Heat eradication measures for control of nosocomial Legionnaires' disease. Implementation, education, and cost analysis

Peracetic Acid in the Disinfection of a Hospital Water System Contaminated With Legionella Species

Objective:

To assess the efficacy of an alternative disinfection method for hospital water distribution systems contaminated with Legionella.

Methods:

Disinfection with peracetic acid was performed in a small hospital contaminated with L. pneumophila serotype 1. The disinfectant was used at concentrations of 50 ppm (first three surveillance phases) and 1,000 ppm (fourth surveillance phase) for 30 minutes.

Results:

Environmental monitoring revealed that disinfection was maintained 1 week after treatment; however, levels of recontamination surpassing baseline values were detected after approximately 1 month. Comparison of water temperatures measured at the distal outlets showed a statistically significant association between temperature and bacterial load. The circulating water temperature was found to be lower in the two wards farthest away from the hot water production plant than in other wards. It was thought that the lower water temperature in the two wards promoted the bacterial growth even after disinfection.

Conclusion:

Peracetic acid may be useful in emergency situations, but does not provide definitive protection even if used monthly.

Modelling characteristics to predict Legionella contamination risk - Surveillance of drinking water plumbing systems and identification of risk areas

For the surveillance of drinking water plumbing systems (DWPS) and the identification of risk factors, there is a need for an early estimation of the risk of Legionella contamination within a building, using efficient and assessable parameters to estimate hazards and to prioritize risks. The precision, accuracy and effectiveness of ways of estimating the risk of higher Legionella numbers (temperature, stagnation, pipe materials, etc.) have only rarely been empirically assessed in practice, although there is a broad consensus about the impact of these risk factors. We collected n = 807 drinking water samples from 9 buildings which had had Legionella spp. occurrences of >100 CFU/100mL within the last 12 months, and tested for Legionella spp., L. pneumophila, HPC 20°C and 36°C (culture-based). Each building was sampled for 6 months under standard operating conditions in the DWPS. We discovered high variability (up to 4 log(10) steps) in the presence of Legionella spp. (CFU/100 mL) within all buildings over a half year period as well as over the course of a day. Occurrences were significantly correlated with temperature, pipe length measures, and stagnation. Logistic regression modelling revealed three parameters (temperature after flushing until no significant changes in temperatures can be obtained, stagnation (low withdrawal, qualitatively assessed), pipe length proportion) to be the best predictors of Legionella contamination (>100 CFU/100 mL) at single outlets (precision = 66.7%; accuracy = 72.1%; F(0.5) score = 0.59).

Field testing hot water temperature reduction as an energy-saving measure--does the Legionella presence change in a clinic's plumbing system?

Legionella spp. represent a significant health risk for humans. To ensure hygienically safe drinking water, technical guidelines recommend a central potable water hot (PWH) supply temperature of at least 60°C at the calorifier. In a clinic building we monitored whether slightly lowered temperatures in the PWH system led to a systemic change in the growth of these pathogens. In four separate phases we tested different scenarios concerning PWH supply temperatures and disinfection with chlorine dioxide (ClO2). In each phase, we took 5 sets of samples at 17 representative sampling points in the building's drinking water plumbing system. In total we collected 476 samples from the PWH system. All samples were tested (culture-based) for Legionella spp. and serogroups. Additionally, quantitative parameters at each sampling point were collected, which could possibly be associated with the presence of Legionella spp. (Pseudomonas aeruginsoa, heterotrophic plate count at 20°C and 36°C, temperatures, time until constant temperatures were reached, and chlorine dioxide concentration). The presence of Legionella spp. showed no significant reactions after reducing the PWH supply temperature from 63°C to 60°C and 57°C, as long as disinfection with ClO2 was maintained. After omitting the disinfectant, the PWH system showed statistically significant growth rates at 57°C. PWH temperatures which are permanently lowered to less than recommended values should be carefully accompanied by frequent testing, a thorough evaluation of the building's drinking water plumbing system, and hygiene expertise.

