and characterization of the Legionella clinical isolates. We tested urine samples from 15,540 patients with pneumonia symptoms for L. pneumophila infection by urine antigen test, of which 717 (4.6%) tested positive. Isolation of L. pneumophila was successfully performed from 88 clinical specimens, with 82 (93.2%) being identified as L. pneumophila sg 1 and six (6.8%) as L. pneumophila sg 2–14. Sequence-based typing (SBT) identified 33 different sequence types (STs), the most frequent being ST1 and ST23. Sequence type 1 mainly comprised isolates belonging to the Philadelphia subgroup, and ST23 mostly to Allentown/France. The standard SBT scheme, as well as Dresden phenotyping for L. pneumophila, presented a high diversity among isolates.

Detection of targeted bacteria species on filtration membranes

The detection of pathogens in aquatic environments issues a time-consuming challenge, but it is an essential task to prevent the spread of diseases. We have developed a new point-of-care (POC) method for the fast and efficient detection of Legionella pneumophila in water. The method consists first of the generation of immunocomplexes of bacteria species with its corresponding targeted fluorescence-labelled serogroup-specific antibodies, and second a concentration step of pathogens with a membrane filter. Third, on the filtration membrane, our method can detect the fluorescence intensity corresponding to the pathogen concentration. Thus selective and efficient evidence for the presence of bacteria can be evaluated. We tested our system on fluorescent Escherichia coli bacteria and were able to reach an accurate determination of 1000 cells. The technique was furthermore tested on Legionella pneumophila cells, which were labelled with fluorescence-labelled antibodies as a proof of principle. Furthermore, we were able to verify this method in the presence of other bacteria species. We were able to detect bacteria cells within half an hour, a substantial advancement compared to the prevailling state of the art detection method based on the cultivation of Legionella pneumophila. Hence, this system represents the basis for future developments in analysis of pathogens.

Legionella pneumonia complicated by rhabdomyolysis

Legionnaires' disease is a recognised but rare cause of rhabdomyolysis. It can be further complicated with renal impairment. In this case report, we describe a previously healthy, semiactive 50-year-old man who within days was reduced to having periods of dyspnea after minutes of walking in addition to near fatal acute renal failure. He was found to have the rare triad of Legionella pneumonia, renal failure and rhabdomyolysis, which is associated with high morbidity and mortality. He was treated according to guidelines with azithromycin monotherapy and aggressive fluid hydration. 20 days after admission, the patient was walking independently and discharged home.

Legionella occurrence in municipal and industrial wastewater treatment plants and risks of reclaimed wastewater reuse: Review

Wastewater treatment plants (WWTPs) have been identified as confirmed but until today underestimated sources of Legionella, playing an important role in local and community cases and outbreaks of Legionnaires' disease. In general, aerobic biological systems provide an optimum environment for the growth of Legionella due to high organic nitrogen and oxygen concentrations, ideal temperatures and the presence of protozoa. However, few studies have investigated the occurrence of Legionella in WWTPs, and many questions in regards to the interacting factors that promote the proliferation and persistence of Legionella in these treatment systems are still unanswered. This critical review summarizes the current knowledge about Legionella in municipal and industrial WWTPs, the conditions that might support their growth, as well as control strategies that have been applied. Furthermore, an overview of current quantification methods, guidelines and health risks associated with Legionella in reclaimed wastewater is also discussed in depth. A better understanding of the conditions promoting the occurrence of Legionella in WWTPs will contribute to the development of improved wastewater treatment technologies and/or innovative mitigation approaches to minimize future Legionella outbreaks.

