Test Water News and Information

		IMAGE: Georgia Tech civil and environmental engineering assistant professor Kostas Konstantinidis (left) and biology graduate student Chengwei Luo examine environmental and clinical E. coli cells, which cannot be differentiated with microscopy... Click here for more information.

The meaning of the standard fecal coliform test used to monitor water quality has been called into question by a new study that identified sources of Escherichia coli bacteria that might not indicate an environmental hazard.

Fecal pollution of surface waters is measured by the concentration of E. coli bacteria in the water because E. coli is believed to live only in the intestines and waste of humans and other warm-blooded animals, and quickly die outside its host. The presence of E. coli in water also serves as a marker for other potentially more harmful organisms that may accompany it. Positive E. coli tests may lead to the summertime closing of beaches and other recreational bodies of water.

In this new study, researchers report identifying and sequencing the genomes of nine strains of E. coli that have adapted to living in the environment independent of warm-blooded hosts. These strains are indistinguishable from typical E. coli based on traditional tests and yield a positive fecal coliform result though researchers say they may not represent a true environmental hazard.

"The basis for E. coli's widespread use as a fecal pollution indicator is the traditional thinking that E. coli cannot survive for extended periods outside a host or waste, but this study indicates that's not true," said Kostas Konstantinidis, an assistant professor in the Georgia Tech School of Civil and Environmental Engineering. "These results suggest the need to develop a new culture-independent, genome-based coliform test so that the non-hazardous environmental types of E. coli are not counted as fecal contamination."

		IMAGE: Georgia Tech biology graduate student Chengwei Luo (left) and civil and environmental engineering assistant professor Kostas Konstantinidis display petri dishes showing that strains of commensal E. coli and environmental E.... Click here for more information.

A paper describing the research was published April 11 in the early edition of the journal Proceedings of the National Academy of Sciences. The work was sponsored by the National Science Foundation and the National Institutes of Health.

Konstantinidis and Georgia Tech School of Biology graduate student Chengwei Luo compared the genomes of 25 different strains of E. coli and close relatives, which were sequenced by the Center for Microbial Ecology at Michigan State University, the Broad Institute in Massachusetts, or were publicly available in the National Center for Biotechnology Information database. Nine strains that were recovered primarily from environmental sources encoded all genes required for classification as E. coli.

"The orders-of-magnitude higher abundances of the group of organisms represented by these nine strains in environmental samples relative to those in human feces and the clinic indicate that they represent truly environmentally adapted organisms that are not associated primarily with mammal hosts," explained Konstantinidis, who also holds a joint appointment in the Georgia Tech School of Biology.

By comparing the full genomes of the samples, the Georgia Tech researchers identified 84 genes specific to or highly enriched in the genomes of the environmental E. coli and 120 genes specific to the strains commonly found in the gastrointestinal tract of healthy humans, which are called commensal E. coli. They also detected recent genetic exchange of core genes within the environmental E. coli and within the commensal strains, but not from commensal genomes to their environmental counterparts.

		IMAGE: By identifying strains of E. coli bacteria that might not indicate an environmental hazard, Georgia Tech civil and environmental engineering assistant professor Kostas Konstantinidis (left) and biology graduate student Chengwei... Click here for more information.

The environment-specific bacteria included genes important for resource acquisition and survival in the environment, such as the genes required to utilize energy sources and to break down dead cellular material. In contrast, the gastrointestinal E. coli included several genes involved in the transport and use of nutrients thought to be abundant in the gut.

"The genomic data suggest that the environmental E. coli are better at surviving in the external environment, but are less effective competitors in the gastrointestinal tract than commensal E. coli, which tells us that the environmental bacteria are highly unlikely to represent a risk to public health," explained Konstantinidis.

Collectively, this data also indicates that the environmental E. coli strains represent a distinct species from their commensal E. coli counterparts even though they are identified as E. coli based on the standard taxonomic methods. This work is consistent with a more stringent and ecologic definition for bacterial species than the current definition and suggests ways to start replacing traditional, culture-based approaches for defining diagnostic phenotypes of new species with genomic-based procedures.