Controlling Legionella in hospital drinking water: an evidence-based review of disinfection methods

Hospital-acquired Legionnaires' disease is directly linked to the presence of Legionella in hospital drinking water. Disinfecting the drinking water system is an effective preventive measure. The efficacy of any disinfection measures should be validated in a stepwise fashion from laboratory assessment to a controlled multiple-hospital evaluation over a prolonged period of time. In this review, we evaluate systemic disinfection methods (copper-silver ionization, chlorine dioxide, monochloramine, ultraviolet light, and hyperchlorination), a focal disinfection method (point-of-use filtration), and short-term disinfection methods in outbreak situations (superheat-and-flush with or without hyperchlorination). The infection control practitioner should take the lead in selection of the disinfection system and the vendor. Formal appraisals by other hospitals with experience of the system under consideration is indicated. Routine performance of surveillance cultures of drinking water to detect Legionella and monitoring of disinfectant concentrations are necessary to ensure long-term efficacy.

Legionella--every infection preventionist's dream--or is it?

Legionella is an underreported disease challenge within the hospital setting. In order to combat Legionella during times of construction and renovation, infection preventionists must become construction experts. The infection preventionist must be able to plan for potential waterborne disease outbreaks and protect the hospital staff, patients and visitors from waterborne pathogens. Legionella's history, signs and symptoms, diagnostic testing and treatment will be discussed. The hospital's convening of a multidisciplinary Legionella task force to work cohesively to develop a waterborne pathogens plan will also be discussed. This article was written from the perspective of the infection preventionist and employee health nurse at the time of the Legionella outbreak at their hospital.

Viability PCR, a culture-independent method for rapid and selective quantification of viable Legionella pneumophila cells in environmental water samples

PCR-based methods have been developed to rapidly screen for Legionella pneumophila in water as an alternative to time-consuming culture techniques. However, these methods fail to discriminate between live and dead bacteria. Here, we report a viability assay (viability PCR [v-PCR]) for L. pneumophila that combines ethidium monoazide bromide with quantitative real-time PCR (qPCR). The ability of v-PCR to differentiate viable from nonviable L. pneumophila cells was confirmed with permeabilizing agents, toluene, or isopropanol. v-PCR suppressed more than 99.9% of the L. pneumophila PCR signal in nonviable cultures and was able to discriminate viable cells in mixed samples. A wide range of physiological states, from culturable to dead cells, was observed with 64 domestic hot-water samples after simultaneous quantification of L. pneumophila cells by v-PCR, conventional qPCR, and culture methods. v-PCR counts were equal to or higher than those obtained by culture and lower than or equal to conventional qPCR counts. v-PCR was used to successfully monitor in vitro the disinfection efficacy of heating to 70 degrees C and glutaraldehyde and chlorine curative treatments. The v-PCR method appears to be a promising and rapid technique for enumerating L. pneumophila bacteria in water and, in comparison with conventional qPCR techniques used to monitor Legionella, has the advantage of selectively amplifying only viable cells.

Abbreviated duration of superheat-and-flush and disinfection of taps for Legionella disinfection: lessons learned from failure

One medical center in southern Taiwan faced an outbreak of nosocomial Legionnaires' disease; a total of 81 suspected cases were detected during an 8-month period. Baseline environmental surveillance showed that 80% of the distal sites in intensive care units (ICUs) were positive for Legionella pneumophila. Superheat-and-flush was selected for hospital water supply disinfection because it required no special equipment, and it can be initiated expeditiously. We conducted 2 episodes of superheat-and-flush based on the published recommendations from the Department of Health, Taiwan; US Centers for Disease Control and Prevention; and American Society of Heating, Refrigerating, and Air-Conditioning Engineers. Both flushes failed to control colonization of Legionella in the hospital water supply. The rate of distal sites positive for Legionella in wards and ICUs was 14% and 66%, respectively, 10 days after the second flush. The effect of replacement of faucets and showerheads in ICUs appeared to be insignificant in colonization of Legionella. The application of superheat-and-flush for flush duration of 5 minutes was ineffective. Superheat-and-flush may not be economic for a large medical center because it could be costly and labor intensive.

