Category Archives: Pathogens and Diseases

Antibiotic resistance mechanism in bacteria found

Scientists have found that nitric oxide produced by the bacteria eliminates some key effects of a wide range of antibiotics.

The latest research, done by a team at New York University, showed that in bacteria the production of nitric oxide – a small molecule made up of one nitrogen and one oxygen atom – increased their resistance to antibiotics.

This could very likely advance the science in dealing with antibiotic resistance bacteria.

Full report here by BBC News.

Antibiotic resistance clue found

US scientists have uncovered a defence mechanism in bacteria that allows them to fend off the threat of antibiotics.

It is hoped the findings could help researchers boost the effectiveness of existing treatments.

The study published in Science found that nitric oxide produced by the bacteria eliminates some key effects of a wide range of antibiotics.

One UK expert said inhibiting nitric oxide synthesis could be an important advance for tackling tricky infections.

Antibiotic resistance, for example with MRSA, is a growing problem and experts have long warned of the need to develop new treatments.

“ Here, we have a short cut, where we don’t have to invent new antibiotics ”
Dr Evgeny Nudler, study leader

The latest research, done by a team at New York University, showed that in bacteria the production of nitric oxide – a small molecule made up of one nitrogen and one oxygen atom – increased their resistance to antibiotics.

They found the enzymes responsible for producing nitric oxide were activated specifically in response to the presence of the antibiotics.

They also showed that nitric oxide alleviates damage caused by the drugs as well as helping to neutralise many of the toxic compounds within the antibiotic.

The researchers then showed that eliminating nitric oxide production in the bacteria allowed the antibiotics to work at lower, less toxic doses.

More effective

Study leader, Dr Evgeny Nudler, said developing new medicines to fight antibiotic resistance, such as that seen with MRSA is a “huge hurdle”.

“Here, we have a short cut, where we don’t have to invent new antibiotics.

“Instead we can enhance the activity of well-established ones, making them more effective at lower doses.

Dr Matthew Dryden, consultant in microbiology and communicable disease at Royal Hampshire County Hospital and general secretary of the British Society for Antimicrobial Chemotherapy, said if the enzyme which creates nitric oxide could be inhibited, it could suppress the ability of the bacteria to counteract antibiotics.

“This would be a useful therapeutic advance, especially as we are running out of new classes of antibiotics and there is less antibiotic development in general.”

Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/2/hi/health/8248020.stm

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Breast Cancer Cells Grow Under Influence of Fish Flesh

Bringing Cancer to the Dinner Table: Breast Cancer Cells Grow Under Influence of Fish Flesh
Tests of river fish indicate their flesh carries enough estrogen-mimicking chemicals to cause breast cancer cells to grow

By David Biello

Many streams, rivers and lakes already bear warning signs that the fish caught within them may contain dangerously high levels of mercury, which can cause brain damage. But, according to a new study, these fish may also be carrying enough chemicals that mimic the female hormone estrogen to cause breast cancer cells to grow. “Fish are really a sentinel, just like canaries in the coal mine 100 years ago,” says Conrad Volz, co-director of exposure assessment at the University of Pittsburgh Cancer Institute’s Center for Environmental Ecology. “We need to pay attention to chemicals that are estrogenic in nature, because they find their way back into the water we all use.”
Volz and colleagues, including biochemist Patricia Eagon, took samples from 21 catfish and six white bass donated by local anglers as part of a study presented at the American Association for Cancer Research meeting in Los Angeles this week. The fish were caught in five places: a relatively unpolluted site 36 miles upstream from Pittsburgh on the Allegheny River; an industrial site on the Monongahela River; an Allegheny site downstream from several industries that release toxic chemicals; and the confluence of the Allegheny and Monongahela rivers, where Pittsburgh dumps much of its treated sewage and sewer outflows. “This is the largest concentration of combined sewer outflows in the U.S.,” Volz notes, about the confluence, known as the Point. The researchers also bought several fish at the store as controls.

Using an organic solvent, the researchers created an extract from the skin, flesh and fat of the various fish. They then bathed a breast cancer cell line—known as MCF-7—in the extract. “We used this cell line because it has estrogen receptors in it, meaning that if estrogens are present it causes this cell line to proliferate,” Volz explains. “If you put something on it and it grows, then it must be stimulating the estrogen receptor.” In addition to responding to pure estrogen applied as a positive control, the extract from two of the white bass and five of the catfish caused the breast cancer cells to thrive.

