Critics Question Benefits of Broader E. coli Screening

Every week, dozens of kilograms of raw beef from meat-processing plants across the United States are rushed to one of three federal laboratories to be picked apart, pulverized, incubated and analysed. Working for the US Department of Agriculture (USDA), technicians in these labs are searching for Escherichia coli O157:H7, a toxic variety of the bacterium that has been monitored in US beef since 1994. But beginning on 4 June, the search will expand to include six more E. colisubtypes or ‘serogroups’.

US agriculture secretary Tom Vilsack announced the change last September, saying it would “stop problems before they start”. The USDA portrays the measure as a way to reduce risk, but it has not quantified the number of people that would be spared illness by the change. With the new screening protocol now imminent, meat producers are questioning the rationale behind the move and at least one outspoken expert agrees.

“I think it’s a fundamentally flawed policy, and it’s not based on the best science,” says Michael Doyle, a microbiologist and director of the Center for Food Safety at the University of Georgia in Griffin. He says that the USDA risks wasting limited resources chasing bacteria whose effects on human health are still unclear.

Most types of E. coli are harmless or even beneficial, such as those that colonize the healthy human gut. But some, such as O157:H7, can produce Shiga toxin, which can be harmful. The USDA began screening raw beef for this microbe after it was linked to the deaths of four children who ate contaminated hamburgers in 1993. Readily identifiable through rapid screening, O157:H7 can sometimes trigger haemolytic uraemic syndrome, which can cause life-threatening kidney damage.

Over the past decade, improved diagnostic tests have linked a growing number of food-borne illnesses to other Shiga-toxin-producing E. coli (STEC) serogroups, including the latest additions to the USDA’s testing regimen, dubbed the Big Six. Last year, an STEC subtype traced to contaminated fenugreek sprouts made thousands of people across Europe ill, and killed at least 53.

The Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, estimates that 173,000 STEC infections occur annually across the United States, with O157:H7 responsible for roughly 36% and the Big Six accounting for most of the remainder. By targeting these, the USDA is bringing food regulation in line with public-health data, says Robert Tauxe, deputy director of the division of food-borne, waterborne and environmental diseases at the CDC. “We think this is an important step forward in preventing human disease,” he says.

Industry representatives counter that the expanded testing will be redundant, because existing O157:H7 testing is an indicator of overall cleanliness and food safety. “We have done extensive research over the past several years that shows that the preventative controls in our facilities today work equally well for the non-O157:H7 as they do for O157,” says James Hodges, executive vice-president of the American Meat Institute (AMI), a trade association in Washington DC.

The AMI estimates that the new tests will cost the industry between US$172 million and $324 million a year, because it contends the extra sample analysis will force processors to hold onto meat longer before distributing it. More tests will also mean more false positives that require investigation, says Doyle, delaying release of the meat and lowering its market value.

The USDA acknowledges that most infections linked to the Big Six do not stem from contaminated beef but from other sources, such as vegetables. The tests will not eliminate risk of E. coli infection, says David Goldman, assistant administrator for the Office of Public Health Science at the USDA’s Food Safety and Inspection Service. Nonetheless, he says, “we expect that this is a truly preventative measure”.

The pay-offs of such a precaution are far from certain. Although the Big Six are increasingly seen as sources of illness, their toxic effects are often less severe than those of O157:H7. The serogroups are also divided into strains, not all of which produce toxins. Shiga toxins themselves occur in types that vary in toxicity by up to a factor of 1,000. Scientists are still trying to determine which strains are likely to produce the most harmful Shiga toxins, and to identify auxiliary molecules that predict a given STEC’s virulence in humans.

“We’re learning more and more, but it’s very complex,” says Phillip Tarr, a microbiologist at Washington University in St Louis, Missouri. Tauxe concedes that more research is needed to better understand STEC pathology. “This is an area that we expect to evolve,” he says. But if the meat-packing industry challenges the rule in court, as it has done for some previous USDA measures, the science of E. coli toxicity could soon find itself again under the microscope — this time, a legal one.

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Pathogen Detection Using Smartphones

Our latest newsletter describes a novel strategy for turning smartphones into portable, low-cost devices that can quickly detect a variety of pathogens. To read this article, please sign up to receive our FREE newsletter by clicking on the following link: http://rapidmicromethods.com/newsletter/. We will then email the Newsletter directly to your inbox!   

