Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: UMLS:C0023241 (Legionella)
6,990 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The aim of this study was to evaluate the efficacy of copper and silver ions and of free chlorine in different combinations and concentrations (0.4 to 0.8-0.04 to 0.08 mg/l Cu(2+) Ag(+); 0.4 to 0.8-0.04 to 0.08-0.2 mg/l Cu(2+) Ag(+) Cl; 0.4 to 0.8-0.04 to 0.08-2 mg/l Cu(2+) Ag(+) Cl; 0.4 to 0.8-0.04 to 0.08-4 mg/l Cu(2+) Ag(+) Cl; 2-20 mg/l Cl), in inactivating Legionella pneumophila in drinking and distilled water after a contact time of 24-hours. Treatment with chlorine alone at 20 mg/l concentration was found to be the most effective treatment leading to complete killing of bacteria within 4 minutes in all water samples. On the other hand, at 2 mg/l concentration complete inactivation was obtained after 3 hours. The association of copper and silver ions at concentrations of 0.4-0.04 mg/l was found to be less effective and live bacteria could still be identified in all water samples after a 24 hour contact time. When testing copper and silver ions in combination, at concentrations of 0.8-0.08 mg/l and different combinations of the three disinfectants, results varied according to the various concentrations and type of water. The combination of copper and silver with 2 mg/l of chlorine was found to be more effective than 2mg/l of chlorine alone; a synergistic effect can therefore be hypothesized. The physical and chemical properties of drinking water, in particular its chlorine content, may have affected the water disinfection process when disinfecting agents were used in low concentrations. In conclusion, this study confirms the efficacy of shock hyperchlorination in the inactivation of Legionella pneumophila. However, the combination of free chlorine with metal (copper and silver) ions may represent a valid option for reducing the concentration of disinfectants to safer levels for human health and avoiding damage to water distribution systems especially in facilities such as hotels and hospitals.
...
PMID:Inactivation of Legionella pneumophila by combined systems of copper and silver ions and free chlorine. 1837 4

This paper describes the results of a five-year monitoring programme applied to the water distribution system of the University Hospital of Pisa (Italy). The purpose of the programme was to evaluate the efficacy of an integrated water safety plan in controlling Legionella spp. colonisation of the potable water system. The impact of the safety plan on the ecology of legionella in the water network was evaluated by studying the genetic variability and the chlorine susceptibility of the strains isolated prior to, and throughout, the application of continuous chlorine dioxide treatment. After 45 months of water hyperchlorination, Legionella spp. were still present but the positive supply points were reduced by 79.4%. The samples exceeding 10(3)cfu/L were reduced by 83.8% and the mean counts showed a decrease of 94.6%. The majority of the isolates belonged to Legionella pneumophila serogroup 1 (overall positivity rate: 161/423; 38%). Molecular typing was performed on 61 isolates (37.9% of the positive samples) selected on spatial and temporal criteria. This revealed the circulation and the persistence in the hospital environment of three prevalent types of L. pneumophila Wadsworth, demonstrating allelic and electrophoretic characteristic profiles and different chlorine susceptibility. Two of these, one predominant and pre-dating the sanitation regimen, and one other isolated after three years of water treatment, were chlorine tolerant. Despite the ineffectiveness of chlorine dioxide in eradicating L. pneumophila, the risk management plan adopted appeared to discourage further cases of nosocomial legionellosis.
...
PMID:Molecular epidemiology of Legionella pneumophila serogroup 1 isolates following long-term chlorine dioxide treatment in a university hospital water system. 1843 18

