Controlling Legionella pneumophila growth in hot water systems by reducing dissolved oxygen levels.

Legionella pneumophila, the leading cause of Legionnaires' disease in the United States, is found in lakes, ponds, and streams but poses a health risk when it grows in building water systems. The growth of L. pneumophila in hot water systems of healthcare facilities poses a significant risk to patients, staff, and visitors. Hospitals and long-term care facilities account for 76% of reported Legionnaires' disease cases with mortality rates of 25%. Controlling L. pneumophila growth in hot water systems serving healthcare and hospitality buildings is currently achieved primarily by adding oxidizing chemical disinfectants. Chemical oxidants generate disinfection byproducts and can accelerate corrosion of premise plumbing materials and equipment. Alternative control methods that do not generate hazardous disinfection byproducts or accelerate corrosion are needed. L. pneumophila is an obligate aerobe that cannot sustain cellular respiration, amplify, or remain culturable when dissolved oxygen (DO) concentrations are too low (< 0.3 mg/L). An alternative method of controlling L. pneumophila growth by reducing DO levels in a hot water model system using a gas transfer membrane contactor was evaluated. A hot water model system was constructed and inoculated with L. pneumophila at DO concentrations above 0.5 mg/L. Once the model system was colonized, DO levels were incrementally reduced. Water samples were collected each week to evaluate the effect of reducing dissolved oxygen levels when all other conditions favored Legionella amplification. At DO concentrations below 0.3 mg/L, L. pneumophila concentrations were reduced by 1-log over 7 days. Under conditions in the hot water model system, at favorable temperatures and with no residual chlorine disinfectant, L. pneumophila concentrations were reduced by 1-log, indicating growth inhibition by reducing DO levels as the sole control measure. In sections of the model system where DO levels were not lowered L. pneumophila continued to grow. Reducing dissolved oxygen levels in hot water systems of healthcare and other large buildings to control L. pneumophila could also lower the risk of supplemental chemical treatment methods currently in use.

An Epidemiological Study on Legionnaires' Disease in Gyeonggi Province, Korea: Occurrence, Infection Routes, and Risk Factors for Mortality (2016-2022).

Background and Objectives: Legionnaires' disease (LD) is an acute respiratory disease with increasing annual numbers of reported domestic and global cases. This study aimed to establish foundational data for the prevention and control of LD by investigating the occurrence and infection routes of reported and suspected cases of LD in Gyeonggi Province, Korea, from January 2016 to December 2022, and by and analyzing the risk factors for death. Materials and Methods: A sex-and-age standardization was performed on LD patients and suspected cases reported in Gyeonggi Province. The monthly average number of confirmed cases was visualized using graphs, and a survival analysis was performed using Kaplan-Meier survival curves. The mortality risk ratio was estimated using the Cox proportional hazards model. Results: The incidence of LD in Gyeonggi Province mirrored the national trend, peaking in July with the highest number of confirmed and suspected cases. While there was no significant difference in survival rates by age, the survival rate was higher for suspected cases when analyzed separately. Comparing the death ratio by infection route, nosocomial infections showed the highest death ratio, and intensive care unit (ICU) admission and the presence of coinfections were significantly correlated with mortality. Factors such as nosocomial infection, admission within 1 to 3 days following diagnosis, and the development of complications were factors contributing to a higher risk of death. Conclusions: The general characteristics of patients with LD were similar to those suggested by previous studies. The proportion of community-acquired infections was lower than in previous studies, but the length of hospital stay was similar for survivors and the deceased, and the mortality rate within 30 days after diagnosis was higher for nosocomial infections. In conclusion, nosocomial infection, a period of up to 3 days from admission to diagnosis, and complications were significantly related to the mortality rate of LD.

Factors Associated with Legionella Detection in the Water Systems of National Lodging Organization Facilities with Water Management Programs in the United States.

