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At least 541 records · Page 30Linked to original sources
PubMed1987

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.

Chlorine↗
PubMed1990

Microbiological aspects of aerobic thermophilic treatment of swine waste.

A thermophilic strain (D2) identified as a Bacillus sp. was isolated from an aerobic digestor of swine waste after several months of operation at 55 degrees C. Aerobic thermophilic batch treatment of swine waste inoculated with strain D2 was studied in a 4-liter fixed-bed reactor. Stabilization of the waste was achieved in less than 30 h when the original chemical oxygen demand (COD) was between 15 and 20 g/liter or in less than 48 h when the COD was around 35 g/liter. When the COD was higher than 30 g/liter, the pH of the waste reached 9.2 to 9.5 during the treatment, and periodic adjustment of the pH to 8.5 was necessary to maintain the activity of the biofilm. In this reactor, ammoniacal nitrogen was completely eliminated by desorption in less than 72 h of incubation. The different packing materials used resulted in similar rates of degradation of organic matter. The thermophilic treatment was also efficient in the 75-liter digestor, and stabilization was achieved in approximately 50 h. A bank of 22 thermophilic bacterial strains originating from different environments and adapted to the thermophilic treatment of swine waste was established. This thermophilic treatment allows, in one step, rapid stabilization of the waste, elimination of the bad smell, and complete elimination of ammonia nitrogen by stripping.

Aerobiosis↗
PubMed1994

Comparison of the microbiological quality of water coolers and that of municipal water systems.

The microbiological quality of tap water and that of water from 50 water coolers located in residences and workplaces were comparatively studied. In addition, difference factors that might influence the bacteriological contamination of water dispensers were examined. Aeorbic and facultative anaerobic heterotrophic bacteria, total coliforms, and two indicators for fecal contamination (fecal coliforms and fecal streptococci) as well as three types of pathogenic bacteria (Staphylococcus aureus, Pseudomonas aeruginosa, and Aeromonas spp.) were enumerated. It was found that 36 and 28% of the water dispenser samples from the residences and the workplaces, respectively, were contaminated by a least one coliform or indicator bacterium and/or at least one pathogenic bacterium. The respective proportions of tap water samples contaminated in a similar fashion were 18 and 22%, much less than those observed for water coolers (Chi2(1) = 3.71, P = 0.05). We were unable to discern the dominant factors responsible for the contamination of water coolers, but cleaning the water dispenser every 2 months seemed to limit the extent of contamination.

Drinking↗
PubMed1994

Influence of temperature and plumbing material selection on biofilm formation and growth of Legionella pneumophila in a model potable water system containing complex microbial flora.

Survival and growth of Legionella pneumophila in both biofilm and planktonic phases were determined with a two-stage model system. The model used filter-sterilized tap water as the sole source of nutrient to culture a naturally occurring mixed population of microorganisms including virulent L. pneumophila. At 20 degrees C, L. pneumophila accounted for a low proportion of biofilm flora on polybutylene and chlorinated polyvinyl chloride, but was absent from copper surfaces. The pathogen was most abundant on biofilms on plastics at 40 degrees C, where it accounted for up to 50% of the total biofilm flora. Copper surfaces were inhibitory to total biofouling and included only low numbers of L. pneumophila organisms. The pathogen was able to survive in biofilms on the surface of the plastic materials at 50 degrees C, but was absent from the copper surfaces at the same temperature. L. pneumophila could not be detected in the model system at 60 degrees C. In the presence of copper surfaces, biofilms forming on adjacent control glass surfaces were found to incorporate copper ions which subsequently inhibited colonization of their surfaces. This work suggests that the use of copper tubing in water systems may help to limit the colonization of water systems by L. pneumophila.

Bacterial Adhesion↗
PubMed2004

Mycobacteria in water and loose deposits of drinking water distribution systems in Finland.

