Legionella Control Research Articles

Colonization of a therapeutic spa with Legionella spp: a public health issue

Traditional geothermally heated therapeutic spas, widely distributed in Europe, use water that is not disinfected. The colonization of therapeutic spas by Legionella spp. has been reported and several outbreaks and sporadic cases of legionellosis have been associated with the use of these facilities. We tested the effectiveness of hyperchlorination and the combination of hyperchlorination and ultraviolet light (UV) disinfection against legionellae which were persistently detected in the water used to supply the therapeutic spa. The hyperchlorination of the water distribution system was performed with a free residual chlorine concentration of 50 mg/l for 4 h. An initial reduction in the numbers of legionellae was determined, but it rapidly increased to the original values. A UV unit was installed at the entrance to the spa's water distribution system and a new hyperchlorination procedure was performed immediately before UV irradiation (40 mJ/cm 2), which was in use continuously for a nine-month period. While legionellae were not recovered during the irradiation period, these organisms were detected immediately after deactivation of the UV unit. We demonstrated that UV disinfection provides effective control of Legionella spp., with the advantage of being a method that, unlike chemical disinfectants, does not affect the physicochemical composition of the water. These findings suggest that UV irradiation, applied at key points in therapeutic spas, can be used to control colonization of water distribution systems by Legionella spp.

Evaluation of power ultrasound for disinfection of both Legionella pneumophila and its environmental host Acanthamoeba castellanii

The objectives of this study were to (1) examine the effect of power ultrasound on the viability of both Legionella pneumophila and Acanthamoeba castellanii trophozoites and cysts, (2) investigate if intracellular Legionella replication in trophozoites positively affects bacterial resistance to ultrasound and (3) study if Legionella renders viable but non-culturable (VBNC) due to ultrasound treatments. Using laboratory scale experiments, microorganisms were exposed for various time periods to power ultrasound at a frequency of 36 kHz and an ultrasound power setting of 50 and 100%. Due to a fast destruction, trophozoite hosts were not able to protect intracellular Legionella from eradication by ultrasound, in contrast to cysts. No significant effects of ultrasound on cyst viability could be detected and power settings of 100% for 30 min only made intracellular Legionella concentrations decrease with 1.3 log units. Due to intracellular replication of Legionella in trophozoites, ultrasound no longer affected bacterial viability. Concerning the VBNC state, ultrasound treatments using a power setting of 50% partly induced Legionella (±7%) to transform into VBNC bacteria, in contrast to power settings of 100%. Promising results obtained in this study indicate the possible application of power ultrasound in the control of both Legionella and Acanthamoeba concentrations in anthropogenic water systems.

Legionella species colonization in cooling towers: Risk factors and assessment of control measures

Cooling towers can be colonized by Legionella spp, and inhalation of aerosols generated by their operation may cause Legionnaires' disease in susceptible hosts. Environmental investigations of Legionnaires' disease outbreaks linked with cooling towers have revealed poorly maintained systems, lack of control measures, and failure of system equipment. The purpose of this study was to identify Legionella-contaminated cooling towers, identify risk factors for contamination, and assess the effectiveness of control measures. A total of 96 cooling towers of public buildings were registered and inspected, and 130 samples were collected and microbiologically tested. Microbiological test results were associated with characteristics of cooling towers, water samples, inspection results, and maintenance practices. Of the total 96 cooling towers examined, 47 (48.9%) were colonized by Legionella spp, and 22 (22.9%) required remedial action. A total of 65 samples (50.0%) were positive (> or = 500 cfu L(-1)), and 30 (23%) were heavily contaminated (> or = 10(4) cfu L(-1)). Of the 69 isolates identified, 55 strains (79.7.%) were L pneumophila. Legionella colonization was positively associated with the absence of training on Legionella control (relative risk [RR] = 1.66; P = .02), absence of regular Legionella testing (RR = 2.07: P = .002), absence of sunlight protection (RR = 1.63: P = .02), with samples in which the free residual chlorine level in the water sample was < 0.5 mg/L (RR = 2.23; P = .01), and with total plate count (P =.001). Colonization was negatively associated with chemical disinfection (RR = 0.2; P = .0003) and with the presence of a risk assessment and management plan (RR = 0.12; P = .0005). A statistically significant higher age (P =.01) was found in legionellae-positive cooling towers (median, 17 years; interquartile range [IQR] =5.0 to 26.0 years) compared with noncolonized cooling towers (median age, 6 years; IQR =1.0 to 13.5 years). After the 22 legionellae-positive cooling towers were disinfected with chlorine, 2 (9%) of them remained positive for Legionella spp with a concentration > or = 1000 cfu L(-1). Cooling towers can be heavily colonized by Legionella spp and thus present a potential risk for infection. This study demonstrates the importance of a risk assessment and management plan. Water chlorination effectively reduces legionellae contamination. Proper training of cooling tower operators is paramount.