A better understanding of risk factors and the predictive capability of water management program (WMP) data in detecting Legionella are needed to inform the efforts aimed at reducing Legionella growth and preventing outbreaks of Legionnaires' disease. Using WMPs and Legionella testing data from a national lodging organization in the United States, we aimed to (1) identify factors associated with Legionella detection and (2) assess the ability of WMP disinfectant and temperature metrics to predict Legionella detection. We conducted a logistic regression analysis to identify WMP metrics associated with Legionella serogroup 1 (SG1) detection. We also estimated the predictive values for each of the WMP metrics and SG1 detection. Of 5435 testing observations from 2018 to 2020, 411 (7.6%) had SG1 detection, and 1606 (29.5%) had either SG1 or non-SG1 detection. We found failures in commonly collected WMP metrics, particularly at the primary test point for total disinfectant levels in hot water, to be associated with SG1 detection. These findings highlight that establishing and regularly monitoring water quality parameters for WMPs may be important for preventing Legionella growth and subsequent disease. However, while unsuitable water quality parameter results are associated with Legionella detection, this study found that they had poor predictive value, due in part to the low prevalence of SG1 detection in this dataset. These findings suggest that Legionella testing provides critical information to validate if a WMP is working, which cannot be obtained through water quality parameter measurements alone.

Automated cooling tower detection through deep learning for Legionnaires' disease outbreak investigations: a model development and validation study.

BACKGROUND: Cooling towers containing Legionella spp are a high-risk source of Legionnaires' disease outbreaks. Manually locating cooling towers from aerial imagery during outbreak investigations requires expertise, is labour intensive, and can be prone to errors. We aimed to train a deep learning computer vision model to automatically detect cooling towers that are aerially visible. METHODS: Between Jan 1 and 31, 2021, we extracted satellite view images of Philadelphia (PN, USA) and New York state (NY, USA) from Google Maps and annotated cooling towers to create training datasets. We augmented training data with synthetic data and model-assisted labelling of additional cities. Using 2051 images containing 7292 cooling towers, we trained a two-stage model using YOLOv5, a model that detects objects in images, and EfficientNet-b5, a model that classifies images. We assessed the primary outcomes of sensitivity and positive predictive value (PPV) of the model against manual labelling on test datasets of 548 images, including from two cities not seen in training (Boston [MA, USA] and Athens [GA, USA]). We compared the search speed of the model with that of manual searching by four epidemiologists. FINDINGS: The model identified visible cooling towers with 95·1% sensitivity (95% CI 94·0-96·1) and a PPV of 90·1% (95% CI 90·0-90·2) in New York City and Philadelphia. In Boston, sensitivity was 91·6% (89·2-93·7) and PPV was 80·8% (80·5-81·2). In Athens, sensitivity was 86·9% (75·8-94·2) and PPV was 85·5% (84·2-86·7). For an area of New York City encompassing 45 blocks (0·26 square miles), the model searched more than 600 times faster (7·6 s; 351 potential cooling towers identified) than did human investigators (mean 83·75 min [SD 29·5]; mean 310·8 cooling towers [42·2]). INTERPRETATION: The model could be used to accelerate investigation and source control during outbreaks of Legionnaires' disease through the identification of cooling towers from aerial imagery, potentially preventing additional disease spread. The model has already been used by public health teams for outbreak investigations and to initialise cooling tower registries, which are considered best practice for preventing and responding to outbreaks of Legionnaires' disease. FUNDING: None.

Legionella pneumophila: un patógeno emergente en Argentina / Legionella pneumophila: an emerging pathogen in Argentina

La enfermedad del Legionario es causada por bacterias pertenecientes al género Legionella, siendo la especie pneumophila el principal agente etiológico de esta patología. Esta bacteria se describió por primera vez en 1977 como causa de un brote de neumonía grave registrado en 1976 en un centro de convenciones en los Estados Unidos de América. La enfermedad se presenta como una neumonía atípica, responsable del 1 al 15 % de los casos de neumonías adquiridas en la comunidad (NAC), del 5 al 10% de neumonías del adulto y del 1% en menores de 15 años. Los miembros de la familia Legionellaceae son bacilos aeróbicos gramnegativos que crecen lentamente y se encuentran ampliamente distribuidos en cuerpos de agua. La forma más común de transmisión de Legionella spp es la inhalación de aerosoles contaminados generados a partir de fuentes de agua artificiales. Se asocian con la aparición de brotes esporádicos y epidémicos en la comunidad y en infecciones nosocomiales. Las especies pertenecientes al género Legionella se consideran patógenos emergentes transmitidos por el agua. El objetivo de este trabajo es realizar una revisión sobre las manifestaciones y presentaciones clínicas de la infección causada por L. pneumophila, en virtud de que es considerado mundialmente un patógeno emergente y por existir evidencias de su presencia en sistemas de almacenamiento de agua tratada en la región nordeste de la República Argentina, razón primordial para alertar y actualizar conocimientos al respecto