The highest response came from fish caught in the industrial section of the Monongahela River. “The Monongahela River area is the area in Pittsburgh that was the site of most of the steel production over the last 100 years,” Volz says. “That area is still an industrial beehive.” But the broadest response came from where the sewer outflows and sewage treatment plants flow into the rivers from Pittsburgh; three of the four catfish caught here caused the breast cancer cells to proliferate. “Sewage might be more responsible for putting estrogenic chemicals in the water than the industries alone,” Volz adds. “All of the hormone replacement products that women use go down the drain, along with birth control pills, antibacterial soaps, and many of the plastics we use, like Bisphenol A, have such effects.”

It remains unclear exactly what estrogen-mimicking chemicals were actually present in the fish and what kind of cancer-causing role they might have. But their effects on the fish themselves were clear: the gender of nine of the fish could not be determined. “Increased estrogenic active substances in the water are changing males so that they are indistinguishable from females,” Volz says. “There are eggs in male gonads as well as males are secreting a yolk sac protein. Males aren’t supposed to be making egg stuff.”

And this estrogen burden is widespread. The store-bought white bass caused breast cancer cells to grow like its river-caught counterparts (as well as containing higher levels of mercury, arsenic and other contaminants) after being trucked to Pittsburgh from Lake Erie. “These fish, again, were in waters that were seeing industrial waste as well as possible combined sewer outflows,” Volz notes. “This isn’t just happening in Pittsburgh, this is happening everywhere in the industrialized world.”

Volz says he and his fellow researchers are launching a broader survey this summer that will entail sampling fish all along the Allegheny River. Efforts will be made to determine if it is industrial waste, sewage or agricultural runoff—or all three—that is responsible for the problem. In the meantime, cooking the fat out of fish may be the best defense. “If you broil fish and let the fats drip out that will take most of the contaminants out,” Volz says, though that may not be enough given other exposures to potentially tainted water. “What our study does show us is that there is exposure potential to vast populations that use water from our rivers as their drinking water supply.”

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Antibacterial Products May Do More Harm Than Good

From Scientific American

Strange but True: Antibacterial Products May Do More Harm Than Good
Antibacterial soaps and other cleaners may actually be aiding in the development of superbacteria.
By Coco Ballantyne

Tuberculosis, food poisoning, cholera, pneumonia, strep throat and meningitis: these are just a few of the unsavory diseases caused by bacteria. Hygiene—keeping both home and body clean—is one of the best ways to curb the spread of bacterial infections, but lately consumers are getting the message that washing with regular soap is insufficient. Antibacterial products have never been so popular. Body soaps, household cleaners, sponges, even mattresses and lip glosses are now packing bacteria-killing ingredients, and scientists question what place, if any, these chemicals have in the daily routines of healthy people.
Traditionally, people washed bacteria from their bodies and homes using soap and hot water, alcohol, chlorine bleach or hydrogen peroxide. These substances act nonspecifically, meaning they wipe out almost every type of microbe in sight—fungi, bacteria and some viruses—rather than singling out a particular variety.

Soap works by loosening and lifting dirt, oil and microbes from surfaces so they can be easily rinsed away with water, whereas general cleaners such as alcohol inflict sweeping damage to cells by demolishing key structures, then evaporate. “They do their job and are quickly dissipated into the environment,” explains microbiologist Stuart Levy of Tufts University School of Medicine.

Unlike these traditional cleaners, antibacterial products leave surface residues, creating conditions that may foster the development of resistant bacteria, Levy notes. For example, after spraying and wiping an antibacterial cleaner over a kitchen counter, active chemicals linger behind and continue to kill bacteria, but not necessarily all of them.

When a bacterial population is placed under a stressor—such as an antibacterial chemical—a small subpopulation armed with special defense mechanisms can develop. These lineages survive and reproduce as their weaker relatives perish. “What doesn’t kill you makes you stronger” is the governing maxim here, as antibacterial chemicals select for bacteria that endure their presence.

As bacteria develop a tolerance for these compounds there is potential for also developing a tolerance for certain antibiotics. This phenomenon, called cross-resistance, has already been demonstrated in several laboratory studies using triclosan, one of the most common chemicals found in antibacterial hand cleaners, dishwashing liquids and other wash products. “Triclosan has a specific inhibitory target in bacteria similar to some antibiotics,” says epidemiologist Allison Aiello at the University of Michigan School of Public Health.