Adaptation of Amoeba Plate Test To Recover Legionella Strains from Clinical Samples

The isolation of Legionella from respiratory samples is the gold standard for diagnosis of Legionnaires' disease (LD) and enables epidemiological studies and outbreak investigations. The purpose of this work was to adapt and to evaluate the performance of an amoebic coculture procedure (the amoeba plate test [APT]) for the recovery of Legionella strains from respiratory samples, in comparison with axenic culture and liquid-based amoebic coculture (LAC). Axenic culture, LAC, and APT were prospectively performed with 133 respiratory samples from patients with LD. The sensitivities and times to results for the three techniques were compared. Using the three techniques, Legionella strains were isolated in 46.6% (n = 62) of the 133 respiratory samples. The sensitivity of axenic culture was 42.9% (n = 57), that of LAC was 30.1% (n = 40), and that of APT was 36.1% (n = 48). Seven samples were positive by axenic culture only; for those samples, there were <10 colonies in total. Five samples, all sputum samples, were positive by an amoebic procedure only (5/5 samples by APT and 2/5 samples by LAC); all had overgrowth by oropharyngeal flora with axenic culture. The combination of axenic culture with APT yielded a maximal isolation rate (i.e., 46.6%). Overall, the APT significantly reduced the median time for Legionella identification to 4 days, compared with 7 days for LAC (P < 0.0001). The results of this study support the substitution of LAC by APT, which could be implemented as a second-line technique for culture-negative samples and samples with microbial overgrowth, especially sputum samples. The findings provide a logical basis for further studies in both clinical and environmental settings.

Prevalence of Infection-Competent Serogroup 6 Legionella pneumophila within Premise Plumbing in Southeast Michigan

Coinciding with major changes to its municipal water system, Flint, MI, endured Legionnaires’ disease outbreaks in 2014 and 2015. By sampling premise plumbing in Flint in the fall of 2016, we found that 12% of homes harbored legionellae, a frequency similar to that in residences in neighboring areas. To evaluate the genetic diversity of Legionella pneumophila in Southeast Michigan, we determined the sequence type (ST) and serogroup (SG) of the 18 residential isolates from Flint and Detroit, MI, and the 33 clinical isolates submitted by hospitals in three area counties in 2013 to 2016. Common to one environmental and four clinical samples were strains of L. pneumophila SG1 and ST1, the most prevalent ST worldwide. Among the Flint premise plumbing isolates, 14 of 16 strains were of ST367 and ST461, two closely related SG6 strain types isolated previously from patients and corresponding environmental samples. Each of the representative SG1 clinical strains and SG6 environmental isolates from Southeast Michigan infected and survived within macrophage cultures at least as well as a virulent laboratory strain, as judged by microscopy and by enumerating CFU. Likewise, 72 h after infection, the yield of viable-cell counts increased >100-fold for each of the representative SG1 clinical isolates, Flint premise plumbing SG6 ST367 and -461 isolates, and two Detroit residential isolates. We verified by immunostaining that SG1-specific antibody does not cross-react with the SG6 L. pneumophila environmental strains. Because the widely used urinary antigen diagnostic test does not readily detect non-SG1 L. pneumophila, Legionnaires’ disease caused by SG6 L. pneumophila is likely underreported worldwide.

L. pneumophila is the leading cause of disease outbreaks associated with drinking water in the United States. Compared to what is known of the established risks of colonization within hospitals and hotels, relatively little is known about residential exposure to L. pneumophila. One year after two outbreaks of Legionnaires’ disease in Genesee County, MI, that coincided with damage to the Flint municipal water system, our multidisciplinary team launched an environmental surveillance and laboratory research campaign aimed at informing risk management strategies to provide safe public water supplies. The most prevalent L. pneumophila strains isolated from residential plumbing were closely related strains of SG6. In laboratory tests of virulence, the SG6 environmental isolates resembled SG1 clinical strains, yet they are not readily detected by the common diagnostic urinary antigen test, which is specific for SG1. Therefore, our study complements the existing epidemiological literature indicating that Legionnaires’ disease due to non-SG1 strains is underreported around the globe.