Galp Energia to use UOP/Eni technology

Traditional geothermally heated therapeutic spas, widely distributed in Europe, use water that is not disinfected. The colonization of therapeutic spas by Legionella spp. has been reported and several outbreaks and sporadic cases of legionellosis have been associated with the use of these facilities. We tested the effectiveness of hyperchlorination and the combination of hyperchlorination and ultraviolet light (UV) disinfection against legionellae which were persistently detected in the water used to supply the therapeutic spa. The hyperchlorination of the water distribution system was performed with a free residual chlorine concentration of 50 mg/l for 4 h. An initial reduction in the numbers of legionellae was determined, but it rapidly increased to the original values. A UV unit was installed at the entrance to the spa's water distribution system and a new hyperchlorination procedure was performed immediately before UV irradiation (40 mJ/cm2), which was in use continuously for a nine-month period. While legionellae were not recovered during the irradiation period, these organisms were detected immediately after deactivation of the UV unit. We demonstrated that UV disinfection provides effective control of Legionella spp., with the advantage of being a method that, unlike chemical disinfectants, does not affect the physicochemical composition of the water. These findings suggest that UV irradiation, applied at key points in therapeutic spas, can be used to control colonization of water distribution systems by Legionella spp.

Legionnaires' disease: evaluation of a quantitative microbial risk assessment model

The quantities of Legionella vary considerably from natural waters to water in contaminated domestic hot water supplies, whirlpool spas and cooling towers, with the risk for LD rising as the Legionella counts grow. We currently report the results from our Quantitative Microbial Risk Assessment (QMRA) model evaluation. We developed the LD QMRA model to better understand Legionella exposure risks. Using an animal data derived model for LD, we calculated risks from estimated exposures for a whirlpool spa outbreak, two hot spring spa outbreaks and compared the results to the reported LD risks. The QMRA model shows agreement (generally less than an order of magnitude discrepancy) with the reported Legionnaires' disease sub-clinical severity infection, clinical severity infection, and mortality risks. The LD QMRA model may lead to risk based limits to supplement the current guidance on Legionella control in cooling towers, whirlpool spas and other potential exposure sources. The verification of QMRA for LD also suggests the techniques, given suitable animal model data, may be useful in quantifying human response to other airborne pathogens.

Effect of pipe corrosion scales on chlorine dioxide consumption in drinking water distribution systems

Previous studies showed that temperature and total organic carbon in drinking water would cause chlorine dioxide (ClO 2) loss in a water distribution system and affect the efficiency of ClO 2 for Legionella control. However, among the various causes of ClO 2 loss in a drinking water distribution system, the loss of disinfectant due to the reaction with corrosion scales has not been studied in detail. In this study, the corrosion scales from a galvanized iron pipe and a copper pipe that have been in service for more than 10 years were characterized by energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The impact of these corrosion scale materials on ClO 2 decay was investigated in de-ionized water at 25 and 45 °C in a batch reactor with floating glass cover. ClO 2 decay was also investigated in a specially designed reactor made from the iron and copper pipes to obtain more realistic reaction rate data. Goethite ( α-FeOOH) and magnetite (Fe 3O 4) were identified as the main components of iron corrosion scale. Cuprite (Cu 2O) was identified as the major component of copper corrosion scale. The reaction rate of ClO 2 with both iron and copper oxides followed a first-order kinetics. First-order decay rate constants for ClO 2 reactions with iron corrosion scales obtained from the used service pipe and in the iron pipe reactor itself ranged from 0.025 to 0.083 min −1. The decay rate constant for ClO 2 with Cu 2O powder and in the copper pipe reactor was much smaller and it ranged from 0.0052 to 0.0062 min −1. Based on these results, it can be concluded that the corrosion scale will cause much more significant ClO 2 loss in corroded iron pipes of the distribution system than the total organic carbon that may be present in finished water.