Legionnaires' disease is caused by bacteria belonging to the genus Legionella, being the pneumophila specie the main etiological agent of this pathology. This bacterium was first described in 1977 as the cause of a severe pneumonia outbreak in 1976 at a convention center in the United States of America. The disease presents as an atypical pneumonia, responsible for 1% to 15% of cases of community-acquired pneumonia (CAP), 5% to 10% of pneumonia in adults and 1% in children under 15 years of age. Members of the Legionellaceae family are aerobic, gram-negative rods that grow slowly and are widely distributed in water bodies. The most common way of transmission of Legionella spp is the inhalation of contaminated aerosols generated from artificial water sources. They are associated with the appearance of sporadic and epidemic outbreaks in the community and in nosocomial infections. Species belonging to the genus Legionella are considered emerging waterborne pathogens.The aim of this work is to carry out a review on the manifestations and clinical presentations of the infection caused by L. pneumophila, due to that it is considered an emerging pathogen worldwide and because there is evidence of its presence in storage systems of treated water in the Northeast region of the Argentine Republic, primary reason to alert and update knowledge in this regard.

Cumplimiento de los protocolos de prevención de la legionelosis en edificios públicos / Legionnaires' disease prevention protocol performance in public buildings

Objetivo Investigar la relación entre el cumplimiento del Real Decreto 865/2003 y el Decreto 287/2002, por los que se establecen los criterios higiénico-sanitarios para la prevención y control de la legionelosis, y el riesgo debido a un deficiente mantenimiento higiénico- preventivo de las instalaciones de agua. Métodos Estudio descriptivo realizado en la provincia de Málaga (España) sobre una muestra correspondiente a 214 edificios públicos, 83 variables e interpretación sobre el porcentaje de cumplimiento de la normativa. Medida del riesgo, definición de clusters (tipificación del riesgo), estimadores clásicos y robustos, estimación jackknife e intervalos de confianza bootstrap . Resultados Riesgo por incumplimiento parcial entre el 11,1 (riego, Centros Privados de ESO) y 85,7 por ciento (AFS, Institutos de Educación Secundaria). La normativa se cumple en 82 edificios, 130 la incumplen y 2 no presentan instalaciones de riesgo. Cumplimiento total 38 por ciento. Estimación para el cumplimiento parámetros de localización 0,33-0,36 (33-36 por ciento) y de escala 0,11-0,16. Estimador jackknife del sesgo reducido 0,35071 (estimación media). Intervalos de confianza bootstrap con extremos [0.26, 0.47]. Conclusión El menor riesgo por incumplimiento parcial corresponde a Institutos de Educación Secundaria y el mayor por distribución a los hoteles de cuatro y tres estrellas. Selección del parámetro de localización estimador de Huber y de escala NMAD . Atendiendo al parámetro "razón poblacional" y estimador "razón muestral", el estimador jackknife del sesgo reducido es insesgado. Intervalos de confianza basados en las técnicas bootstrap , partiendo de la media 0,2- recortada muestral y coeficiente de confianza 0,95, muy aproximados.

Objective Studying the relationship between fulfilment of royal decree 865/2003 and decree 287/2002 (establishing hygienic-sanitary criteria for preventing and controlling Legionnaires' disease) and risk arising from deficient preventative-hygienic water facility maintenance. Methods This was a descriptive study carried out in the province of Málaga (Spain) on a sample of 214 public buildings using 83 variables and interpreting legislation fulfilment percentages. Risks were measured, clusters defined (related to risk typification) and classic and robust estimators, jack-knife estimation and bootstrap confidence intervals were calculated. Results 11.1 percent (irrigation, ESO private centres) and 85.7 percent (AFS, secondary education institutions) partial non-fulfilment/breach risks were found. Eighty-two buildings complied with current standards, 130 failed to fulfil them and 2 did not display risk facilities. There was 38 percent overall compliance with established norms. Location parameter fulfilment was estimated as being 0.33-0.36 (3336 percent) and scale as 0.110.16. Reduced bias jack-knife estimator was 0.35071 (average estimation). Bootstrap confidence interval extremes were 0.26 and 0.47. Conclusion Secondary education institutions represented the least risk due to partial noncompliance and four- and three-star hotels the greatest. Huber estimator was selected as location parameter and NMAD as scale parameter. Regarding the population ratio parameter and sample ratio estimator, it was considered that the jack-knife estimator of reduced bias was unbiased. Confidence intervals based on bootstrap techniques (starting from 0.2trimmed mean sample and a 0.95 confidence coefficient) were very approximate.