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Homeland Security To Test Biological Sensors In MBTA Tunnels

The MBTA and Department of Homeland Security are teaming up to make sure commuters are protected from biological terrorist attacks. They are testing sensors that will be able to detect hazardous materials, in the hopes of preventing future attacks.To test the sensors, the MBTA and DHS will release aerosol spray -- not harmful to the public -- into the subway system. 

Federal officials say they test the subway sensors by releasing dead bacteria called B. subtilis. They say it is used in food supplements, has been rigorously tested and has no adverse health effects for low exposure in healthy people.

Newly developed biological sensors will test the spray in the air, all in the effort to improve response time if there ever was a biological terrorist attack. The sensors will also help in other emergency situations.

Cambridge and Somerville T stations have been selected for the testing. Depending on the results of the tests, the sensors could be installed nationwide.

DHS said they selected The Massachusetts T system for testing because it is the fifth largest in the U.S., and the oldest.

“This will help us as we determine future evacuation plans, or our emergency response to any type of critical incident -- whether it be a fire, smoke in a tunnel, a HazMat spill,” said Dep. Chief Lewis Best, MBTA Transit Police.

“Improving security comes at a cost of reducing personal liberty sometimes, so I’m not always keen on it,” said Anton Ziolkowski, a commuter.

“I think that it’s probably something that should be done, something that it good for our safety. But I don’t really want to know about it beforehand when they’re doing all the testing. But it’s something that should be on the T,” said Elizabet Spatola, a commuter.

Authorities say ridership will not be greatly affected because they will be testing during the off hours in the summer.

The tests will be held during the off hours this summer, likely overnight. As part of the legal process, a hearing will be held May 16, from 5:30-7:30pm at the Cambridge YMCA in Central Square. The public will be able to voice concerns and comments.

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McMaster Researchers Develop Rapid Test Strips for Bacterial Contamination in Swimming Water

Urban beach closures due to coliform outbreaks have become disturbing signs of summer, yet water-testing technology has never been fast enough to keep up with changing conditions, nor accessible enough to check all waters.

Sentinel Bioactive Paper Network funded researchers at McMaster University have developed a rapid testing method using a simple paper strip that can detect E coli in recreational water within minutes. The new tool can close the gap between outbreak and detection, improving public safety globally.

The scientists have created and validated the viability of the test strip, which can detect potentially harmful concentrations of E coli in water quickly and simply, with much greater accuracy than existing portable technology.

The work is described in a paper published online in the journal Analytical and Bioanalytical Chemistry.

"Coliforms are always a big problem," says the paper's lead author John Brennan, a McMaster chemistry professor who holds the Canada Research Chair in Bioanalytical Chemistry. "The methods used to detect outbreaks are slow, and tend not to be portable, as they often need a lab-based amplification step prior to testing, causing a time lag between an outbreak and a beach closure."

The Natural Sciences and Engineering Research Council of Canada (NSERC) funds Sentinel Bioactive Paper, a strategic research network that spans Canada and is based at McMaster University. Several dozen researchers are involved in its initiatives to detect, repel and deactivate air, water, or food-borne pathogens to improve human health and safety.

"This is one of Sentinel's most promising technology platforms and I anticipate significant field studies in the next year," said Dr Robert Pelton, Sentinel's Scientific director and director of McMaster University Centre for Pulp and Paper Research.

Bioactive paper is both old and new, Dr Brennan explains. Since the late 1950s, physicians have been using bioactive paper to test for glucose in urine In the last several years, the area has expanded quickly and research has become very competitive as scientists work on new applications.

"It's always a race," he says.

The new strips are coated with chemicals that react to the bacteria, and are printed using inkjet technology similar to that found in standard desktop printers. Within 30 minutes of sampling, the paper changes colour to indicate the presence of E coli, with colours coded to represent different forms and concentrations of the bacteria.

In the future, the test should make it possible for consumers to check their water affordably and easily, without additional equipment, scientific knowledge or long waits.

"One of the problems right now is that there is no simple, fast and cheap way to test recreational water, and certainly nothing out there in the realm of rapid tests for drinking water," says Dr Brennan.

Field testing of the prototype strips is planned or under way in Canada and across the globe, in regions where untreated water poses particular health hazards. The results of these studies will help to refine the test strips and may lead to strips that are sensitive enough to tell whether water is safe enough to drink, says Dr Brennan.

The next stage of pre-commercial development of the test strips is already funded by NSERC through a Phase I Idea to Innovation grant. Commercialization of a final product could take as little as two to three years.

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