Use of terminal tap water filter systems for prevention of nosocomial legionellosis

Hospital water supplies often contain Legionella spp. and represent a potential source of nosocomial infection, especially for immunocompromised patients or those in intensive care units. Therefore, pathogen-free water should be provided for such high-risk patients. Surveillance of splash water was performed in high-risk patient care areas at Berlin Charité-University Medicine (506 samples) and Medical School Hannover (767 samples) to investigate the ability to provide water that was free from Legionella spp. by the use of disposable, terminal tap water filter systems with non-impregnated, as well as impregnated, filters with prolonged usage intervals. Twenty (Berlin) and 32 (Hannover) water outlets were provided with disposable filters with a pore size of 0.2 microm. Testing of unfiltered tap water revealed growth of Legionella spp. in 53 of 210 (Berlin) and 30 of 32 (Hannover) samples. Non-impregnated, terminal, disposable water filters at taps used for high-risk patient care led to water free from Legionella spp. in 154 of 155 (99.4%) samples after three to four days and in 137 of 141 (97.2%) samples after six to seven days. When testing a new impregnated filter, 255 of 256 (99.6%) samples remained free from Legionella spp. after continuous use for seven days, as recommended by the manufacturers, and also after 10 days. Samples that were positive for Legionella spp. contained 1-4 cfu/mL. We believe that an impregnated filter system is suitable for the prevention of nosocomial Legionellosis in high-risk patient care areas.

Reusable terminal tap water filters for nosocomial legionellosis prevention

Hospital water supplies often contain Legionella spp. and therefore represent a source of nosocomial infection especially for immunocompromised patients in intensive care or organ transplant units. Therefore, pathogen-free water should be provided for the care of these patients. Approaches of long-term Legionella spp. eradication from the plumbing system are rarely successful. Exposition prophylaxis might be another reasonable approach in high-risk patient care. To investigate the ability to provide water free of Legionella spp. with reusable water filters, a surveillance of splash water samples was performed. After determining the burden of Legionella spp. in the plumbing system of a paediatric oncological ward by ten unfiltered splash water samples, ten designated water taps were provided with terminal tap water filters that could be reprocessed by thermal disinfection. A further 129 samples were taken after a usage interval of 7 days and 10 more samples after a usage interval of 21 days before reprocessing the filters. All samples were checked for growth of Legionella spp. as well as other pathogenic bacteria. A total germ count of all samples was also performed. Half of the unfiltered splash water samples revealed growth of Legionella spp. All filtered water samples remained free of Legionella. Total germ count did not increase before a usage interval of 7 days. We believe the water filters tested are suitable for prevention of nosocomial legionellosis when reprocessed after 7 days as recommended by the manufacturer. To avoid retrograde contamination of filters, education of staff and patients in handling these devices is mandatory.

Hospital-acquired Legionnaires' disease: new developments

PURPOSE OF REVIEW

Hospital-acquired Legionnaires' disease is being increasingly discovered with the advent of rapid diagnostic techniques. This review examines both the clinical and political aspects of this important problem.

RECENT FINDINGS

New sources are being recognized, including the water supply of pediatric hospitals, long-term care facilities, and rehabilitation centers. Concern by the public, unfavorable publicity and litigation are now emerging as hospital-acquired Legionnaires' disease is coming under scrutiny by the lay media.

SUMMARY

Pro-active approaches to environmental detection and disinfection of hospital water systems are being demanded by public officials in place of the passive approach favored by many public health agencies.

