New Test For Deadly Fungal Infection In Patients With Damaged Immune Systems

A quicker, cheaper and more accurate test for deadly Aspergillus fumigatus fungal infections in patients with damaged or suppressed immune systems.

Fungal infections are a significant cause of death in patients whose immune systems are suppressed, for example those undergoing bone marrow transplantation or chemotherapy. Infection by breathing in the spores of the fungus Aspergillus fumigatus can cause Invasive Aspergillosis (IA) that can have a fatality rate approaching 90%. IA is very difficult to detect; doctors need to take tissue samples to see if the fungus is growing in the body.

As this is often not possible in very sick patients, tests that detect signature molecules of the fungus in patient's serum are used. These existing tests are costly, and require expertise and sophisticated laboratory facilities to run. They also cannot distinguish between molecules from the Aspergillus fungus and similar molecules from antibiotics and foodstuffs, and even certain bacteria.

Dr Thornton and colleagues have developed a test for IA using technology similar to that used in home pregnancy tests. The test uses a monoclonal antibody that binds to a glycoprotein antigen secreted specifically by Aspergillus species. It does not give a reaction with any other clinically important fungi. It only takes 15 minutes to perform, making it quicker and less costly than conventional laboratory-based tests.

"Because our test is user-friendly it can be used to diagnose IA at the 'point-of-care' for patients, said Dr Thornton, "it can be used to provide routine monitoring of patients at high-risk for the disease, such as bone marrow transplant recipients and leukaemia patients. We are currently working with a multinational clinical diagnostics company to develop a commercial version of the device."

Source:Sciencedaily

Fungi Can Tell Us About The Origin Of Sex Chromosomes

Fungi do not have sexes, just so-called mating types. A new study shows that there are great similarities between the parts of DNA that determine the sex of plants and animals and the parts of DNA that determine mating types in certain fungi. This makes fungi interesting as new model organisms in studies of the evolutionary development of sex chromosomes.

In the plant and animal kingdoms there are individuals of different sexes, that is, bearers of either many tiny sex cells (males) or a few large ones (females). In the third eukaryote kingdom (organisms with DNA gathered in the cell nucleus), the fungi kingdom, there are no sexes but rather a simpler and more primitive system of different so-called mating types. These are distinguished by different variants of a few specific genes.

There are many ways to determine sex. In humans it is done by sex chromosomes. It is thought that this sex difference arose in the plant and animal kingdom from the simpler system of mating types and that this happened several times independently of each other throughout evolution. The change is believed to have happened with the inhibition of a step in the copying process in DNA, which led to two separate chromosomes. These then developed further over a long period of time.

"In humans, sex chromosomes are believed to have developed over the last 300 million years from a common 'proto-sex chromosome,'" says Hanna Johannesson, who directed the study.

The new study shows for the first time that even though fungi do not have sexes, there are many similarities between the parts of the genome that determine sex in plants and animals and the parts of the genome that control mating types in certain fungi. The research group specifically studied a spore sac fungus (Neurospora tetrasperma) and can show that the similarities are great, regarding both present-day structure and the way in which it arose.

"It's hard to study the evolution of sex chromosomes, partly because so many different and important sex-specific characters are tied to them. But much of this can be avoided if we use simpler systems, like fungi, as models."

Source:ScienceDaily

Fungus Puts the Heat in Chili Peppers

There's a fungus among us chili fans—and some of the spicy peppers evolve their kick to repel it, a new study says.Chili peppers develop piquant chemicals to thwart the harmful microbes long enough to give birds and other animals a chance to disperse the pepper seeds, helping the chilies to procreate, scientists found.

Chilis high in chemicals called capsaicinoids occur most in areas where the fungus can enter the peppers through holes bored by insects, and these chilies are hotter, said study author Joshua Tewksbury, a biologist at the University of Washington in Seattle.

Gradient of Hotness

Tewksbury made the discovery after learning that some species of wild chilies in Bolivia have both pungent, spicy individuals and others that lack any kick whatsoever. "You can't tell them apart unless you chew on the fruits," he said.

Chewing on fruits—tough field work, Tewksbury joked—helped the team to establish a gradient of hotness along a 185-mile-long (300-kilometer-long) sample area in Bolivia. The northern end of the line is dominated by nonpungent chilies. The southern populations are much denser and hotter—really hot.

When the team examined fruits from along this transect, they found the pungent ones also had a greater concentration of scar damage from foraging insects similar to aphids and leaf hoppers. The skin on fruits, Tewksbury explained, is a first line of defense against microbes, which can't get past it on their own.