In vitro efficacy of copper and silver ions in eradicating Pseudomonas aeruginosa, Stenotrophomonas maltophilia and Acinetobacter baumannii: Implications for on-site disinfection for hospital infection control

Pseudomonas aeruginosa, Stenotrophomonas maltophilia and Acinetobacter baumannii are major opportunistic waterborne pathogens causing hospital-acquired infections. Copper–silver ionization has been shown to be effective in controlling Legionella colonization in hospital water systems. The objective was to determine the efficacy of copper and silver ions alone and in combination in eradicating P. aeruginosa, S. maltophilia and A. baumannii at the concentration applied to Legionella control. Kill curve experiments and mathematical modeling were conducted at copper and silver ion concentrations of 0.1, 0.2, 0.4, 0.8 and 0.01, 0.02, 0.04, 0.08 mg/L, respectively. The combinations of copper and silver ions were tested at concentrations of 0.2/0.02 and 0.4/0.04 mg/L, respectively. Initial organism concentration was ca. of 3×10 6 cfu/mL, and viability of the test organisms was assessed at predetermined time intervals. Samples (0.1 mL) withdrawn were mixed with 10 μL neutralizer solution immediately, serially diluted and plated in duplicate onto blood agar plates. The culture plates were incubated for 48 h at 37 °C and enumerated for the cfu (detection limit 10 cfu/mL). The results showed all copper ion concentrations tested (0.1–0.8 mg/L) achieved more than 99.999% reduction of P. aeruginosa which appears to be more susceptible to copper ions than S. maltophilia and A. baumannii. Silver ions concentration of 0.08 mg/L achieved more than 99.999% reduction of P. aeruginosa, S. maltophilia and A. baumannii in 6, 12 and 96 h, respectively. Combination of copper and silver ions exhibited a synergistic effect against P. aeruginosa and A. baumannii while the combination exhibited an antagonistic effect against S. maltophilia. Ionization may have a potential to eradicate P. aeruginosa, S. maltophilia and A. baumannii from hospital water systems.

A Cool Drink on a Hot Day – Hospital-Acquired Legionella Pneumonia

ISSUE: A proactive Legionella control program combining continuous disinfection of the water distribution system, environmental sampling and active case detection was established in a large urban hospital in the early 1990's. While cases of community-acquired disease are generally seen in the area during the rainy spring months, no patients had been identified with hospital acquired infection until Sept. 2005, after a particularly hot, dry summer.PROJECT: In order to prevent additional infections, all systems were immediately reviewed. Routine cultures of hospital sinks and showers had occasionally shown low levels of Legionella pneumophila in less than 30% of samples collected. There were no disruptions in the water supply and readings from the copper-silver ionization system were within range. Although the hospital's hot water supply is disinfected by the system, the cold water supply is not treated since the cooler water is not considered to be at increased risk for Legionella multiplication. After the case was identified, cultures were collected from additional water sources, including the new state of the art ice and water dispenser that served the patient unit. Maintenance personnel provided documentation that the unit was cleaned and sanitized as per manufacturer's instructions and provided the service manual for review.RESULTS: Cultures collected from the dispenser's water chute showed confluent growth of Legionella pneumophila serogroup 1. Isolates from the environment and patient submitted to a reference lab for Pulsed-Field Gel Electrophoresis (PFGE) had identical patterns. Periodic cleaning procedures in the manual stated that a chlorinated cleaning solution (200 ppm available chlorine) should be used, followed by a sanitizing solution (50 ppm). Since this sequence was reversed from our usual disinfection practices, the manufacturer of the recommended cleaner was contacted. The company was unaware that their product was mentioned and confirmed that these steps were incorrectly listed. Another factor leading to the disinfection failure was identified- maintenance personnel did not realize that the solutions were to be 75°F-125°F.LESSONS LEARNED: During the hot summer months, water coming in from the municipal water supply was reported to be unusually warm, theoretically allowing small numbers of Legionella in the water to multiply. While the preventative maintenance schedule was being followed according to the manufacturer's instructions, the incorrect dilution sequence and low temperature of the solution used potentially allowed the interior surfaces of the machine to develop a biofilm layer containing Legionella - a problem common in our hard water area. While we thought that our high-tech, proactive system was working wonderfully, all it took was a cool drink on a hot day to break our winning streak of Legionella prevention. And an unfortunate patient with a history of aspiration.