Literature review--efficacy of various disinfectants against Legionella in water systems

There have been reported outbreaks of Legionnaires' disease at hospitals and industrial facilities, which prompted the development of various preventive measures. For example, Ford has been developing and implementing such a measure at its facilities worldwide to provide technical guidance for controlling Legionella in water systems. One of the key issues for implementing the measure is the selection of a disinfectant(s) and optimum conditions for its use. Therefore, available publications on various disinfectants and disinfection processes used for the inactivation of Legionella bacteria were reviewed. Two disinfection methods were reviewed: chemical and thermal. For chemical methods, disinfectants used were metal ions (copper and silver), oxidizing agents (halogen containing compounds [chlorine, bromine, iodine, chlorine dioxide, chloramines, and halogenated hydantoins], ozone, and hydrogen peroxide), non-oxidizing agents (heterocyclic ketones, guanidines, thiocarbamates, aldehydes, amines, thiocyanates, organo-tin compounds, halogenated amides, and halogenated glycols), and UV light. In general, oxidizing disinfectants were found to be more effective than non-oxidizing ones. Among oxidizing agents, chlorine is known to be effective and widely used. Among non-oxidizing agents, 2,2-dibromo-3-nitropropionamide appears to be the most effective followed by glutaraldehyde. Isothiazolin (known as Kathon), polyhexamethylene biguanide, and 2-bromo-2-nitropropionamide (known as Bronopol) were found to be less effective than glutaraldehyde. Thermal disinfection is effective at > 60 degrees C (140 degrees F).

A simple method for the eradication of Legionella pneumophila from potable water systems

In this paper we describe a simple method, noncorrosive to pipes, for the eradication of Legionella pneumophila from potable water systems. This method is based on the systematic purging of the pipe networks with cold water containing 1-1.5 mg residual chlorine/L. In the hot water system, a new pipe bypassing the water heater was installed, whereas in the air conditioning system, the circuit is purged with water from the tap water system. The feasibility of this method was studied in two hotels in which the presence of Legionella was detected despite treatment of the water by the hyperchlorination method. The evolution of the presence of Legionella was studied by culture and polymerase chain reaction. Eighty samples from hotel A and sixty-seven samples from hotel B were analyzed during the time that the eradication method was applied. Our results showed that this method permitted the effective elimination of L. pneumophila after 5 months in hotel A and 7 months in hotel B.

Nosocomial legionnaires disease in a children's hospital

Between August 1982 and December 1985, seven patients at a children's hospital developed hospital-acquired pneumonia caused by Legionella pneumophila. Demographic data included the following: mean age 12.3 years (range 9 months to 20.5 years); male/female ratio 5:2; all patients were white. Some previously identified risk factors present in our patients included high-dose corticosteroid therapy (five patients), other immunosuppressive therapy (four), and chronic lung (five) or kidney (three) disease. Symptoms and signs included rapid onset, fever, cough, pleuritic chest pain, dyspnea, abdominal pain, diarrhea, and headache. Rhinitis, myalgia, and neurologic abnormalities were not noted. Chest roentgenograms revealed single-lobe consolidation in three patients, diffuse bilateral alveolar infiltrates in three, and pleural effusion in three. All patients were treated with erythromycin; three patients also received rifampin. Tracheal intubation and mechanical ventilation were required by four patients. Six patients improved after therapy. One child died of persistent lung disease 1 month after the onset of legionnaires disease. L. pneumophila was isolated from potable water in the hospital. Aerosol equipment cleansed with tap water and the showers were implicated as means of exposure by patients to contaminated potable water. No new nosocomial cases were seen after immunocompromised children were prohibited from taking showers, and sterile water was used to cleanse equipment for administering aerosol medications.

Routine culturing for Legionella in the hospital environment may be a good idea: a three-hospital prospective study

