New Technique Developed For Quick Detection Of Salmonella

In the hours following an outbreak of salmonella, there are many questions. And answers can be hard to find. Where did the problem start? Can it be contained? Is the sickness likely to spread?

Iowa State University researchers have developed a technique for testing for the presence of salmonella that may give investigators better, faster answers.

The process, developed by Byron Brehm-Stecher, assistant professor in food science and human nutrition, and his graduate student Bledar Bisha, begins with testing the food, in most cases produce, with a strip of adhesive tape.

The tape is applied to the produce, then carefully removed, taking a sample of whatever is on the skin of the produce. That sample is then put on a slide and soaked in a special warm, soapy mixture that contains a genetic marker that binds with salmonella and gives off a fluorescent glow when viewed under an ultraviolet light. Use of this genetic marker approach is called Fluorescent In-Situ Hybridization, or FISH.

The approach can tell investigators if the produce is contaminated with salmonella in about two hours.

"This method is rapid, it's easy, and it's cheap," said Brehm-Stecher.

Current methods of detecting salmonella take one to seven days.

Brehm-Stecher and Bisha call the process "tape-FISH" and note that it could be an important technique for salmonella investigators.

"I think this will be good tool in outbreak investigation and routine surveillance especially since all you need is tape, a heat block, a small centrifuge and a fluorescence microscope," said Brehm-Stecher. "It has the potential to be very portable."

Brehm-Stecher's and Bisha's findings will be published in the journal Applied and Environmental Microbiology, published by the American Society of Microbiology.

Once at a location where an outbreak of salmonella has occurred, investigators can test the produce for contamination. Outbreaks can be due to other factors such as food preparation.

Once investigators find the origin of the salmonella, they can take steps to contain it, said Brehm-Stecher.

Salmonella can be found on produce such as tomatoes, cilantro, peppers, spinach and others. The produce can be contaminated while it is in the fields or during processing. Washing the produce thoroughly can help, but cannot ensure the produce will be safe.

The tape-FISH technique can also be used to test produce that is not suspected of being contaminated, but the volume of produce that would need to be tested may make this impractical. However, the technique could be very valuable as a basic research tool. Researchers could investigate how salmonella and other types of organisms interact on produce surfaces, said Brehm-Stecher.

This is the first application of tape-FISH to salmonella, but the idea came to the ISU researcher while reading about art restoration.

In 2008, Brehm-Stecher read about an Italian group that was using a similar approach to look for bacteria on ancient catacombs. Those researchers were hoping to identify and remove bacteria that were slowly eating away at the relics.

After some classroom discussion with his students, Brehm-Stecher decided that using the FISH on produce could be useful and began researching the idea with Bisha. Together, they were able to apply the method to produce and made several improvements in speed and sensitivity over the existing tape-FISH approach. Brehm-Stecher hopes that his tape-FISH approach can help speed investigations of produce contamination, such as last summer's outbreak of Salmonella Saintpaul, which was eventually traced to imported jalapeno and Serrano peppers.

Don’t Go Changing: New Chemical Keeps Stem Cells Young

Scientists at the Universities of Bath and Leeds have discovered a chemical that stops stem cells from turning into other cell types, allowing researchers to use these cells to develop new medical treatments more easily.

Stem cells have the ability to develop into many other cell types in the body, and scientists believe they have huge potential to treat diseases or injuries that don’t currently have a cure.

Professor Melanie Welham’s team at the University of Bath’s Department of Pharmacy & Pharmacology, collaborating with Professor Adam Nelson at the University of Leeds, have discovered a chemical that can be added to embryonic stem cells grown in the lab, allowing them to multiply without changing into other cell types.

This breakthrough will help scientists produce large stocks of cells that are needed for developing new medical therapies.

Professor Welham, who is co-director of the University of Bath’s Centre for Regenerative Medicine, explained: “Stem cells have great potential for treating spinal injuries and diseases like type I diabetes because they can change into a range of specialised cell types including nerve or pancreatic cells, which could be used to repair damaged tissues.

“Unfortunately, when you grow stem cells in the lab, they can spontaneously develop into specialised cells, making it difficult to grow large enough stocks to use for medical research.

“We’ve identified a chemical that will put this process on hold for several weeks so that we can grow large numbers of them in their unspecialised state. This is reversible, so when you take it away from the cells, they still have the ability to change into specialised cells.”

