Effect of chlorine, biodegradable dissolved organic carbon and suspended bacteria on biofilm development in drinking water systems

Codony, Francesc; Morató, Jordi; Ribas, F.; Mas, Jordi

doi:10.1002/1521-4028(200210)42:5<311::aid-jobm311>3.0.co;2-6

Cited by 21 publications

(13 citation statements)

References 26 publications

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“…In Figure 1a-c, the curves representing the numbers of cells in the biofilm (total cells, total L. pneumophila and HPC, respectively) follow the traditional shape for biofilm accumulation (Rogers et al 1994a,b;Codony et al 2002). Most of the total cells and total L. pneumophila (calculated using the L. pneumophila specific PNA probe) attached during the first few days and then fluctuated within a narrow range (p 4 0.05).…”

Section: Pneumophila In Heterotrophic Biofilmssupporting

confidence: 66%

“…This result is supported by two studies conducted by Codony et al (2002Codony et al ( , 2005, who showed that the total number of cells were similar in the control and chlorinated conditions, but treated cells were less cultivable. In the present work, HPC numbers in the control were 2-log lower than in biofilms formed in chlorinated water, although the difference between the two concentrations used was not significant (p 4 0.05).…”

Section: Pneumophila In Heterotrophic Biofilmsmentioning

confidence: 72%

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Incorporation of natural uncultivableLegionella pneumophilainto potable water biofilms provides a protective niche against chlorination stress

et al. 2009

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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.

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Section: Pneumophila In Heterotrophic Biofilmssupporting

confidence: 66%

Section: Pneumophila In Heterotrophic Biofilmsmentioning

confidence: 72%

Incorporation of natural uncultivableLegionella pneumophilainto potable water biofilms provides a protective niche against chlorination stress

et al. 2009

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“…In fact, the HPC numbers for the chlorinated biofilms were almost 3 log lower than that of the control. These results are supported by two studies conducted by Codony et al (7,8), where it was shown that under chlorinated conditions, the total number of cells was similar to that seen in the control study but that the cells were less culturable.…”

supporting

confidence: 70%

Effect of Chlorine on Incorporation of Helicobacter pylori into Drinking Water Biofilms

Gião

Azevedo

Wilks

et al. 2010

Appl Environ Microbiol

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The use of a specific peptide nucleic acid (PNA) probe demonstrated that Helicobacter pylori persisted inside biofilms exposed to low concentrations of chlorine (0.2 and 1.2 mg liter ؊1 ) for at least 26 days, although no culturable cells were recovered. Coupled with data obtained using viability stains in pure culture, this result suggests that H. pylori can survive chlorination but remain undetectable by culture methods, which can be effectively replaced by PNA hybridization.Helicobacter pylori is a Gram-negative microorganism that colonizes the human stomach and can cause gastric ulcers that can degenerate into gastric carcinoma (5). The route of transmission for this pathogen is not well known, and even though culturable H. pylori has never been isolated from drinking water distribution systems (DWDS), molecular techniques such as PCR have detected the presence of H. pylori DNA in potable water (6,15,17), indicating that this environment could act as a reservoir for this bacterium.Chlorine is the most commonly used disinfectant worldwide to ensure the safe distribution of water to the consumer (19). Although studies conducted by Johnson et al. (14) and Baker et al. (4) have shown that H. pylori is inactivated by chlorine, their conclusions were based on the lack of recovery using standard culture plating methods which fail to consider cells that have entered a viable but nonculturable (VBNC) state. Recently, Moreno et al. (16) applied molecular techniques to demonstrate that H. pylori can survive in low concentrations of chlorine in a VBNC state. However, all these studies were performed with pure cultures using suspended cells, and until now, there have been no studies reporting on the effect of chlorination on H. pylori when associated with heterotrophic biofilms where, as is well known, microorganisms become more resistant to the biocide effect of chlorine (10).In a recent study, we demonstrated that H. pylori can be incorporated into drinking water biofilms and remain viable in the lower layers of these structures (11). It is therefore important to understand the ability of this pathogen to be incorporated and survive in heterotrophic biofilms formed in chlorinated waters. If this pathogen can remain viable under these conditions, it might therefore represent a risk to public health when released into the bulk fluid.The aim of this work was to study the effect of low concentrations of chlorine on H. pylori cells both when associated with heterotrophic biofilms and when suspended in pure culture, to assess whether the biofilm can provide protection against disinfection.Incorporation of H. pylori into heterotrophic biofilms. The formation of biofilms was carried out using a two-stage chemostat model system as described elsewhere (12). The second stage consisted of three biofilm-growing vessels working in parallel. No chlorine was added to the first vessel, which served as a control, while to the other two vessels chlorine was continuously fed at a flow rate to maintain the concentrations of free chlori...