Outbreak of Legionnaires' disease associated with cooling towers at a California state prison, 2015

A large outbreak of Legionnaires' disease occurred at a California state prison in August 2015. We conducted environmental and epidemiological investigations to identify the most likely source of exposure and characterise morbidity. Sixty-four inmates had probable Legionnaires' disease; 14 had laboratory-confirmed legionellosis. Thirteen (17%) inmates were hospitalised; there were no deaths. Ill inmates were more likely to be ⩾65 years old (P < 0.01), have the chronic obstructive pulmonary disease (P < 0.01), diabetes mellitus (P = 0.02), hepatitis C infection (P < 0.01), or end-stage liver disease (P < 0.01). The case-patients were in ten housing units throughout the prison grounds. All either resided in or were near the central clinical building (for appointments or yard time) during their incubation periods. Legionella pneumophila serogroup 1 was cultured from three cooling towers on top of the central medical clinic (range, 880-1200 cfu/ml). An inadequate water management program, dense biofilm within the cooling towers, and high ambient temperatures preceding the outbreak created an ideal environment for Legionella sp. proliferation. All state prisons were directed to develop local operating procedures for maintaining their cooling towers and the state health department added a review of the maintenance plans to their environmental inspection protocol.

Legionella pneumonia appeared during hospitalization in a patient with hematological malignancy confirmed by sputum culture after negative urine antigen test

Legionella pneumophila is recognized as a common causative organism for community-acquired pneumonia, but it is rarely a causative organism for hospital-acquired pneumonia, except in cases of hospital outbreak. Recently, most of the Legionella cases have been diagnosed using the urine antigen test. However, this test can reliably detect only L. pneumophila serogroup 1. Here we report a 63-year-old male patient who was recently diagnosed with acute leukemia and treated with chemotherapy and who developed pneumonia on hospital day 8 during the nadir phase. He was later diagnosed with Legionella pneumonia by culture despite a negative urine antigen test. This case suggests that Legionella pneumonia is an important differential diagnosis for pneumonia in inpatients in the early phase of hospitalization and that when Legionella infection is clinically suspected, culture using selective media or molecular tests should be performed even if the urine antigen test is negative.

Microbiology and Epidemiology of Legionnaire's Disease

Legionnaire's disease (LD) is the pneumonic form of legionellosis caused by aerobic gram-negative bacilli of the genus Legionella. Individuals become infected when they inhale aerosolized water droplets contaminated with Legionella species. Forty years after the identification of Legionella pneumophila as the cause of the 1976 pneumonia outbreak in a hotel in Philadelphia, we have non-culture-based diagnostic tests, effective antibiotics, and preventive measures to handle LD. With a mortality rate still around 10%, underreporting, and sporadic outbreaks, there is still much work to be done. In this article, the authors review the microbiology, laboratory diagnosis, and epidemiology of LD.

Legionella pneumonia associated with severe acute respiratory distress syndrome and diffuse alveolar hemorrhage - A rare association

Legionella pneumophila is a common, usually underreported and undiagnosed cause of community acquired pneumonia which can lead to significant morbidity and mortality. Diffuse alveolar hemorrhage rarely have been associated with legionella infection. We present a 61-year-old man with hypertension, diabetes mellitus and obesity admitted with severe acute respiratory distress syndrome. He was found to have Legionella pneumonia with associated diffuse alveolar hemorrhage diagnosed with bronchoscopic sequential bronchoalveolar lavage. He was successfully managed with antibiotics, lung protective strategies and intravenous pulse dose steroids. This patient highlights the unusual association of Legionella infection and diffuse alveolar hemorrhage. Additionally, the case re-enforces the need for early and aggressive evaluation and management of patients presenting with pneumonia and progressive hypoxia despite adequate treatment.

Legionnaires' disease at a medical center in southern Taiwan

BACKGROUND/PURPOSE

Legionella pneumophila had been recognized as a pathogen for both healthcare-associated and community-acquired pneumonia. We aimed to evaluate clinical features and outcomes of patients with Legionnaires' disease at a tertiary medical center in southern Taiwan.

METHODS

From January 2005 to December 2013, a retrospective study of adult cases of Legionnaires' disease was conducted in a 1200-bed tertiary hospital. Their medical records were reviewed for further evaluation and analysis.