Isolation and characterization of Legionella spp. and Pseudomonas spp. from greenhouse misting systems

Greenhouse misting systems used for watering plants produce fine aerosols. They are a possible cause for bacterial infections. This study investigates the colonization of greenhouse misting systems with Legionella spp. and Pseudomonas spp. and evaluates a possible health hazard. Between June and September 2003, a total of 80 water samples were collected in 20 different greenhouse systems in Germany, each tested on two different occasions. Each time, water was drawn at a central tap and at the outlet of spray nozzles. Sampled greenhouses were used to cultivate various plants and trees for commercial, recreational or scientific reasons, some of them in tropical conditions. Legionella spp. were detected in 10% of the systems (two systems), but only in low numbers. On the contrary, Pseudomonas spp. were recovered from 70% of the greenhouse watering systems (14 systems), occasionally at counts greater than 10,000 CFU per 100 ml. A random amplified polymorphic DNA polymerase chain reaction typing method was used to demonstrate that each colonized greenhouse had one or several individual strains of Legionella and Pseudomonas that could not be detected in any other system. This study demonstrates that aerosolizing greenhouse watering systems may be contaminated with Legionella or Pseudomonas which under certain circumstances could become a potential source of infection for workers and visitors. The study results indicate that greenhouse misting systems should be included in Legionella and Pseudomonas monitoring and control programs.

P9.10 Legionella Control in a Hospital Water Supply System: Missing Sieves in Thermostatic Mixers Causing a Persisting Problem

P9.10 Legionella Control in a Hospital Water Supply System: Missing Sieves in Thermostatic Mixers Causing a Persisting Problem

Comparison of disinfectants for biofilm, protozoa and Legionella control

The aim of this study was to compare the efficiency of different disinfectants applicable to Legionella control in domestic water systems. A domestic water supply simulation unit that allowed simulation of real-world conditions was developed for this purpose. The system, consisting of seven identical rigs, was used to compare treatment efficiency under equivalent conditions of system design, materials, hydraulics, water quality, temperature and initial contamination. During the study, each of six loops received continuous application of one of the following disinfectants: chlorine, electro-chlorination, chlorine dioxide, monochloramine, ozone, or copper/silver. The seventh loop was used as a control and remained untreated. Performance evaluation of these disinfectants was based on their ability to reduce not only Legionella, but also protozoa and biofilms, which contribute to the establishment and dissemination of these bacteria in water systems, and their resistance to treatments. Regarding these criteria, chlorine dioxide and chlorine (as bleach or obtained by electro-chlorination) were the most effective treatments in this study. However, in comparison with chlorine, chlorine dioxide showed a longer residual activity in the system, which constituted an advantage in the perspective of an application to extensive pipework systems.

Legionella Control in Cooling Towers by Electrolytic Disinfection

The cooling towers of any industrial plant pose a large risk due to the existence of hazardous microorganisms, especially Legionellae. The electrolytic disinfection process has a wide applicability in the process industry. In this paper the results of an industrial case study are presented.

Legionnaires' disease in Europe 2000-2002.