Agregación de casos de neumonía por Legionella en trabajadores relacionados con la industria de la cerámica en Castellón en 2006 / Aggregation of caes of Legionalla pneumonia in workers related to the ceramic industry in Castellon, Spain, 2006

Fundamento. Los casos de la legionelosis en ocasiones se presentan en forma de agregaciones que son difíciles de interpretar. Analizamos aquí una de estas agrupaciones ocurrida durante un verano en Castellón. Métodos. Se aplicaron métodos microbiologicos, clínicos y de epidemiología de campo. Resultados. En pocos días hubo 5 casos de neumonía por Legionella en trabajadores relacionados con varias industrias de la cerámica, en un área donde existe una alta concentración de estas fábricas. Dos de ellos, constituyeron un pequeño brote. Mediante técnicas de biología molecular de las cepas se descartó el origen común de tres de los casos. Conclusiones. Se discute si este episodio de un brote surgido en el contexto de un cluster más amplio de casos de origen multifocal fue un hecho casual o fue la expresión de un riesgo relacionado con esa actividad industrial que pudiera repetirse (AU)

Background. Cases of legionellosis sometimes arise in the form of aggregations which are difficult to interpret. This study provides an analysis of these groupings having arisen one summer in Castellon. Methods. Microbiological, clinical and epidemiological field methods were employed. Results. Within a few days, there were five (5) cases of legionella pneumonia in workers related to various ceramic industries within an area where a large number of these plants are located. Two constituted a minor outbreak. By means of molecular biology techniques performed on the strains, the common origins of three of the cases were ruled out. Conclusions. It is debated whether this episode of an outbreak having arisen within the context of a broader-ranging cluster of cases of a multi-focal origin was a chance event or whether it was the manifestation of a risk related to this industrial activity which might repeat itself (AU)

Doença dos legionários: uma revisão / Legionnaire's disease: a review

A doença dos legionários é uma patologia autolimitada semelhante à gripe, caracterizada por febre, cefaléia, mialgias e tosse não produtiva, estando, algumas vezes, relacionada com formas fatais de pneumonia. Tem como etiologia a infecção pela bactéria Legionella sp. Atualmente são conhecidas cerca de 40 espécies de Legionella, mas apenas cinco causam a doença em humanos.Legionella pneumophila é a principal espécie relacionada a casos em humanos. As legionelas encontram-se freqüentemente em reservatórios de água e crescem em água quente. Os sistemas de distribuição de água quente e as torres de resfriamento dos equipamentos de ar condicionado são identificados como as principais fontes de infecção. Vários testes laboratoriais estão disponíveis para o diagnóstico de legionela, incluindo cultura, aglutinação em lâmina com partículas de látex, radioimunoensaio, imunofluorescência direta e indireta e enzimaimunoensaio. O objetivo principal da vigilância da doença do legionário é a identificação de surtos, de forma a implementar medidas de controle. O presente trabalho descreve uma revisão sobre a doença dos legionários, visando a ampliar o conhecimento dos profissionais da saúde e da população em geral.

Legionnaire’s disease is a self-limiting pathology. Similar to cold, it is characterized by fever, headache, myalgias and non-productive cough, and sometimes connected with fatal pneumonia. Its etiology to infection is done through bacteria Legionella spp. Presently, about forty types of Legionella are known, but only five of them can cause disease to human beings. Legionella pneumphila is the main type related to human beings. Legionellas are usually found in water reservoirs, and grow in hot water. Both hot water distribution systems and air-conditioner tower cooling are identified as the main sources of infection. Many laboratory tests are available for Legionella diagnosis, including culture, agglutination on blade containing latex particles radioimmunoassay, direct and indirect immunofluorescence, and enzyme-linked immunosorbent assay. The main objective in checking legionnaire’s disease is to identify outbreaks, aiming at implementing control measurements. This article describes a review of legionnaire’s disease, intending to enlarge health professional and ordinary people’s knowledge on the field.