The scientific, medical, regulatory and legal communities expect species to reasonably reflect the traits and habitat of an organism -- especially an organism like E. coli that has ramifications for diagnostic microbiology and for assessing fecal pollution of natural ecosystems. Efforts toward a more refined definition of this bacterial species are needed, according to Konstantinidis.

Contact: Abby Robinson
This e-mail address is being protected from spambots. You need JavaScript enabled to view it
404-385-3364
Georgia Institute of Technology Research News

The eighth Emerging Trends Symposium, initiated by Philips, took place in Cologne, Germany, the day before the start of the IDS on 20-21 March 2011.

It was attended by 50 key opinion leading dental professionals from across Europe, attracted by a roster of international speakers, each adding to the knowledge-base which is redefining oral hygiene intervention.

By the close of the symposium the assembled delegates were left in no doubt about closing the gap between the science and art of dentistry.
 
As a precursor to the introduction of two new Philips products at the close of the symposium, the event kicked off with a lecture about peri-implantitis and what is known and can be done to tackle this condition which can lead to the body's rejection of an implant.

According to the first speaker, Professor Hugo de Bruyn, peri-implantitis is an inflammatory process within the tissues surrounding the implant components, which in most cases is related to a bacterial infection.

It affects both soft and hard tissues around dental implants in a dramatic way because it leads to bone loss and is related to pocket formation and pus evacuation. This often irreversibly affects the appearance as well as position of the gums and the interior zone of the maxilla, and has aesthetic consequences leading to patient dissatisfaction.
 
Central to the treatment of peri-implantitis is biofilm removal, however there are important differences between the gums around teeth and implants which should affect the approach to oral hygiene for those with implants.

Surgical treatment is predominately based on implant surface decontamination and this is typically combined with pocket reduction and regenerative procedure's to close the defect.

The first option is a radical way to reduce the defect and improve accessibility for oral hygiene measures whilst the second option aims to avoid recurrence of disease and enhance the aesthetic outcome by defect closure.
 
Currently there are a very limited number of powerful clinical studies available which focus on etiology, pathogenesis and efficacy of peri-implantitis treatment.

Yet Professor de Bruyn questioned whether the ‘alarming rise in the disease' discussed in some papers is the reality of everyday clinical practice.

He also questioned whether it is related to changing treatment protocols or changed implant surfaces or designs which have been introduced.

His lecture concluded with an overview of the literature and treatment rationales and showed, by means of case reports, some clinical consequences, protocols and clinical guidelines related to disease prevention and treatment.
 
He was followed on the lecture podium by Dr Klaus Höcker who discoursed about whether oral hygiene is a success parameter during systematic therapy.

Dr Höcker explained that chronic periodontitis is primarily caused by the accumulation and mobilisation of bacteria on the surfaces of the teeth.

As we improve our detailed knowledge about these bacterial deposits and the pathways of periodontal breakdown, the improvement of the patient's individual oral hygiene becomes pivotal to the goal of improved periodontal therapy.

Information, instruction and the motivation of periodontally diseased patients plays a large part in a systematic treatment approach which is based on the control of plaque, infection and inflammation.

Once systematic therapy is successfully accomplished the long term success will be challenged by the practitioners' ability to keep to a high level of oral hygiene and a lifelong compliance.
 
This was backed up in an energetic talk about contemporary oral hygiene by Maria Perno Goldie who took as her theme the need to translate science into practice.

She started by providing an overview of the International Federation of Dental Hygienists (IFDH) which she heads up and provided a global perspective of the practice of dental hygiene. \

She then presented the ADHA Standards for Clinical Dental Hygiene Practice before evaluating the clinical treatment and maintenance challenges faced today by practitioners, with a focus on contemporary treatment concepts and patient recommendations.

She concluded that patient communication is a vital part of these challenges and addressed a number of intervention techniques for practitioners to use with patients.
 
Dr Paul Stoodley took as his theme Biofilm Management beyond Plaque Removal and started by explaining that dental plaque biofilm is a living community of many different types of bacteria and micro-organisms which attach and grow to tooth and gum surfaces.

The resilience of dental plaque biofilms is underlined by the ongoing management effort required to maintain good oral health.

