Risk factors for contamination of domestic hot water systems by legionellae.
01 Aug 1991-Applied and Environmental Microbiology (American Society for Microbiology)-Vol. 57, Iss: 8, pp 2360-2367
TL;DR: To assess risk factors associated with the contamination of the domestic environment by legionellae, 211 houses in the Quebec City area were randomly selected and water samples were collected from the hot water tank, the shower heads, and the most frequently used faucet.
Abstract: To assess risk factors associated with the contamination of the domestic environment by legionellae, 211 houses in the Quebec City area were randomly selected and water samples were collected from the hot water tank, the shower heads, and the most frequently used faucet. After centrifugation, concentrated samples were seeded in triplicate on BCYE and GPV media. Data on the characteristics of the hot water system and plumbing in the house and on the personal habits of the occupants were collected for each house. Among these 211 houses, hot water was provided by either an oil or gas heater in 33 and by an electric heater in 178. Legionellae were isolated from none of the samples from houses with oil or gas heaters and from 39% (69 of 178) of those with electric water heaters (P less than 0.0001). This association remained highly significant after control for water temperature and other variables in a stratified analysis. In the 178 houses with an electric heater, 12% of the faucets, 15% of the shower heads, and 37% of the water heaters were contaminated. Legionella pneumophila serogroups 2 and 4 were the most frequently isolated strains. Logistic regression showed that factors associated with electric water heater contamination were (i) location of the house in older districts of the city (P less than 0.0001), (ii) old age of the water heater (P = 0.003), and (iii) low water temperature (P = 0.05). Contamination of the water heater was the only factor significantly associated with the contamination of peripheral outlets (P less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)
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TL;DR: It is concluded that showerheads may present a significant potential exposure to aerosolized microbes, including documented opportunistic pathogens, and the health risk associated with showerhead microbiota needs investigation in persons with compromised immune or pulmonary systems.
Abstract: The environments we humans encounter daily are sources of exposure to diverse microbial communities, some of potential concern to human health. In this study, we used culture-independent technology to investigate the microbial composition of biofilms inside showerheads as ecological assemblages in the human indoor environment. Showers are an important interface for human interaction with microbes through inhalation of aerosols, and showerhead waters have been implicated in disease. Although opportunistic pathogens commonly are cultured from shower facilities, there is little knowledge of either their prevalence or the nature of other microorganisms that may be delivered during shower usage. To determine the composition of showerhead biofilms and waters, we analyzed rRNA gene sequences from 45 showerhead sites around the United States. We find that variable and complex, but specific, microbial assemblages occur inside showerheads. Particularly striking was the finding that sequences representative of non-tuberculous mycobacteria (NTM) and other opportunistic human pathogens are enriched to high levels in many showerhead biofilms, >100-fold above background water contents. We conclude that showerheads may present a significant potential exposure to aerosolized microbes, including documented opportunistic pathogens. The health risk associated with showerhead microbiota needs investigation in persons with compromised immune or pulmonary systems.
490 citations
Cites background from "Risk factors for contamination of d..."
...Previous microbiological studies of showerhead biofilms have used culture methodology to detect and identify microbes, and have focused primarily on Legionella pneumophilia (7, 8, 9) and Mycobacterium avium (10–12)....
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TL;DR: Available publications on various disinfectants and disinfection processes used for the inactivation of Legionella bacteria were reviewed and oxidizing disinfectants were found to be more effective than non-oxidizing ones.
374 citations
TL;DR: To determine whether plumbing could be a source of nontuberculous mycobacteria (NTM) infection, during 2007–2009 I isolated NTM from samples from household water systems of NTM patients, finding households with water from public or private water systems serving multiple households were more likely to have NTM.
Abstract: To determine whether plumbing could be a source of nontuberculous mycobacteria (NTM) infection, during 2007-2009 I isolated NTM from samples from household water systems of NTM patients. Samples from 22/37 (59%) households and 109/394 (28%) total samples yielded NTM. Seventeen (46%) of the 37 households yielded ≥1 Mycobacterium spp. isolate of the same species as that found in the patient; in 7 of those households, the patient isolate and 1 plumbing isolate exhibited the same repetitive sequence-based PCR DNA fingerprint. Households with water heater temperatures ≤125 degrees C (≤50 degrees C) were significantly more likely to harbor NTM compared with households with hot water temperatures ≥130 degrees F (≥55 degrees C) (p = 0.0107). Although households with water from public or private water systems serving multiple households were more likely to have NTM (19/27, 70%) compared with households with a well providing water to only 1 household (5/12, 42%), that difference was not significant (p = 0.1532).