The source for nosocomial Legionnaires' disease is the water distribution system. However, the implications for legionella contamination in a hospital without known Legionnaires' disease is unclear. Therefore, culturing for Legionella pneumophila in the environment has not been routinely recommended. The authors conducted a prospective pneumonia study in three hospitals, none of which was known to have a major problem with endemic legionellosis. The water system of Hospital 1 was colonized with L. pneumophila, serogroup 1; Hospital 2 was colonized by L. pneumophila, serogroup 5 (which is rarely associated with disease); Hospital 3 was essentially free of L. pneumophila. Sputum culture on selective legionella media, direct fluorescent antibody testing, and serology were performed for all nosocomial pneumonias regardless of clinical impression. At the end of the study the incidence of nosocomial legionnaires' disease was found to be 9%, 0%, and 0% in Hospitals 1, 2, and found to be 9%, 0%, and 0% in Hospitals 1, 2, and 3, respectively. In Hospital 1, monoclonal antibody subtyping confirmed that the patient isolates were identical to the environmental isolates. The authors conclude that environmental culturing, despite the absence of known Legionnaires' disease, is useful. Positive cultures from the hospital water supply would mandate the introduction of legionella testing into the laboratory and stimulate physicians to consider Legionnaires' disease when encountering nosocomial pneumonias.

Legionnaires' disease: an emerging surgical problem

Legionnaires' disease is an important, although often overlooked, complication in the patient postoperatively. Up to 50% of all nosocomial legionellosis in the hospitals reviewed was found in surgical patients. Patients undergoing a transplant procedure are at highest risk, but occurrence is common in the surgical patient undergoing general anesthesia, endotracheal intubation, or both. Aerosolization, aspiration, and direct instillation of contaminated water during manipulation of the respiratory tract are likely mechanisms of transmission. The usual clinical presentation is that of a nonspecific pneumonia. Specialized laboratory techniques including selective culture media, direct fluorescent antibody stains, and serological detection of antibodies are necessary for accurate diagnosis. If these tests are not routinely available, Legionnaires' disease may remain undiagnosed. Environmental surveillance of the hospital water distribution system is advisable for hospitals with a large surgical case load. If transplantation is performed, such surveillance is mandatory.

Comparative assessment of chlorine, heat, ozone, and UV light for killing Legionella pneumophila within a model plumbing system

Nosocomial Legionnaires disease can be acquired by exposure to the organism from the hospital water distribution system. As a result, many hospitals have instituted eradication procedures, including hypercholorination and thermal eradication. We compared the efficacy of ozonation, UV light, hyperchlorination, and heat eradication using a model plumbing system constructed of copper piping, brass spigots, Plexiglas reservoir, electric hot water tank, and a pump. Legionella pneumophila was added to the system at 10(7) CFU/ml. Each method was tested under three conditions; (i) nonturbid water at 25 degrees C, (ii) turbid water at 25 degrees C, and (iii) nonturbid water at 43 degrees C. UV light and heat killed L. pneumophila most rapidly and required minimal maintenance. Both UV light and heat (60 degrees C) produced a 5 log kill in less than 1 h. In contrast, both chlorine and ozone required 5 h of exposure to produce a 5 log decrease. Neither turbidity nor the higher temperature of 43 degrees C impaired the efficacy of any of the disinfectant methods. Surprisingly, higher temperature enhanced the disinfecting efficacy of chlorine. However, higher temperature accelerated the decomposition of the chlorine residual such that an additional 120% volume of chlorine was required. All four methods proved efficacious in eradicating L. pneumophila from a model plumbing system.

Are health care workers at risk for infection during an outbreak of nosocomial Legionnaires' disease?

We studied data from 500 health care workers to answer the question: Are health care workers at risk for infection during an outbreak of nosocomial Legionnaires' disease? These workers were employed at a hospital where eight cases of nosocomial Legionella pneumophila serogroup 1 pneumonia occurred over a 4-week period. The source was potable water. Acute-phase blood samples were collected on the day the water supply was decontaminated, convalescent samples were collected 4 to 6 weeks later from 373 subjects, and a single serum sample was obtained from an additional 127 subjects. Antibody titers to L. pneumophila were determined by an indirect immunofluorescent antibody (IFA) technique and by a microagglutination assay with the epidemic strain as the test antigen. Subjects who had an IFA titer of greater than or equal to 1:256 were retested with an anti-human IgM conjugate. None of the 373 health care workers had a fourfold rise in antibody titer. The geometric mean antibody titer of 73.8 for the 500 health care workers was significantly higher than that of 68.1 for 976 blood donors (p less than 0.01). Only 2.4% had recent infection as evidenced by a microagglutination test, despite the fact that 84% were susceptible. We conclude that in the setting of a short-term outbreak of Legionnaires' disease caused by contaminated potable water the risk of infection among health care workers is low: 2.4% or less.