RESULTS

A total of 61 cases of Legionnaires' disease were identified during the study period. Their mean age was 61.1 years, with male predominance (43, 70.5%). Among them, 30 (49.2%) had healthcare-associated pneumonia (HCAP), 20 (32.8%) had community-acquired pneumonia, and notably 11 (18.0%) were caregivers. Patients with healthcare-associated pneumonia tend to have higher Charlson comorbidity scores than those with community-acquired pneumonia (3.6±2.4 vs. 1.9±1.9, p=0.008) and caregivers (0.5±0.5, p<0.001). Six patients died, resulting in an in-hospital mortality rate of 9.8%. Underlying cancer (66.7% vs. 20.0%, p=0.028) and a higher Charlson comorbidity score (4.7±2.6 vs. 2.2±2.2, p=0.013) were related to a fatal outcome.

CONCLUSION

L. pneumophila remains an important pathogen for pneumonia acquired from the community or associated with healthcare facility. Healthy caregivers may potentially be at risk for Legionella infection in certain clinical settings.

Legionella pneumonia in the Niagara Region, Ontario, Canada: a case series

BACKGROUND

Legionella pneumophila, a major cause of Legionnaires' disease, accounts for 2-15 % of all community-acquired pneumonia requiring hospitalization and up to 30 % of community-acquired pneumonia requiring intensive care unit admission. Early initiation of appropriate antimicrobial therapy is a crucial step in the prevention of morbidity and mortality. However, recognition of Legionnaires' disease continues to be challenging because of its nonspecific clinical features. We sought to describe hospitalized community-acquired Legionnaires' disease to increase awareness of this important and potentially lethal disease.

METHODS

A retrospective multicenter observational study was conducted with all patients with confirmed Legionnaires' disease in the Niagara Region of the Province of Ontario, Canada, from June to December 2013.

RESULTS

From June to December 2013, there were 14 hospitalized cases of Legionnaires' disease in the Niagara Region. Of these, 86 % (12 patients) had at least one comorbidity and 71 % (10 patients) were cigarette smokers. In our cohort, Legionnaires' disease was diagnosed with a combination of a urinary Legionella antigen test and a Legionella real-time polymerase chain reaction assay. Delay in effective antimicrobial therapy in the treatment of Legionella infection led to clinical deterioration. The majority of patients had met systemic inflammatory response syndrome criteria with fever >38 °C (71 %), heart rate >90 beats per minute (71 %), and respiratory rate >20 breaths per minute (86 %). Eleven patients (79 %) required admission to the intensive care unit or step-down unit, and nine patients (64 %) required intubation. Clinical improvement after initiation of antimicrobials was protracted.

CONCLUSIONS

Legionnaires' disease should be considered during the late spring and summer months in patients with a history of tobacco use and various comorbidities. Clinically, patients presented with severe, nonspecific, multisystem disease characterized by shortness of breath, abnormal vital signs, and laboratory derangements including hyponatremia, elevated creatine kinase, and evidence of organ dysfunction. In addition, antimicrobial therapy with newer macrolides or respiratory fluoroquinolones should be initiated for severe community-acquired pneumonia requiring intensive care unit admission, prior to laboratory confirmation of diagnosis, especially when a clinical suspicion of Legionella infection exists.

The life stage-specific pathometabolism of Legionella pneumophila

The genus Legionella belongs to Gram-negative bacteria found ubiquitously in aquatic habitats, where it grows in natural biofilms and replicates intracellularly in various protozoa (amoebae, ciliates). L. pneumophila is known as the causative agent of Legionnaires' disease, since it is also able to replicate in human alveolar macrophages, finally leading to inflammation of the lung and pneumonia. To withstand the degradation by its host cells, a Legionella-containing vacuole (LCV) is established for intracellular replication, and numerous effector proteins are secreted into the host cytosol using a type four B secretion system (T4BSS). During intracellular replication, Legionella has a biphasic developmental cycle that alternates between a replicative and a transmissive form. New knowledge about the host-adapted and life stage-dependent metabolism of intracellular L. pneumophila revealed a bipartite metabolic network with life stage-specific usages of amino acids (e.g. serine), carbohydrates (e.g. glucose) and glycerol as major substrates. These metabolic features are associated with the differentiation of the intracellular bacteria, and thus have an important impact on the virulence of L. pneumophila.