281 citations
TL;DR: The evidence suggests that specific members of HPC bacteria found in drinking water may be causative agents of both hospital- and community-acquired infections and drinking water could be a source of infection for some of these bacteria.
Abstract: Concern has been generated in the drinking water industry regarding the health effects of heterotrophic plate count (HPC) bacteria that are found in tap water, bottled water, and other sources of potable water. Heterotrophic bacteria are those that require organic carbon rather than carbon dioxide as a carbon source. All human bacterial pathogens are heterotrophic. The U.S. Environmental Protection Agency (EPA) has suggested that the heterotrophic bacterial counts in drinking water should not exceed 500 colony-forming units (CFU) mL-1, primarily because of the interference of coliform detection (USEPA 1989). Higher numbers are often the result of bacterial regrowth, particularly in distribution systems (Geldreich 1986; Olson 1982) and in water treatment devices (Geldreich et al. 1985; Payment 1989; Reasoner et al. 1987; Snyder et al. 1995). Some authors have expressed concern regarding the public health risk of some of these HPC bacteria (LeChevallier et al. 1985; Lye and Dufour 1991; McFeters et al. 1986; Payment et al. 1988).
237 citations
TL;DR: Legionella species and serogroups were differently distributed according to heater type, water temperature, and free chlorine, suggesting that Legionella strains may have a different sensibility and resistance to environmental factors and different ecologic niches.
Abstract: We investigated Legionella and Pseudomonas contamination of hot water in a cross-sectional multicentric survey in Italy. Chemical parameters (hardness, free chlorine, and trace elements) were determined. Legionella spp. were detected in 33 (22.6%) and Pseudomonas spp. in 56 (38.4%) of 146 samples. Some factors associated with Legionella contamination were heater type, tank distance and capacity, water plant age, and mineral content. Pseudomonas presence was influenced by water source, hardness, free chlorine, and temperature. Legionella contamination was associated with a centralized heater, distance from the heater point >10 m, and a water plant >10 years old. Furthermore, zinc levels of 50 microg/L appeared to be protective against Legionella colonization [corrected]. Legionella species and serogroups were differently distributed according to heater type, water temperature, and free chlorine, suggesting that Legionella strains may have a different sensibility and resistance to environmental factors and different ecologic niches.
206 citations
References
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Book•
01 Jan 1989
TL;DR: Hosmer and Lemeshow as discussed by the authors provide an accessible introduction to the logistic regression model while incorporating advances of the last decade, including a variety of software packages for the analysis of data sets.
Abstract: From the reviews of the First Edition. "An interesting, useful, and well-written book on logistic regression models... Hosmer and Lemeshow have used very little mathematics, have presented difficult concepts heuristically and through illustrative examples, and have included references."- Choice "Well written, clearly organized, and comprehensive... the authors carefully walk the reader through the estimation of interpretation of coefficients from a wide variety of logistic regression models . . . their careful explication of the quantitative re-expression of coefficients from these various models is excellent." - Contemporary Sociology "An extremely well-written book that will certainly prove an invaluable acquisition to the practicing statistician who finds other literature on analysis of discrete data hard to follow or heavily theoretical."-The Statistician In this revised and updated edition of their popular book, David Hosmer and Stanley Lemeshow continue to provide an amazingly accessible introduction to the logistic regression model while incorporating advances of the last decade, including a variety of software packages for the analysis of data sets. Hosmer and Lemeshow extend the discussion from biostatistics and epidemiology to cutting-edge applications in data mining and machine learning, guiding readers step-by-step through the use of modeling techniques for dichotomous data in diverse fields. Ample new topics and expanded discussions of existing material are accompanied by a wealth of real-world examples-with extensive data sets available over the Internet.
35,847 citations
TL;DR: In this paper, the role and limitations of retrospective investigations of factors possibly associated with the occurrence of a disease are discussed and their relationship to forward-type studies emphasized, and examples of situations in which misleading associations could arise through the use of inappropriate control groups are presented.