Direct scrubbing using brush bristles is an established method of removing dental plaque biofilm, however there are many locations within the mouth, such as the interproximal spaces, gingival sulcus and pits and fissures in the occlusal grooves, which are difficult to access.

Biofilms can also be removed by fluid flow, if high enough shear forces are generated.

Dr Stoodley demonstrated that powered brushing using Philips Sonicare sonic toothbrushes, can remove biofilm formed from Strepococcus mutans, a common biofilm dental plaque cariogenic pathogen, from interproximal spaces and frontal tooth surfaces by the generated fluid flow alone.

In more inaccessible areas, where some biofilm remained, he demonstrated that fluid flow could act as a reservoir for fluoride, potentially having the beneficial effect of increasing contact time with the enamel surface.

Fluoride also reduces the degree of acidity at the tooth surface by reducing biofilm activity.
 
Building on the application of fluid flow for biofilm management, Dr Stoodly introduced the concept of the new Philips Sonicare AirFloss which uses a small volume of high velocity liquid to create high shears and jet impingement pressures to remove biofilm from interproximal spaces.

By using a typodont model and artificial biofilms comprised from biopolymers produced by biofilms, he showed how he had captured the removal from interproximal spaces using high speed imaging.

On impact the artificial biofilm in the interproximal space was immediately pushed back by the flow, the biofilm then stretched until the breaking point was reached and the biofilm detached.  He is currently developing a micro CT (X-ray) technique to visualise and quantify of S. mutans biofilms around the tooth surfaces and his research shows not only that the AirFloss can effectively remove biofilm, but also the mechanism of mechanical disruption.
 
Finally, Thomas Clos addressed the need to draw together more closely new toothbrush production methods with marketing requirements and beneficial performance for users.

During his presentation he gave an overview of the evolution of industrial toothbrush production and demonstrated the state of the art methods used today.

The pros and cons of each method were highlighted and the presentation concluded with an insight into development and production methods used for the creation of a new Philips Sonicare DiamondClean brush head.

The presentation concluded with analysis of the Sonicare DiamondClean's cleaning efficiency and showed how a toothbrush robot was developed with the ORMED Institute at University of Witten-Herdecke to allow an objective comparison and measurement of the cleaning efficiency of various toothbrushes.
 
At the climax of the symposium the assembled delegates were given a preview and insight into the research and clinical effectiveness of two new Philips Sonicare products which were launched the following day at the IDS.

The new Philips Sonicare AirFloss is the first interdental cleaning device which uses microburst technology to clean interproximally whilst Philips Sonicare DiamondClean power toothbrush is considered the most sophisticated, high performance Sonicare toothbrush to date.  Questioned immediately after they had tried AirFloss, 86% of the symposium delegates found it easier to use than string floss, while 64% of those surveyed would recommend AirFloss to their patients.

Biofilms are microbial communities encased in a layer of extracellular polymeric substances (EPS).The EPS matrix provides several functional purposes for the biofilm, such as protecting bacteria fromenvironmental stresses, and providing mechanical stability. Quorum sensing is a cell-cell communicationmechanism used by several bacterial taxa to coordinate gene expression and behaviour in groups, based onpopulation densities.Model: We mathematically model quorum sensing and EPS production in a growing biofilm under variousenvironmental conditions, to study how a developing biofilm impacts quorum sensing, and conversely, how abiofilm is affected by quorum sensing-regulated EPS production.

We investigate circumstances when using quorum-sensing regulated EPS production is a beneficial strategy for biofilm cells.

Results: We find that biofilms that use quorum sensing to induce increased EPS production do not obtain thehigh cell populations of low-EPS producers, but can rapidly increase their volume to parallel high-EPSproducers. Quorum sensing-induced EPS production allows a biofilm to switch behaviours, from a colonizationmode (with an optimized growth rate), to a protection mode.

Conclusions: A biofilm will benefit from using quorum sensing-induced EPS production if bacteria cells have theobjective of acquiring a thick, protective layer of EPS, or if they wish to clog their environment with biomass asa means of securing nutrient supply and outcompeting other colonies in the channel, of their own or a different species.

Author: Mallory FrederickChristina KuttlerBurkhard HenseHermann Eberl
Credits/Source: Theoretical Biology and Medical Modelling 2011, 8:8