Community-acquired pneumonia related to intracellular pathogens

Community-acquired pneumonia (CAP) is associated with high rates of morbidity and mortality worldwide; the annual incidence of CAP among adults in Europe has ranged from 1.5 to 1.7 per 1000 population. Intracellular bacteria are common causes of CAP. However, there is considerable variation in the reported incidence between countries and change over time. The intracellular pathogens that are well established as causes of pneumonia are Legionella pneumophila, Mycoplasma pneumoniae, Chlamydophila pneumoniae, Chlamydophila psittaci, and Coxiella burnetii. Since it is known that antibiotic treatment for severe CAP is empiric and includes coverage of typical and atypical pathogens, microbiological diagnosis bears an important relationship to prognosis of pneumonia. Factors such as adequacy of initial antibiotic or early de-escalation of therapy are important variables associated with outcomes, especially in severe cases. Intracellular pathogens sometimes appear to cause more severe disease with respiratory failure and multisystem dysfunction associated with fatal outcomes. The clinical relevance of intracellular pathogens in severe CAP has not been specifically investigated. We review the prevalence, general characteristics, and outcomes of severe CAP cases caused by intracellular pathogens.

Legionnaires' disease

Since first identified in early 1977, bacteria of the genus Legionella are recognised as a common cause of community-acquired pneumonia and a rare cause of hospital-acquired pneumonia. Legionella bacteria multisystem manifestations mainly affect susceptible patients as a result of age, underlying debilitating conditions, or immunosuppression. Water is the major natural reservoir for Legionella, and the pathogen is found in many different natural and artificial aquatic environments such as cooling towers or water systems in buildings, including hospitals. The term given to the severe pneumonia and systemic infection caused by Legionella bacteria is Legionnaires' disease. Over time, the prevalence of legionellosis or Legionnaires' disease has risen, which might indicate a greater awareness and reporting of the disease. Advances in microbiology have led to a better understanding of the ecological niches and pathogenesis of the condition. Legionnaires' disease is not always suspected because of its non-specific symptoms, and the diagnostic tests routinely available do not offer the desired sensitivity. However, effective antibiotics are available. Disease notification systems provide the basis for initiating investigations and limiting the scale and recurrence of outbreaks. This report reviews our current understanding of this disease.

PCR method for the rapid detection and discrimination of Legionella spp. based on the amplification of pcs, pmtA, and 16S rRNA genes

Legionella bacteria are organisms of public health interest due to their ability to cause pneumonia (Legionnaires' disease) in susceptible humans and their ubiquitous presence in water supply systems. Rapid diagnosis of Legionnaires' disease allows the use of therapy specific for the disease. L. pneumophila serogroup 1 is the most common cause of infection acquired in community and hospital environments. The non-L. pneumophila infections are likely under-detected because of a lack of effective diagnosis. In this work, simplex and duplex PCR assays with the use of new molecular markers pcs and pmtA involved in phosphatidylcholine synthesis were specified for rapid and cost-efficient identification and distinguishing Legionella species. The sets of primers developed were found to be sensitive and specific for reliable detection of Legionella belonging to the eight most clinically relevant species. Among these, four primer sets I, II, VI, and VII used for duplex-PCRs proved to have the highest identification power and reliability in the detection of the bacteria. Application of this PCR-based method should improve detection of Legionella spp. in both clinical and environmental settings and facilitate molecular typing of these organisms.

Current and emerging Legionella diagnostics for laboratory and outbreak investigations

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.