Drinking water distribution systems were analyzed for viable counts of mycobacteria by sampling water from waterworks and in different parts of the systems. In addition, loose deposits collected during mechanical cleaning of the main pipelines were similarly analyzed. The study covered 16 systems at eight localities in Finland. In an experimental study, mycobacterial colonization of biofilms on polyvinyl chloride tubes in a system was studied. The isolation frequency of mycobacteria increased from 35% at the waterworks to 80% in the system, and the number of mycobacteria in the positive samples increased from 15 to 140 CFU/liter, respectively. Mycobacteria were isolated from all 11 deposits with an accumulation time of tens of years and from all 4 deposits which had accumulated during a 1-year follow-up time. The numbers of mycobacteria were high in both old and young deposits (medians, 1.8 x 10(5) and 3.9 x 10(5) CFU/g [dry weight], respectively). Both water and deposit samples yielded the highest numbers of mycobacteria in the systems using surface water and applying ozonation as an intermediate treatment or posttreatment. The number and growth of mycobacteria in system waters correlated strongly with the concentration of assimilable organic carbon in the water leaving the waterworks. The densities of mycobacteria in the developing biofilms were highest at the distal sites of the systems. Over 90% of the mycobacteria isolated from water and deposits belonged to Mycobacterium lentiflavum, M. tusciae, M. gordonae, and a previously unclassified group of mycobacteria. Our results indicate that drinking water systems may be a source for recently discovered new mycobacterial species.

Biofilms↗
PubMed1967

Floc sizing techniques.

In the study of mass transfer of substrate through floc particles, it is essential to have an estimate of floc size. This study presents floc size measurements made on pure culture bacterial floc and shows their applicability to mass transfer studies. A critical review of the biological literature on methods to size biological floc and determine wet floc density is also presented.

Bacteriological Techniques↗
PubMed1967

Viral depuration of the Northern quahaug.

A study was conducted to evaluate critically the feasibility of using the self-cleansing mechanism as a practical means to obtain virus-free shellfish. Two systems supplied with fresh running seawater, three strains of human enterovirus and the Northern quahaug, were used as working models. Preliminary experiments in the experimental system under arbitrarily selected conditions showed that depuration of poliovirus-polluted quahaugs could be achieved by the method used for the Eastern oyster. The factors affecting viral depuration studied so far included: (i) initial concentration of shellfish pollution; (ii) temperature of seawater; and (iii) salinity of seawater. It was shown that purification of the lightly polluted shellfish was achieved sooner than of the heavily polluted ones. The efficiency of viral depuration was roughly a function of the water temperature within the range tested (5 to 20 C). Reduction of salinity to 50 to 60% of the original level stopped this process completely, but 25% reduction in salinity did not affect significantly the rate of depuration. Preliminary study in the pilot system showed that viral depuration in the large tank appeared to be equally as efficient as that in the small experimental tanks under the particular conditions.

Enterovirus↗
PubMed1975

Screening test for assessment of ultimate biodegradability: linear alkylbenzene sulfonates.

A relatively simple shake-flask system for determining CO2 evolution was developed to assess the ultimate biodegradability by soil and sewage micro-organisms of chemicals which enter the environment. Linear alkylbenzene sulfonates (LAS) were used as model compounds to evaluate the method and were found to undergo substantial biodegradation in this dilute system. At the 30 mg/liter test concentration, higher-molecular-weight LAS compounds were biodegraded at a slower rate and to a lesser extent than lower-molecular-weight LAS, an effect which was eliminated or greatly reduced upon incremental addition of the LAS to the test medium during the first week of incubation. LA35S was used to demonstrate rapid LAS desulfonation, and 14CO2 evolution studies with (14C) benzene ring-labeled LAS indicated concomitant biodegradation of the entire LAS molecule as well as the LAS aromatic component. The test can be employed to examine numerous compounds at the same time and is readily adapted to studies of the effect of variation in temperature and oxygen concentration on biodegradation.

Bacteria↗
PubMed1996

Field inversion gel electrophoretic analysis of Legionella pneumophila strains associated with nosocomial legionellosis in children.

Two nosocomial cases of Legionnaires' disease occurred in children. Legionella pneumophila serogroup 1 was isolated from both patients and 30 of 39 plumbing system sites in the hospital. The patient and hospital environmental isolates yielded identical field inversion gel electrophoretic patterns which differed from patterns observed with epidemiologically unrelated strains.

