Effect of monochloramine disinfection of municipal drinking water on risk of nosocomial Legionnaires' disease

Legionella pneumophila associated with the protozoan Hartmannella vermiformis in a model multi-species biofilm has reduced susceptibility to disinfectants

Legionella pneumophila will infect biofilm-associated protozoa, and in this way might be protected from disinfectants in potable water systems. A base biofilm containing Pseudomonas aeruginosa, Klebsiella pneumoniae, and Flavobacterium spp. was grown on steel coupons in potable water prior to the addition of L. pneumophila and the protozoan H. vermiformis. After 7 d, coupons were removed and treated with 0.5 mgl(-1) free residual chlorine (FRC) or 0.5 mgl(-1) monochloramine (MCA) for 15, 60, or 180 min or 24 h. In a second experiment, only L. pneumophila and the base biofilm organisms were present but with an identical treatment protocol. Treatment of L. pneumophila for 180 min in a system without H. vermiformis resulted in log reductions of 2.07 and 2.11 for FRC and MCA, respectively. When H. vermiformis was present, however, the treatment resulted in log reductions of 0.67 and 0.81 for FRC and MCA, respectively. A similar pattern was observed for 15 and 60 min contact times. These results indicate that L. pneumophila was less susceptible to MCA or FRC when associated with biofilm-associated H. vermiformis in a model potable water biofilm.

Detection and identification of Legionella species from groundwaters

Legionellae are opportunistic bacterial pathogens causing Legionnaires' disease and Pontiac fever and are ubiquitous in surface waters and in infrastructure to contain or distribute water, including pipes, cooling towers, and whirlpool spas. Infection in community-acquired and nosocomial outbreaks is by exposure to contaminated aerosols. Little is known about the presence of legionellae in groundwater. This study used samples from various locations in the United States and Canada to determine if legionellae could be isolated from water and biofilms derived from groundwaters not known to be under the direct influence of surface water. Of the 114 total samples of water and biofilm tested, 29.1% and 28.2% were positive for Legionella by cultivation and polymerase chain reaction (PCR), respectively. Legionellae were found in both warm and colder groundwaters, with more isolates from samples incubated at 30 degrees C than the 35 degrees C conventional temperature for Legionella isolation. The concentration of Legionella found in the water samples ranged from 10(2) to 10(5) CFU/L and up to 1.2 x 10(2) CFU/cm(2) in the biofilm. The species of Legionella identified included both known pathogenic species and species that have not yet been identified as human pathogens. Millions of people in Canada, and around the world, rely on groundwater as their source for drinking. This study shows that legionellae are widespread in groundwater and have the potential to seed derived water supplies and biofilms in public distribution systems. This further widens the known sphere of Legionella colonization and the implications of its presence for public health.

Comparison of the efficacy of free residual chlorine and monochloramine against biofilms in model and full scale cooling towers

The presence of microbial cells on surfaces results in the formation of biofilms, which may also give rise to microbiologically influenced corrosion. Biofilms accumulate on all submerged industrial and environmental surfaces. The efficacy of disinfectants is usually evaluated using planktonic cultures, which often leads to an underestimate of the concentration required to control a biofilm. The aim of this study was to investigate the efficacy of monochloramine on biofilms developed in a cooling tower. The disinfectants selected for the study were commercial formulations recommended for controlling microbial growth in cooling towers. A cooling tower and a laboratory model recirculating water system were used as biofilm reactors. Although previous studies have evaluated the efficacy of free chlorine and monochloramine for controlling biofilm growth, there is a lack of published data concerning the use monochloramine in cooling towers. Stainless steel coupons were inserted in each tower basin for a period of 30 d before removal. Monochloramine and free chlorine were tested under identical conditions on mixed biofilms which had been allowed to grow on coupons. Monochloramine was found to be significantly more effective than free chlorine against cooling tower biofilms.

Risk of hospital-acquired legionnaires' disease in cities using monochloramine versus other water disinfectants

OBJECTIVE

To measure the association between the disinfection of municipal drinking water with monochloramine and the occurrence of hospital-acquired legionnaires' disease (LD).