Aetiology, source and prevention of waterborne healthcare-associated infections: a review

The purpose of this review is to discuss the scientific literature on waterborne healthcare-associated infections (HCAIs) published from 1990 to 2012. The review focuses on aquatic bacteria and describes both outbreaks and single cases in relation to patient characteristics, the settings and contaminated sources. An overview of diagnostic methods and environmental investigations is summarized in order to provide guidance for future case investigations. Lastly, on the basis of the prevention and control measures adopted, information and recommendations are given. A total of 125 reports were included, 41 describing hospitalized children. All cases were sustained by opportunistic pathogens, mainly Legionellaceae, Pseudomonadaceae and Burkholderiaceae. Hot-water distribution systems were the primary source of legionnaires’ disease, bottled water was mainly colonized by Pseudomonaceae, and Burkholderiaceae were the leading cause of distilled and sterile water contamination. The intensive care unit was the most frequently involved setting, but patient characteristics were the main risk factor, independent of the ward. As it is difficult to avoid water contamination by microbes and disinfection treatments may be insufficient to control the risk of infection, a proactive preventive plan should be put in place. Nursing staff should pay special attention to children and immunosuppressed patients in terms of tap-water exposure and also their personal hygiene, and should regularly use sterile water for rinsing/cleaning devices.

Development of a prototype lateral flow immunoassay (LFI) for the rapid diagnosis of melioidosis

Burkholderia pseudomallei is a soil-dwelling bacterium and the causative agent of melioidosis. Isolation of B. pseudomallei from clinical samples is the “gold standard” for the diagnosis of melioidosis; results can take 3–7 days to produce. Alternatively, antibody-based tests have low specificity due to a high percentage of seropositive individuals in endemic areas. There is a clear need to develop a rapid point-of-care antigen detection assay for the diagnosis of melioidosis. Previously, we employed In vivo Microbial Antigen Discovery (InMAD) to identify potential B. pseudomallei diagnostic biomarkers. The B. pseudomallei capsular polysaccharide (CPS) and numerous protein antigens were identified as potential candidates. Here, we describe the development of a diagnostic immunoassay based on the detection of CPS. Following production of a CPS-specific monoclonal antibody (mAb), an antigen-capture immunoassay was developed to determine the concentration of CPS within a panel of melioidosis patient serum and urine samples. The same mAb was used to produce a prototype Active Melioidosis Detect Lateral Flow Immunoassay (AMD LFI); the limit of detection of the LFI for CPS is comparable to the antigen-capture immunoassay (∼0.2 ng/ml). The analytical reactivity (inclusivity) of the AMD LFI was 98.7% (76/77) when tested against a large panel of B. pseudomallei isolates. Analytical specificity (cross-reactivity) testing determined that 97.2% of B. pseudomallei near neighbor species (35/36) were not reactive. The non-reactive B. pseudomallei strain and the reactive near neighbor strain can be explained through genetic sequence analysis. Importantly, we show the AMD LFI is capable of detecting CPS in a variety of patient samples. The LFI is currently being evaluated in Thailand and Australia; the focus is to optimize and validate testing procedures on melioidosis patient samples prior to initiation of a large, multisite pre-clinical evaluation.

Burkholderia pseudomallei is an environmental bacterium and the cause of melioidosis. Culture of patient samples is the “gold standard” diagnostic test, but may take up to 7 days to complete. Melioidosis has a 10–40% case fatality rate depending on the geographic location. Delays in diagnosis could lead to administration of ineffective antimicrobial therapy, since B. pseudomallei is resistant to empiric antibiotic regimens. Therefore, we have developed a lateral flow immunoassay that can be used in the clinical setting to diagnose melioidosis in 15 minutes. The test promises to provide improved management of patients with melioidosis.

Facets of small RNA-mediated regulation in Legionella pneumophila

Legionella pneumophila is a water-borne pathogen that causes a severe lung infection in humans. It is able to replicate inside amoeba in the water environment, and inside lung macrophages in humans. Efficient regulation of gene expression is critical for responding to the conditions that L. pneumophila encounters and for intracellular multiplication in host cells. In the last two decades, many reports have contributed to our understanding of the critical importance of small regulatory RNAs (sRNAs) in the regulatory network of bacterial species. This report presents the current state of knowledge about the sRNAs expressed by L. pneumophila and discusses a few regulatory pathways in which sRNAs should be involved in this pathogen.