Each year, countries that participate in the European Surveillance Scheme for Travel Associated Legionnaires' Disease (EWGLINET) are requested to complete a set of standardized reporting forms that provide epidemiological and microbiological information on the total number of cases (non-travel as well as travel-related cases) detected in their country. Trends at the national and aggregated European level have been analysed for 2000-2002. For this period, 10,322 cases of Legionnaires' disease were reported and national infection rates ranged from 0 to 34.1 cases per million population. A total of 189 outbreaks were associated with nosocomial infection, community exposure or travel. The upward trend in diagnosis through the urinary antigen detection test has resulted in a higher ascertainment of cases in many countries. However, the decline in diagnosis by culture of the organism is likely to severely hamper outbreak investigations in the future if fewer clinical isolates are available for matching with environmental isolates. This important data-set has been used for studying the effectiveness of surveillance and legionella control and prevention programmes within Europe.

Keeping Legionella out of water systems

Hospitals are often required to perform a supplemental disinfection of their water systems to protect individuals from hospital‐acquired Legionnaires' disease. The authors of this article recently studied one hospital where three cases of hospital‐acquired Legionnaires' disease were detected in less than two years. These cases were linked to Legionella colonization of the hospital's water system. Chlorine dioxide (ClO2) was considered a cost‐effective approach to disinfection given that ClO2 generators could treat the 23 buildings comprising the hospital complex from one central location. The authors evaluated the efficacy of maintaining a residual of 0.5 to 0.8 mg/L of ClO2 for Legionella control in the secondary distribution system of this 437‐bed hospital over a two‐year period. Monthly monitoring showed mean Legionella positivity at hot water outlets and cold building source water areas decreased from 23 to 12% and 9 to 0%, respectively (p&lt; 0.05). ClO2 residuals decreased with increasing distance from the application point and temperature. Mean ClO2 concentrations were lowest in hot water outlets (0.08 mg/L) followed by cold water outlets (0.33 mg/L) and reservoirs (0.68 mg/L). Complete eradication (0% positivity) of Legionella was achieved after 1.75 years, and no cases of Legionnaires' disease were reported during this time.

Hygienic quality of the water of public swimming pools--comments on a current German ordinance draft

In April 2002, a new draft regarding the quality of the water of public swimming pools in Germany was published. This draft was adapted to the new regulations for drinking water in respect of its structure and regulations. Microbiological tests for assessing the quality of bathing water are given priority. With regard to basic differences in facilities for drinking water and such for bath water and to legal aspects, many data (n = 14,425 data) on the practical experience of public health authorities are presented, obtained during the last few years. With regard to the data and in respect of the great delay between sampling and obtaining the results it is concluded that microbiological methods are inappropriate parameters for rapid assessment of the quality of bath water. Hence it is recommended to implement the evaluation of disinfection by chlorination including pH as an indicator for the quality of a bath water, parallel to the guidelines on technical standards. A high frequency of chlorination testing can markedly reduce the number of microbiological tests. Additionally, microbiological tests of the filtrate before disinfection by chlorination are recommended. This procedure has proved successful in legionella control.

The prevention and control of Legionella spp. (including Legionnaires' disease) in food factories

This article is an extended summary of the report prepared by the Process Water Subgroup of the European Hygienic Engineering & Design Group (EHEDG). It is the 23rd in the series of EHEDG summaries published in TIFS. Copies of the full report (EHEDG Doc. 24, August 2002) prepared by A.M. van Buren (Chairman), J.A. Milligan, H.M.J. van Eijk, J. O'Brien, S.D. Pannell, D. Lawrence, R. Hopman, W.G.J.M. van Tongeren, are available from CCFRA at pubs@camden.co.uk Information about EHEDG can be found on the website at www.ehedg.org It is strongly recommended that for application in the field, operators in the food industry should read the guidelines in its entirety, to ensure a holistic approach to legionella control.