SETTING

One hundred sixty-six U.S. hospitals.

DESIGN

Survey of 459 members of the Society for Healthcare Epidemiology of America (SHEA) for hospital features; endemic- and outbreak-related, hospital-acquired LD; the source of the hospital water supply; and the methods of disinfection used by the hospitals and municipal water treatment plants.

RESULTS

SHEA members representing 166 (36%) of 459 hospitals responded; 33 (20%) reported one or more episodes of hospital-acquired LD during the period from 1994 to 1998 and 23 (14%) reported an outbreak of hospital-acquired LD during the period from 1989 to 1998. Hospitals with an occurrence of hospital-acquired LD had a higher census (median, 319 vs 221; P = .03), more acute care beds (median, 500 vs 376; P = .04), and more intensive care unit beds (median, 42 vs 24; P = .009) than did other hospitals. They were also more likely to have a transplant service (74% vs 42%; P = .001) and to perform surveillance for hospital-acquired disease (92% vs 61%; P = .001). After adjustment for the presence of a transplant program and surveillance for legionnaires' disease, hospitals supplied with drinking water disinfected with monochloramine by municipal plants were less likely to have sporadic cases or outbreaks of hospital-acquired LD (odds ratio, 0.20; 95% confidence interval, 0.07 to 0.56) than were other hospitals.

CONCLUSION

Water disinfection with monochloramine by municipal water treatment plants significantly reduces the risk of hospital-acquired LD.

Ultraviolet light disinfection of hospital water for preventing nosocomial Legionella infection: a 13-year follow-up

BACKGROUND AND OBJECTIVE

CDC has estimated that 23% of Legionella infections are nosocomial. When a new hospital was being constructed and a substantial increase in transplantation was anticipated, an ultraviolet light apparatus was installed in the water main of the new building because 27% of water samples from taps in the old hospital contained Legionella. This study reports the rate of nosocomial Legionella infection and water contamination since opening the new hospital.

METHODS

Charts of all patients with positive Legionella cultures, direct immunofluorescent antibody (DFA), or urine antigen between April 1989 and November 2001 were reviewed. Frequencies of DFAs and urine antigens were obtained from the laboratory.

RESULTS

None of the 930 cultures of hospital water have been positive since moving into the new building. Fifty-three (0.02%) of 219,521 patients had a positive Legionella test; 41 had pneumonia (40 community acquired). One definite L. pneumophila pneumonia confirmed by culture and DFA in August 1994 was nosocomial (0.0005%) by dates. This patient was transferred after prolonged hospitalization in another country, was transplanted 11 days after admission, and developed symptoms 5 days after liver transplant. However, tap water from the patient's room did not grow Legionella. Seventeen (2.5%) of 670 urine antigens were positive for Legionella (none nosocomial). Thirty-three (1.2%) of 2,671 DFAs were positive, including 7 patients (21%) without evidence of pneumonia and 6 (18%) who had an alternative diagnosis.

CONCLUSION

Ultraviolet light usage was associated with negative water cultures and lack of clearly documented nosocomial Legionella infection for 13 years at this hospital.

The physiology and pharmacology of singlet oxygen

Reactive oxygen species (ROS) are generated by many different cells. Singlet oxygen (1O(2)) and a reaction product of it, excited carbonyls (C=O*), are important ROS. 1O(2) and C=O* are nonradicalic and emit light (one photon/molecule) when returning to ground state oxygen. Especially activated polymorphonuclear neutrophil granulocytes (PMN) produce large amounts of 1O(2). Via activation of the respiratory burst (NADPH oxidase and myeloperoxidase) they synthesize hypochlorite (NaOCl) and chloramines (in particular N-chlorotaurine). Chloramines are selective and stable chemical generators of 1O(2). In the human organism, 1O(2) is both a signal and a weapon with therapeutic potency against very different pathogens, such as microbes, virus, cancer cells and thrombi. Chloramines at blood concentrations between 1 and 2 mmol/L inactivate lipid enveloped virus and chloramines at blood concentrations below 0.5 mmol/L, i.e. at oxidant concentrations that do not affect thrombocytes or hemostasis factors, act antithrombotically by activation of the physiologic PMN mediated fibrinolysis; this thrombolysis is of selective nature, i.e. it does not impair the hemostasis system of the patient allowing the antithrombotic treatment in patients where the current risky thrombolytic treatment is contraindicated. The action of 1O(2) might be compared to the signaling and destroying gunfire of soldiers directed against bandits at night, resulting in an autorecruitment of the physiological inflammatory response. Chloramines (such as the mild and untoxic oxidant chloramine T (N-chloro-p-toluene-sulfonamide)) and their signaling and destroying reaction product 1O(2) might be promising new therapeutic agents against a multitude of up to now refractory diseases.