Professor Adam Nelson’s team, at the Astbury Centre for Structural Molecular Biology, made more than 50 chemical compounds that were tested for activity in the stem cells.The researchers found that the chemicals worked by blocking an enzyme, called GSK3, that can control when the stem cell switches to a more specialised cell type.

Professor Nelson, who is Director of the Astbury Centre at the University of Leeds, said: “This research is a great example of how small molecules can be used as tools to understand biological mechanisms.”

The research, supported by funding from the Biotechnology & Biological Sciences Research Council.

Gene Mutations Increase Risk For Aggressive Prostate Cancer

Men who develop prostate cancer face an increased risk of having an aggressive tumor if they carry a so-called breast cancer gene mutation, scientists from the Albert Einstein College of Medicine of Yeshiva University report in the January 29 issue of Clinical Cancer Research. The findings could help to guide prostate-cancer patients and their physicians in choosing treatment options.

The study, involving 979 men with prostate cancer and 1251 men without the disease, looked at whether participants carried mutations for either of two genes, BRCA1 and BRCA2. Women carrying mutations in either gene face an increased risk of developing breast cancer, ovarian cancer, or both.

All the people enrolled in the Einstein study were of Ashkenazi Jewish descent. The study focused on them because they are five times likelier than people in the general population to carry a mutation of any kind in the BRCA1 or BRCA2 genes. The researchers looked for the presence of three particular mutations–two in BRCA1 and one in BRCA2. Scientists believe that genetic discoveries among the Ashkenazi can benefit society as a whole in terms of preventing and treating major diseases.

Having any of the three mutations did not increase a man's risk of developing prostate cancer, the study found. But for those men who did develop prostate cancer, two of the mutations–BRCA1-185delAG and the mutated BRCA2 gene–increased the risk that tumors would be aggressive or high-grade, as defined by a Gleason score of 7 or above. The Gleason score, based on the microscopic appearance of prostate tissue removed during a biopsy or surgery, assesses the aggressiveness of a prostate tumor on a scale from 2 (least aggressive) to 10 (most aggressive).

Specifically, prostate cancer patients with high-grade, aggressive tumors (Gleason scores of 7 or above) were 3.2 times more likely to carry the BRCA2 gene mutation than were men in the control group. Carriers of the BRCA1-185delAG mutation were also at increased risk of having an aggressive prostate cancer.

Previous investigations into a possible link between prostate-cancer risk and the BRCA1 and BRCA2 genes have yielded conflicting results–perhaps because they involved small numbers of subjects and lacked well-matched control groups. "Our large study shows conclusively that prostate cancer patients with either the BRCA2 gene mutation or the BRCA1-185delAG mutation are more susceptible to aggressive cancers than people without that mutation," says Robert Burk, M.D., professor of pediatrics (genetics) at Einstein and senior author of the study.

Routine genetic testing for BRCA mutations–done by analyzing blood samples or cells swabbed from the inside of one's cheeks–wouldn't be justified for most men, says Dr. Burk: the prevalence of the mutations in the general population is very low; and men with high Gleason scores already know that their prostate cancer is aggressive. But, notes Dr. Burk, "our findings might have practical implications for some men diagnosed with early-stage (low Gleason score) prostate cancers–particularly Ashkenazi Jewish men, who are much more likely to have these mutations."

"One of the biggest problems with early-stage prostate cancer is being able to distinguish between tumors with the potential to become aggressive and those that may persist for many years without enlarging or spreading," notes Dr. Burk. For that reason, he says, Ashkenazi men diagnosed with early-stage prostate cancer might want to consider getting tested for the BRCA2 and BRCA1-185delAG mutations.

Knowing they have the mutation—and that their tumor may become aggressive—may influence treatment options that patients pursue. For example, a prostate cancer patient who has the BRCA2 mutation might vote against 'watchful waiting'—in which the growth of the cancer is monitored and treatment is held in abeyance—and instead opt for surgery or radiation treatments with or without hormone blockade therapy.

For early-stage prostate cancer patients in the general population, knowing they carry the BRCA1 or BRCA2 mutation would also be useful, says Dr. Burk. But these mutations are so rare in the general population—a prevalence of far less than one percent—that testing is unlikely to reveal their presence.

Other Einstein researchers involved in the study were Dr. Ilir Agalliu and Suzanne Leanza. The authors have no potential conflicts of interest relevant to this article.