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“…As observed for planktonic samples, no cultivable H. pylori was recovered on HP on May 9, 2018 by guest http://aem.asm.org/ medium for any of the biofilm samples. The biofilm development followed kinetics described by other authors; adhesion of most cells took place on the first day, but no statistically significant change occurred after this (P Ͼ 0.05) (13,32). It should be noted that this pseudo-steady state is actually the result of a dynamic equilibrium typical of biofilms, where parts of biofilms detaching from coupons are balanced by the adherence of new cells (35,39).…”

Section: Resultsmentioning

confidence: 99%

Persistence of Helicobacter pylori in Heterotrophic Drinking-Water Biofilms

Gião

Azevedo

Wilks

et al. 2008

Appl Environ Microbiol

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Although the route of transmission of Helicobacter pylori remains unknown, drinking water has been considered a possible transmission vector. It has been shown previously that, in water, biofilms are a protective niche for several pathogens, protecting them from stressful conditions, such as low carbon concentration, shear stress, and less-than-optimal temperatures. In this work, the influence of these three parameters on the persistence and cultivability of H. pylori in drinking-water biofilms was studied. Autochthonous biofilm consortia were formed in a two-stage chemostat system and then inoculated with the pathogen. Total numbers of H. pylori cells were determined by microscopy using a specific H. pylori 16S rRNA peptide nucleic acid probe, whereas cultivable cells were assessed by standard plating onto selective H. pylori medium. Cultivable H. pylori could not be detected at any time point, but the ability of H. pylori cells to incorporate, undergo morphological transformations, persist, and even agglomerate in biofilms for at least 31 days without a noticeable decrease in the total cell number (on average, the concentration was between 1.54 ؋ 10 6 and 2.25 ؋ 10 6 cells cm ؊2 ) or in the intracellular rRNA content may indicate that the loss of cultivability was due to entry into a viable but noncultivable state. Unlike previous results obtained for pure-culture H. pylori biofilms, shear stress did not negatively influence the numbers of H. pylori cells attached, suggesting that the autochthonous aquatic bacteria have an important role in retaining this pathogen in the sessile state, possibly by providing suitable microaerophilic environments or linking biomolecules to which the pathogen adheres. Therefore, biofilms appear to provide not only a safe haven for H. pylori but also a concentration mechanism so that subsequent sloughing releases a concentrated bolus of cells that might be infectious and that could escape routine grab sample microbiological analyses and be a cause of concern for public health.Helicobacter pylori is one of the most prevalent pathogens in humans, especially in developing countries, where the incidence can be up to 90% of the population (16). Even though most individuals that are infected by this pathogen are asymptomatic, it is now well established that H. pylori infection can lead to the development of peptic and duodenal ulcer disease and gastric mucosa-associated lymphoid tissue lymphoma (8).The route of transmission of this pathogen is still unknown. Person-to-person transmission seems most likely as the only place where H. pylori has been systematically isolated is the human gastrointestinal tract (3). However, some authors have suggested that water, food, and animals can also be transmission vectors (3,7,10,19,28,37,38). The greatest obstacle to proving that water is a transmission route is the fact that H. pylori has never been cultured from drinking-water distribution systems (DWDS) using standard cultivation techniques (3, 18). Whether this is due to the fastidious nature o...

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Effect of chlorine, biodegradable dissolved organic carbon and suspended bacteria on biofilm development in drinking water systems

Cited by 21 publications

References 26 publications

Incorporation of natural uncultivableLegionella pneumophilainto potable water biofilms provides a protective niche against chlorination stress

Incorporation of natural uncultivableLegionella pneumophilainto potable water biofilms provides a protective niche against chlorination stress

Effect of Chlorine on Incorporation of Helicobacter pylori into Drinking Water Biofilms

Persistence of Helicobacter pylori in Heterotrophic Drinking-Water Biofilms

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