Evaluación de un nuevo ensayo de ELISA (Bartels) para la detección de antígeno de Legionella pneumophila en orina

Detection of Legionella pneumophila soluble antigens allows rapid diagnosis of pneumonia caused by these bacteria. A new ELISA (Bartels) for antigenuria detection has recently been commercialized. We compared the new ELISA with another well-established ELISA (Binax). To evaluate ELISA-Bartels (Legionella Urinary Antigen, Intracel, Issaquah, Washington, United States), urine samples previously characterized by ELISA Binax (Legionella Urinary Antigen Enzyme Immunoassay Kit, Binax, Portland, Maine, United States) were used. Samples came from Legionella outbreaks (n = 48), from sporadic legionellosis (n = 38), and from children with viral pneumonia (n = 21). Samples from the External Quality Control of Legionella of the European Working Group on Legionella Infections (n = 102) were also tested. Of the samples analyzed, 109 were positive in ELISA-Binax, 2 were equivocal and 98 were negative. Samples showing equivocal results were excluded from the analysis. The sensitivity of ELISA-Bartels in comparison with that of ELISA-Binax was 98.2% (107/109) and specificity was 82.7% (81/98). In the 17 samples that were positive in ELISA-Bartels and negative in ELISA-Binax, 10 were positive in ELISA-Binax after concentration by selective ultrafiltration and 6 further cases showed serology indicating or compatible with recent Legionella infection and were thus classified as true positives. ELISA-Bartels showed good sensitivity and specificity. Sensitivity was even higher than that of ELISA-Binax. Thus, we consider it to be an appropriate method for diagnosis of Legionella pneumonia.

Discussion of “Monochloramine and Legionnaires' disease”

This paper discusses the hypothesis that monochloramine may be beneficial or control of Legionella in plumbing systems. Because monochloramine chlorine penetrates biofilms better than free chlorine, the hypothesis that chloramines are more effective in the biological niche of Legionella is biologically plausible. Investigators from the Centers for Disease Control and Prevention (CDC) presented a study in the September 2000 issue of Journal AWWA concluding that the use of monochloramine for disinfection of municipal water might prevent Legionnaires' disease. These authors suggested that 90 percent of hospital‐acquired outbreaks of Legionnaires' disease associated with drinking water might not have occurred if monochloramine had been used instead of free chlorine for residual disinfection.

Routine sampling and the control of Legionella spp. in cooling tower water systems.

Cooling water samples from 31 cooling tower systems were cultured for Legionella over a 16-week summer period. The selected systems were known to be colonized by Legionella. Mean Legionella counts and standard deviations were calculated and time series correlograms prepared for each system. The standard deviations of Legionella counts in all the systems were very large, indicating great variability in the systems over the time period. Time series analyses demonstrated that in the majority of cases there was no significant relationship between the Legionella counts in the cooling tower at time of collection and the culture result once it was available. In the majority of systems (25/28), culture results from Legionella samples taken from the same systems 2 weeks apart were not statistically related. The data suggest that determinations of health risks from cooling towers cannot be reliably based upon single or infrequent Legionella tests.

Silver/Copper ionization is effective for controlof legionella

SIR-As the manufacturer of the Tarn Pure ionization system used in the hospital discussed by Rohr et al. [1], I feel obliged to respond. The system was correctly installed by our own engineers and initially set to give the correct levels of silver and copper ions within the hot water circulating loops. The recommended levels for effective disinfection are 40 gg/L of silver and 400 /g/L of copper. Initially the effect was to kill the high levels of Legionella bacteria and to disrupt established biofilm in the water system. It appears that the output of our systems was reduced to comply with the maximum level normally allowed in Germany of 10 ,Lg/L of silver. No doubt due to absorption by debris, silver levels dropped to 5 ig/L for some time, and the copper levels only registered the same as the background level of copper before the system was activated. It should be noted that the initial, correct levels of treatment had a mediumto long-term effect even when the systems were running at a very low output. Therefore, we must conclude that the evaluation of Rohr et al. had no significant findings; it cannot be concluded that there was any build-up of resistance to the ionic treatment. The results obtained from our many installations in the United States, Europe and in the United Kingdom clearly indicate that TarnPure systems are effective when they are set to produce correct levels of silver and copper. The Health and Safety Executive (the regulatory body responsible for controlling all forms of hazards regarding the public at large in the United Kingdom) states that ionization is effective when silver levels are 20-40 tIg/L and copper levels are 400 tg/L, as we recommend [2; pg. 2]. We have installations that have been in continuous use for many years, and there is no evidence that resistance to the treatment has developed.