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).

Legionella and Legionnaires' disease: 25 years of investigation

There is still a low level of clinical awareness regarding Legionnaires' disease 25 years after it was first detected. The causative agents, legionellae, are freshwater bacteria with a fascinating ecology. These bacteria are intracellular pathogens of freshwater protozoa and utilize a similar mechanism to infect human phagocytic cells. There have been major advances in delineating the pathogenesis of legionellae through the identification of genes which allow the organism to bypass the endocytic pathways of both protozoan and human cells. Other bacteria that may share this novel infectious process are Coxiella burnetti and Brucella spp. More than 40 species and numerous serogroups of legionellae have been identified. Most diagnostic tests are directed at the species that causes most of the reported human cases of legionellosis, L. pneumophila serogroup 1. For this reason, information on the incidence of human respiratory disease attributable to other species and serogroups of legionellae is lacking. Improvements in diagnostic tests such as the urine antigen assay have inadvertently caused a decrease in the use of culture to detect infection, resulting in incomplete surveillance for legionellosis. Large, focal outbreaks of Legionnaires' disease continue to occur worldwide, and there is a critical need for surveillance for travel-related legionellosis in the United States. There is optimism that newly developed guidelines and water treatment practices can greatly reduce the incidence of this preventable illness.

Nosocomial legionellosis

Numerous reports of endemic legionellosis have been published within the past year. The scope has been expanded to longterm care facilities, nursing homes, rehabilitation centers, and pediatric hospitals. The institutional water supply has been the source in all reports and aspiration was explicitly linked as the mode of transmission in several reports. Discovery of a single case should not be considered as an isolated sporadic event, but instead indicative of unrecognized cases within that hospital. Copper-silver ionization has displaced hyperchlorination as the longterm disinfection modality of choice. Guidelines mandating the use of routine environmental cultures in hospital water supplies have been implemented in several American states and European countries.

An outbreak of Legionella micdadei pneumonia in transplant patients: evaluation, molecular epidemiology, and control

PURPOSE

To describe a nosocomial outbreak of Legionella micdadei pneumonia in transplant patients and to characterize the source of the outbreak and the control measures utilized.

SUBJECTS AND METHODS

We performed retrospective Legionella micdadei serologic testing to enhance case finding in transplant patients with pneumonia that lacked a documented microbial etiology, as well as prospective environmental surveillance of water sites and testing for Legionella in clinical specimens.

RESULTS

During a 3-month period, 12 cases of Legionella micdadei pneumonia were identified either by culture or serologic testing among 38 renal and cardiac transplant patients. Legionella micdadei isolates from hot water sources were found by pulsed-field gel electrophoresis to have a DNA banding pattern that was identical to the isolates from the first 3 culture-positive cases and from 2 cases that occurred 16 months later.

CONCLUSIONS

Hospitals caring for organ transplant recipients and other immunosuppressed patients must be aware of the possibility of environmental sources of outbreaks of Legionella infection. A first-line screen with the Legionella urine antigen test will identify Legionella pneumophila serogroup 1. However, specific cultures in outbreak situations should be considered to identify other Legionella pneumophila serotypes and the nonpneumophila Legionella species.

Hospital characteristics associated with colonization of water systems by Legionella and risk of nosocomial legionnaires' disease: a cohort study of 15 hospitals

OBJECTIVE

To investigate an increase in reports of legionnaires' disease by multiple hospitals in San Antonio, Texas, and to study risk factors for nosocomial transmission of legionnaires' disease and determinants for Legionella colonization of hospital hot-water systems.