Legionella pneumophila is the causative agent of Legionnaires' disease. This bacterium is ubiquitous in aqueous environments and uses amoebae as an intracellular replicative niche. Real-time PCR has been developed for rapid detection of Legionella DNA in water samples. In addition to culturable bacteria, this method may also detect dead and viable but noncultivable (VBNC) legionellae. In order to understand the significance of positive PCR results in this setting, we prepared water samples containing known concentrations of L. pneumophila and analyzed them comparatively by means of conventional culture, real-time PCR, viability labeling, and immunodetection (solid-phase cytometry). We also examined the influence of chlorination on the results of the four methods. The different techniques yielded similar results for nonchlorinated water samples but not for chlorinated samples. After treatment for 24 h with 0.5 and 1 ppm chlorine, all cultures were negative, PCR and immunodetection showed about 10(6) genome units and bacteria/ml, and total-viable-count (TVC) labeling detected 10(5) and 10(2) metabolically active bacteria/ml, respectively. Thus, PCR also detected bacteria that were VBNC. The recoverability of VBNC forms was confirmed by 5 days of coculture with Acanthamoeba polyphaga. Therefore, some TVC-positive bacteria were potentially infective. These data show that L. pneumophila PCR detects not only culturable bacteria but also VBNC forms and dead bacterial DNA at low chlorine concentrations.
...
PMID:A PCR-based method for monitoring Legionella pneumophila in water samples detects viable but noncultivable legionellae that can recover their cultivability. 1851 76

The ability of Legionella pneumophila to colonise domestic water systems is a primary cause of outbreaks of Legionnaire's disease in humans. World Health Organization guidelines recommend that drinking water is chlorinated to between 0.2 and 1mg/L [Chlorine in drinking-water. Guidelines for drinking-water quality, 2nd edn. Geneva: World Health Organization; 1996], but L. pneumophila is repeatedly isolated from chlorinated water systems, indicating that this treatment is not effective at preventing colonisation. Current UK guidelines recommend a one-off treatment of 20-50mg/L of free chlorine to remove the bacteria. In this study we report on the persistence of L. pneumophila serogroup 1 in a domestic shower system despite repeated cycles of chlorination at 50mg/L for 1h exposure time, over the course of two and a half years. Persisting isolates were subjected to in-vitro phenotypic analyses and polymerase chain reaction analysis for the toxin-encoding mip gene. Random amplified polymorphic DNA typing was also performed to determine whether the isolates recovered on different occasions were the same strain. We found that seven isolates of L. pneumophila recovered over a two-and-a-half year period are the same genetically defined strain, indicating that the bacteria can persist despite repeated cycles of chlorination after each successive isolation.
...
PMID:Long-term persistence of a single Legionella pneumophila strain possessing the mip gene in a municipal shower despite repeated cycles of chlorination. 1872 53

Legionella organisms are prevalent in manmade water systems and cause legionellosis in humans. A rapid detection method for viable Legionella cells combining ethidium monoazide (EMA) and PCR/real-time PCR was assessed. EMA could specifically intercalate and cleave the genomic DNA of heat- and chlorine-treated dead Legionella cells. The EMA-PCR assay clearly showed an amplified fragment specific for Legionella DNA from viable cells, but it could not do so for DNA from dead cells. The number of EMA-treated dead Legionella cells estimated by real-time PCR exhibited a 10(4)- to 10(5)-fold decrease compared to the number of dead Legionella cells without EMA treatment. Conversely, no significant difference in the numbers of EMA-treated and untreated viable Legionella cells was detected by the real-time PCR assay. The combined assay was also confirmed to be useful for specific detection of culturable Legionella cells from water samples obtained from spas. Therefore, the combined use of EMA and PCR/real-time PCR detects viable Legionella cells rapidly and specifically and may be useful in environmental surveillance for Legionella.
...
PMID:Specific detection of viable Legionella cells by combined use of photoactivated ethidium monoazide and PCR/real-time PCR. 1897 73

Legionella pneumophila is an ubiquitous environmental microorganism that can cause Legionnaires' disease or Pontiac fever. As a waterborne pathogen, it has been found to be resistant to chlorine disinfection and survive in drinking water systems, leading to potential outbreaks of waterborne disease. In this work, the effect of different concentrations of free chlorine was studied (0.2, 0.7, and 1.2 mg l(-1)), the cultivability of cells assessed by standard culture techniques (buffered charcoal yeast extract agar plates) and viability using the SYTO 9/propidium iodide fluorochrome uptake assay (LIVE/DEAD BacLight). Results demonstrate that L. pneumophila loses cultivability after exposure for 30 min to 0.7 mg l(-1) of free chlorine and in 10 min when the concentration is increased to 1.2 mg l(-1). However, the viability of the cells was only slightly affected even after 30 min exposure to the highest concentration of chlorine; good correlation was obtained between the rapid SYTO 9/propidium iodide fluorochrome uptake assay and a longer cocultivation with Acanthamoeba polyphaga assay, confirming that these cells could still recover their cultivability. These results raise new concerns about the assessment of drinking water disinfection efficiency and indicate the necessity of further developing new validated rapid methods, such as the SYTO 9/propidium iodide uptake assay, to assess viable but noncultivable L. pneumophila cells in the environment.
...
PMID:Validation of SYTO 9/propidium iodide uptake for rapid detection of viable but noncultivable Legionella pneumophila. 1904 57