Abstract: The role and limitations of retrospective investigations of factors possibly associated with the occurrence of a disease are discussed and their relationship to forward-type studies emphasized. Examples of situations in which misleading associations could arise through the use of inappropriate control groups are presented. The possibility of misleading associations may be minimized by controlling or matching on factors which could produce such associations; the statistical analysis will then be modified. Statistical methodology is presented for analyzing retrospective study data, including chi-square measures of statistical significance of the observed association between the disease and the factor under study, and measures for interpreting the association in terms of an increased relative risk of disease. An extension of the chi-square test to the situation where data are subclassified by factors controlled in the analysis is given. A summary relative risk formula, R, is presented and discussed in connection with the problem of weighting the individual subcategory relative risks according to their importance or their precision. Alternative relative-risk formulas, R I , R2, Ra, and R4/ which require the calculation of subcategory-adjusted proportions ot the study factor among diseased persons and controls for the computation of relative risks, are discussed. While these latter formulas may be useful in many instances, they may be biased or inconsistent and are not, in fact, overages of the relative risks observed in the separate subcategories. Only the relative-risk formula, R, of those presented, can be viewed as such an average. The relationship of the matched-sample method to the subclassification approach is indicated. The statistical methodolo~y presented is illustrated with examples from a study of women with epidermoid and undifferentiated pulmonary ccrclnomc.e-J. Nat. Cancer Inst, 22: 719748, 1959.
14,433 citations
"Risk factors for contamination of d..." refers methods in this paper
...Stratified analysis, using the technique described by Mantel and Haenszel (30), or logistic regression (22) was used to assess the independent contribution of each studied variable to contamination....
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TL;DR: An explosive, common-source outbreak of pneumonia caused by a previously unrecognized bacterium affected primarily persons attending an American Legion convention in Philadelphia in July, 1976, killing 29 people, and epidemiologic analysis suggested that exposure may have occurred in the lobby of the headquarters hotel or in the area immediately surrounding the hotel.
Abstract: An explosive, common-source outbreak of pneumonia caused by a previously unrecognized bacterium affected primarily persons attending an American Legion convention in Philadelphia in July, 1976. Twenty-nine of 182 cases were fatal. Spread of the bacterium appeared to be air borne. The source of the bacterium was not found, but epidemiologic analysis suggested that exposure may have occurred in the lobby of the headquarters hotel or in the area immediately surrounding the hotel. Person-to-person spread seemed not to have occurred. Many hotel employees appeared to be immune, suggesting that the agent may have been present in the vicinity, perhaps intermittently, for two or more years.
1,468 citations
TL;DR: Initial studies with seeded material indicate that amoebal enrichment could be utilised for the isolation of legionellae from clinical specimens and natural habitats, and it is suggested that a vacuole, orAmoeba, full of Legionellae, rather than free legionelae, could be the infective particle for man.
Abstract: Legionella pneumophila, the causative organism of Legionnaires' disease, is pathogenic for free living, ubiquitous, freshwater, and soil amoebae of the genera Acanthamoeba and Naegleria. Some species support the growth of strains from serogroups 1 to 6, others only strains from certain serogroups. Initial studies with seeded material indicate that amoebal enrichment could be utilised for the isolation of legionellae from clinical specimens and natural habitats. It is suggested that a vacuole, or amoeba, full of legionellae, rather than free legionellae, could be the infective particle for man.
959 citations
"Risk factors for contamination of d..." refers background in this paper
...pneumophila was a pathogen for some amoebae (35)....
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TL;DR: The data suggest that Legionella pneumophila is part of the natural aquatic environment and that the bacterium is capable of surviving extreme ranges of environmental conditions, and demonstrate the effectiveness of the direct fluorescent-antibody technique for detecting L. pneumophILA in natural aquatic systems.
Abstract: Bacteria were concentrated 500-fold from 20-liter water samples collected from 67 different lakes and rivers in the United States. The data suggest that Legionella pneumophila is part of the natural aquatic environment and that the bacterium is capable of surviving extreme ranges of environmental conditions. The data further demonstrate the effectiveness of the direct fluorescent-antibody technique for detecting L. pneumophila in natural aquatic systems. Smears of the concentrated samples were screened microscopically for serogroups of L. pneumophila by the direct fluorescent-antibody technique. Virtually all of the 793 samples were found to be positive by this method. The 318 samples containing the largest numbers of positive bacteria which were morphologically consistent with L. pneumophila were injected into guinea pigs for attempted isolations. Isolates were obtained from habitats with a wide range of physical, chemical, and biological parameters. Samples collected monthly from a thermally altered lake and injected into guinea pigs demonstrated a seasonality of infection, with the highest frequency of infection occurring during the summer months.
558 citations
"Risk factors for contamination of d..." refers background in this paper
...These studies suggest that the distribution of legionellae is worldwide and that their concentration is directly related to water temperature (14, 19)....
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...Legionellae of all types have been isolated from natural environments in different areas of the world (12, 14, 26, 31, 32, 34)....
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