SETTING

The 16 largest hospitals in the cities of San Antonio, Temple, and Austin, Texas.

DESIGN

Review of laboratory databases to identify patients with legionnaires' disease in the 3 years prior to the investigation and to determine the number of diagnostic tests for Legionella performed; measurement of hot-water temperature and chlorine concentration and culture of potable water for Legionella. Exact univariate calculations, Poisson regression, and linear regression were used to determine factors associated with water-system colonization and transmission of Legionella.

RESULTS

Twelve cases of nosocomial legionnaires' disease were identified; eight of these occurred in 1996. The rise in cases occurred shortly after physicians started requesting Legionella urinary antigen tests. Hospitals that frequently used Legionella urinary antigen tests tended to detect more cases of legionnaires' disease. Legionella was isolated from the water systems of 11 of 12 hospitals in San Antonio; the 12th had just experienced an outbreak of legionnaires' disease and had implemented control measures. Nosocomial legionellosis cases probably occurred in 5 hospitals. The number of nosocomial legionnaires' disease cases in each hospital correlated better with the proportion of water-system sites that tested positive for Legionella (P=.07) than with the concentration of Legionella bacteria in water samples (P=.23). Hospitals in municipalities where the water treatment plant used monochloramine as a residual disinfectant (n=4) and the hospital that had implemented control measures were Legionella-free. The hot-water systems of all other hospitals (n=11) were colonized with Legionella. These were all supplied with municipal drinking water that contained free chlorine as a residual disinfectant. In these contaminated hospitals, the proportion of sites testing positive was inversely correlated with free residual chlorine concentration (P=.01). In all hospitals, hot-water temperatures were too low to inhibit Legionella growth.

CONCLUSIONS

The increase in reporting of nosocomial legionnaires' disease was attributable to increased use of urinary antigen tests; prior cases may have gone unrecognized. Risk of legionnaires' disease in hospital patients was better predicted by the proportion of water-system sites testing positive for Legionella than by the measured concentration of Legionella bacteria. Use of monochloramine by municipalities for residual drinking water disinfection may help prevent legionnaires' disease.

Lessons from recent nosocomial epidemics

This review describes important examples of recent nosocomial infection epidemics. Current trends suggest that emerging problems in nosocomial infections include increased nosocomial epidemics in out-of-hospital settings, contamination of medical devices and products, and antimicrobial resistance. Increased attention should be focused on outbreak investigations in these areas.

Legionella: from environmental habitats to disease pathology, detection and control

Studies on Legionella show a continuum from environment to human disease. Legionellosis is caused by Legionella species acquired from environmental sources, principally water sources such as cooling towers, where Legionella grows intracellularly in protozoa within biofilms. Aquatic biofilms, which are widespread not only in nature, but also in medical and dental devices, are ecological niches in which Legionella survives and proliferates and the ultimate sources to which outbreaks of legionellosis can be traced. Invasion and intracellular replication of L. pneumophila within protozoa in the environment play a major role in the transmission of Legionnaires' disease. Protozoa provide the habitats for the environmental survival and reproduction of Legionella species. L. pneumophila proliferates intracellularly in various species of protozoa within vacuoles studded with ribosomes, as it also does within macrophages. Growth within protozoa enhances the environmental survival capability and the pathogenicity (virulence) of Legionella. The growth requirements of Legionella, the ability of Legionella to enter a viable non-culturable state, the association of Legionella with protozoa and the occurrence of Legionella within biofilms complicates the detection of Legionella and epidemiological investigations of legionellosis. Polymerase chain reaction (PCR) methods have been developed for the molecular detection of Legionella and used in environmental and epidemiological studies. Various physical and chemical disinfection methods have been developed to eliminate Legionella from environmental sources, but gaining control of Legionella in environmental waters, where they are protected from disinfection by growing within protozoa and biofilms, remains a challenge, and one that must be overcome in order to eliminate sporadic outbreaks of legionellosis.