When bacteria are exposed to triclosan for long periods of time, genetic mutations can arise. Some of these mutations endow the bacteria with resistance to isoniazid, an antibiotic used for treating tuberculosis, whereas other microbes can supercharge their efflux pumps—protein machines in the cell membrane that can spit out several types of antibiotics, Aiello explains. These effects have been demonstrated only in the laboratory, not in households and other real world environments, but Aiello believes that the few household studies may not have been long enough. “It’s very possible that the emergence of resistant species takes quite some time to occur…; the potential is there,” she says.

Apart from the potential emergence of drug-resistant bacteria in communities, scientists have other concerns about antibacterial compounds. Both triclosan and its close chemical relative triclocarban (also widely used as an antibacterial), are present in 60 percent of America’s streams and rivers, says environmental scientist Rolf Halden, co-founder of the Center for Water and Health at Johns Hopkins Bloomberg School of Public Health. Both chemicals are efficiently removed from wastewater in treatment plants but end up getting sequestered in the municipal sludge, which is used as fertilizer for crops, thereby opening a potential pathway for contamination of the food we eat, Halden explains. “We have to realize that the concentrations in agricultural soil are very high,” and this, “along with the presence of pathogens from sewage, could be a recipe for breeding antimicrobial resistance” in the environment, he says.

Triclosan has also been found in human breast milk, although not in concentrations considered dangerous to babies, as well as in human blood plasma. There is no evidence showing that current concentrations of triclosan in the human body are harmful, but recent studies suggest that it acts as an endocrine disrupter in bullfrogs and rats.

Further, an expert panel convened by the Food and Drug Administration determined that there is insufficient evidence for a benefit from consumer products containing antibacterial additives over similar ones not containing them.

“What is this stuff doing in households when we have soaps?” asks molecular biologist John Gustafson of New Mexico State University in Las Cruces. These substances really belong in hospitals and clinics, not in the homes of healthy people, Gustafson says.

Of course, antibacterial products do have their place. Millions of Americans suffer from weakened immune systems, including pregnant women and people with immunodeficiency diseases, points out Eugene Cole, an infectious disease specialist at Brigham Young University. For these people, targeted use of antibacterial products, such as triclosan, may be appropriate in the home, he says.

In general, however, good, long-term hygiene means using regular soaps rather than new, antibacterial ones, experts say. “The main way to keep from getting sick,” Gustafson says, “is to wash your hands three times a day and don’t touch mucous membranes.”

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Social networks illustrate how disease can spread

Social networks illustrate how disease can spread

By Anne Harding

NEW YORK (Reuters Health) – The best way to stop the next influenza pandemic in its tracks could be to shut down schools and keep students at home, according to the authors of a new study of social contact networks.

Based on the way they interact with one another, high school students “may form the local transmission backbone of the next pandemic,” Dr. Robert J. Glass of Sandia National Laboratories in Albuquerque, New Mexico, and his daughter, Laura M. Glass, suggest.

Networks for an entire community must be created to fully understand how to contain a potential epidemic, the senior Glass added in an interview. “With that kind of understanding you can then ask questions about where to target interventions,” he explained.

To develop the network described in the current study, the researchers surveyed elementary, middle and high school students about how and with whom they spent their time. Each person’s social network was characterized by the groups to which he or she belonged (such as the household, a class, or a sports team) along with the smaller network of person-to-person contacts within each of these groups.

The researchers then gathered information on the size of these groups, how many people a person was connected to within it, the amount of time he or she spent in the group, and the closeness of the contact a person had with individuals in that group.

They then evaluated the flu transmission potential of various contacts based on the degree of closeness and how much time a person spent in those contact activities.

Households, classes, groups of friends and sports teams all represented networks with “high potential for the transmission of influenza,” the researchers found. The older a child was, the more important outside connections became, with 75 percent of those in high school having social contacts outside the home conducive for transmitting influenza.

If it turns out that young people are a key route of influenza transmission within a community, closing schools and keeping children at home could help to shut down an epidemic, the researchers say. However, they add, similar studies in other groups within the community must be done to understand the other ways that the disease might spread.

“There are a whole bunch of things that you can learn from doing this kind of thing,” Glass noted. Networks can not only be used to study the spread of other types of disease, he added, but could also be used to identify individuals who are at-risk because they are less connected than others.

SOURCE: BMC Public Health, online February 14, 2008.

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