Legionella pneumophila is a waterborne pathogen that has been isolated sporadically from drinking water distribution systems (DWDS). Resistance to disinfectants is mainly attributed to the association of cells with amoebae, but biofilms are also thought to provide some degree of protection. In the present work, a two-stage chemostat was used to form heterotrophic biofilms from drinking water to study the influence of chlorine on the presence of naturally occurring L. pneumophila. The pathogen was tracked in planktonic and sessile biofilm phases using standard culture recovery techniques for cultivable cells and a peptide nucleic acid fluorescence in situ hybridisation assay for total cells. The results showed that the total number of L. pneumophila cells in biofilms was not affected by the concentrations of chlorine tested, and the presence of L. pneumophila could not be detected by culturing. To restrict the outbreaks of disease caused by this bacterium, efforts need to be concentrated on preventing L. pneumophila from re-entering an infectious state by maintaining residual disinfectant levels through the entire DWDS network so that the resuscitation of cells via contact with amoebae is prevented.
...
PMID:Incorporation of natural uncultivable Legionella pneumophila into potable water biofilms provides a protective niche against chlorination stress. 1924 Dec 30

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.
...
PMID:Viability PCR, a culture-independent method for rapid and selective quantification of viable Legionella pneumophila cells in environmental water samples. 1936 80

The aspects of hot water supply, which determine the safety of hot water delivered to the population, are considered. The authors underline the antiepidemic value of hot water temperature maintenance at the water pumping points of not below 60 degrees C as only this measure liably prevents water multiplication of Legionella pneumophila that induces legionellosis, a severe disease, as well as other high temperature-resistant microorganisms. The results of estimating the residential use of hot water, according to which the hot water script is diverse and accounts for as many as 17 different operations made by women and, in some cases, taken an average of 1.5 hours to the maximum of up to 4 hours a day, are given. There is a need for mandatory monitoring for the level of chloroform in the chlorine-decontaminated water supplied to the population.
...
PMID:[Topical aspects of hot water supply to the population]. 1951 95

The presence of Legionella spp. in potable water systems is a major concern to municipal water providers and consumers alike. Despite the inclusion of chlorine in potable supplies and frequent chlorination cycles, the bacterium is a recalcitrant human pathogen capable of causing incidents of Legionnaires' disease, Pontiac fever and community-acquired pneumonia in humans. Using two materials routinely employed for the delivery of potable water as a substratum, copper and stainless steel, the development of Legionella pneumophila biofilms and their response to chlorination was monitored over a three-day and a three-month period, respectively. Preliminary in vitro studies using broth and sterile tap water as culture media indicated that the bacterium was capable of surviving in low numbers for 28 days in the presence of chlorine. Subsequently, biofilms were grown for three days, one month and two months, respectively, on stainless steel and copper sections, which are widely used for the conveyance of potable water. Immediately after exposure to 50mg/L chlorine for 1h, the biofilms yielded no recoverable colonies, but colonies did reappear in low numbers over the following days. Despite chlorination at 50mg/L for 1h, both one- and two-month-old L. pneumophila biofilms were able to survive this treatment and to continue to grow, ultimately exceeding 1x10(6)cfu per disc. This research provides an insight into the resistance afforded to L. pneumophila against high levels of chlorine by the formation of biofilms and has implications for the delivery of potable water.
...
PMID:Resistance of Legionella pneumophila serotype 1 biofilms to chlorine-based disinfection. 1978 74


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---