Potential in-hospital modes of transmission of Legionella pneumophila. Demonstration experiments for dissemination by showers, humidifiers, and rinsing of ventilation bag apparatus

The mode of transmission of nosocomial legionellosis remains uncertain. Aerosolization of Legionella pneumophila by showers, humidifiers, and respiratory equipment rinsed in tap water was evaluated using plate-settling culture and air aspirator methods. All protocols simulated the actual hospital setting including use of humidifier equipment used in hospital patient rooms and water from faucets and showerheads in hospitals with nosocomial Legionnaires' disease. Protocols for humidifier and shower experiments mimicked the procedure actually used in hospitals by health care personnel. Showering failed to produce aerosols of L. pneumophila; however, portable humidifiers readily generated aerosols of L. pneumophila that disseminated throughout a two-bed patient room. Intensity of aerosolization directly correlated with the degree of L. pneumophila contamination of the tap water used to fill the humidifier. Rinsing of ventilation bag apparatus with tap water led to isolation of L. pneumophila from culture plates after the ventilation bags were squeezed. Thus, L. pneumophila could be aerosolized or directly instilled into a patient's bronchial tree following routine measures for cleaning ventilation bag apparatus with tap water. On the basis of these results, the use of humidifiers filled with tap water has been discontinued and sterile water is recommended for rinsing ventilation bag apparatus and tubing.

Nosocomial legionellosis in surgical patients with head-and-neck cancer: implications for epidemiological reservoir and mode of transmission

A prospective pneumonia study was conducted simultaneously on head-and-neck surgery wards at two hospitals over 2 years; one hospital had a water supply contaminated with Legionella pneumophila but no record of having had a case of legionella pneumonia, and the other had just decontaminated its water supply because of known endemic nosocomial legionellosis. Special laboratory tests for legionella were done on all cases of nosocomial pneumonia irrespective of clinical impression. Over the first 18 months, the rate of nosocomial legionellosis was 30% at the first hospital and 0% at the second. Patients who underwent laryngectomy did not acquire the disease. Hyperchlorination at the first hospital was followed by a fall (p less than 0.01) in legionella pneumonias. Thus legionella pneumonias can be overlooked if special laboratory tests are not applied routinely, and surgical patients with head-and-neck cancer may be at high risk of nosocomial legionellosis because of the potential for pulmonary aspiration of contaminated water or orophyaryngeal microflora and/or frequent manipulation of the respiratory tract. This study demonstrates the benefits of examining the environment for legionella despite the absence of documented disease.

Isolation of Legionella pneumophila from the cold water of hospital ice machines: implications for origin and transmission of the organism

Although the mode of transmission of L. pneumophila is as yet unclear, the hot water distribution system has been shown to be the reservoir for Legionella within the hospital environment. In this report we identify a previously unrecognized reservoir for L. pneumophila within the hospital environment, ie, the cold water dispensers of hospital ice machines. The cold water dispensers of 14 ice machines were cultured monthly over a 1-year period. Positive cultures were obtained from 8 of 14 dispensers, yielding from 1 to 300 CFU/plate. We were able to link the positivity of these cold water sites to the incoming cold water supply by recovering L. pneumophila from the cold water storage tank, which is directly supplied by the incoming municipal water line. This was accomplished by a novel enrichment experiment designed to duplicate the conditions (temperature, sediment, stagnation, and continuous seeding) of the hot water system. Our data indicate that significant contamination of cold water outlets with L. pneumophila can occur. Although no epidemiologic link to disease was made, the fact that the primary source of a patient's drinking water is from the ice machines warrants further investigation of these water sources as possible reservoirs.