Child↗
PubMed1997

Outbreak of Shigella sonnei in a clinical microbiology laboratory.

Laboratory technologists (22%) developed infections with Shigella sonnei. The isolates had the same antibiogram and pulse-field gel electrophoresis pattern as an unknown isolate handled by a laboratory student. Covering faucet handles with paper towels during hand washing in the laboratory was protective. No further cases occurred after the laboratory was cleaned with a phenolic agent and a handle-free faucet was installed.

DNA, Bacterial↗
PubMed2001

Barriers to safe hot tap water: results from a national study of New Zealand plumbers.

INTRODUCTION: Many countries still have unacceptably high hospitalizations and deaths from scalds from hot tap water. Prevention strategies implemented in some countries may not work in others. Legislation aimed at changing environments that are conducive to hot tap water scalds may not be effective in many situations for a number of reasons, including lack of acceptability and practicality. METHOD: A qualitative study of a purposefully selected group of craftsman plumbers across New Zealand was conducted using a structured format with open ended questions. The questionnaire was administered by telephone. Information was sought on the opinions, knowledge, and practice of these plumbers regarding hot tap water safety in homes. RESULTS: Several barriers to hot tap water safety in homes were identified by the plumbers. These included common characteristics of homes with unsafe hot tap water, such as hot water systems heated by solid fuel, and public ignorance of hot tap water safety. Other factors that emerged from the analysis included a lack of knowledge by plumbers of the hazards of hot tap water, as well as a lack of importance given to hot tap water safety in their plumbing practice. Shower performance and the threat to health posed by legionella were prioritized over the prevention of hot tap water scalds. CONCLUSION: The findings of this study allow an understanding of the practical barriers to safe hot tap water and the context in which interventions have been applied, often unsuccessfully. This study suggests that plumbers can represent a barrier if they lack knowledge, skills, or commitment to hot tap water safety. Conversely, they represent a potential source of advocacy and practical expertise if well informed, skilled, and committed to hot tap water safety.

Accident Prevention↗
PubMed1984

Pseudomonas in the sinks in an intensive care unit: relation to patients.

Sink drains in a medical-surgical intensive care unit (ICU) were cultured during six consecutive weeks as part of a seven month prospective study of acquisition of Pseudomonas aeruginosa by ICU patients. Isolates were typed serologically and by aminoglycoside and chlorhexidine susceptibility patterns. All 11 sinks contained multiple strains of P aeruginosa; some strains persisted for weeks while others were isolated once. Of the sink isolates 56% had high level resistance to gentamicin and tobramycin whereas none of the strains found in patients. In sink isolates chlorhexidine resistance correlated with aminoglycoside resistance and with the presence of a chlorhexidine dispenser at a sink. The sequence of recovery of phenotypically similar isolates suggested that sinks were the source of at most two acquisitions of P aeruginosa by patients during the six weeks. Our study confirms that sinks may be reservoirs for large numbers of highly resistant P aeruginosa but are rarely the source of organisms colonising patients in our ICU.

Aminoglycosides↗
PubMed1983

Distribution of lead in body fluids after ingestion of soft solder.

Blood, serum, cerebrospinal fluid, and urine obtained from a patient before and after chelation therapy showed that (1) the ratio of Pb in his cerebrospinal fluid to that in his serum varied from 0.4 to 0.9 and was independent of serum Pb concentration; (2) the fraction of Pb in his serum fell linearly with decreasing blood Pb concentration and changed from 1.6% to 0.33% as his blood Pb concentration changed from 116 micrograms/dl (5.6 mumol/l) to 31 micrograms/dl (1.5 mumol/l); and (3) his renal clearance of Pb from serum varied from 5 ml/min to 36 ml/min. This high value was obtained 11 days after chelation and is attributed to large quantities of Sn in his urine promoting the excretion of Pb. Solder was identified in his stool after discovery of radio-opaque material in his bowel. The Pb isotope ratios of the solder were different from those in his urine when he was first admitted, and showed that he had ingested solder when he had returned home on weekend passes.

Body Fluids↗