"Every time a bug pokes a hole in the chili fruit, the fungus can get in. And the more times the bugs can poke holes in the fruit, the more likely it is the fungus will start to invade," he said. Laboratory experiments showed capsaicinoids thwart the fungus invasion—but not the insects. "It looks like this chili is hot to stop the fungus, and the fungus is sort of mediated by these bugs," Tewksbury said.

Why Humans Eat Chilies

The finding, he said, adds weight to a hypothesis that humans first started to eat chilies for their antimicrobial properties. He noted that the majority of people who eat chilies live along the Equator, a region of the world where microbes also flourish and cause a range of intestinal diseases.

"We're simply co-opting the result of a very ancient evolutionary arms race between chilies and fungus and saying that will work for us too," he said.Linda Perry, an anthropologist at the Smithsonian Institution's National Museum of Natural History in Washington, D.C., said the new research clearly demonstrates that capsaicinoids evolved to thwart the fungus.

But the study does not show that capsaicinoids prevent foodborne illnesses or act as a preservative, said Perry, who is an expert on the domestication of chilies. Nor, she added, has it been demonstrated that the purported antimicrobial properties of chilies have much to do with their popularity. "I think people probably adopted chili peppers into their diet just because they taste good," she said.

Source: Nationalgeographic

Eye Ointment Can Cure Frog Fungus

An antibiotic primarily used to treat pinkeye in humans rids frogs of the fungal disease that is wiping out amphibian populations around the world, a team of New Zealand scientists reports.

Infected frogs treated with the drug for two weeks were cured of the deadly disease, called chytridiomycosis or frog chytrid disease.

The fungal disease, along with habitat destruction and global warming, is blamed for putting more than a third of the world's 6,234 known amphibian species on the path to extinction.Scientists have been racing to find a way to curb the disease before it takes an even heavier toll. The antibiotic chloramphenicol is "definitely the best" treatment found to date, Bishop said.

Another drug, itraconazole—which is used to treat fungal and yeast infections in humans—has also been shown to cure chytrid disease. But the drug causes kidney damage in some frogs, he noted.

Itraconazole also remains under patent protection and is therefore expensive, whereas chloramphenicol is generic and widely available.

Captive Tests

Allan Pessier is a veterinary pathologist at the San Diego Zoological Society in California and an expert on the deadly fungal disease. He said more tests are needed before declaring one drug better.

Both drugs, he added, are effective treatments for captive frogs but are probably never going to see widespread use in the wild as a spray or liquid dumped into streams and ponds.

"It's a step that helps us manage the disease, but it's not like declines associated with chytridiomycosis are going to go away because of this discovery," he said.

To be effective in the wild, scientists would need to overcome hurdles like maintaining sufficient concentrations of the drug in the environment without harming the ecosystem, he noted.

Bishop's colleague, biochemist Russell Poulter of Otago, stumbled upon chloramphenicol while running a battery of tests on various antibiotic and antifungal compounds in search of any that may prove effective against chytrid disease.

"It was a very surprising result to find an antibacterial that killed a fungus," Bishop said.

The researchers used the compound both as an over-the-counter ointment applied to infected frogs' skin and as a solution soaked into a paper towel on which the frogs sat.

"We found that after about 18 days we could swab the frogs again and they would be cured of chytrids," Bishop said.

The team tested the compound on three species in New Zealand: the brown tree frog and the southern bell frog—which were introduced from Australia—and the critically endangered native Archey's frog.

Bishop said all the frogs are still alive and well 12 months after treatment. Researchers at the Taronga Zoo in Sydney, Australia, are now testing the drug on six more endangered frog species.

Why the drug kills the fungus, he added, remains under investigation.

Drug Resistance?

The New Zealand researchers also tried to re-infect frogs that had been successfully treated. The frogs again contracted the disease, but it disappeared within a few days.

Bishop is uncertain why the frogs were "difficult to re-infect." Perhaps the chloramphenicol lingers in their skin or it works like a vaccine, priming the amphibian immune system to thwart the fungus, he said.

"We're hoping this is going to be something really significant, and we are currently investigating that," he added.

Reid Harris is a biologist at James Madison University in Harrisonburg, Virginia, who studies chytrid disease. He agreed further studies are needed to investigate the apparent disease resistance.

"The more we can learn about any sort of mechanism of resistance ... the better," he said.

Conserving Frogs

Bishop and his colleagues are continuing to comb through various antifungal agents in search of one that is effective against chytrid disease.

Antifungals, he noted, may prove more acceptable to spraying in the wild than chloramphenicol or itraconazole.

"People don't want antibiotics being dumped in vast quantities in the environment," he said.

Meanwhile, Pessier of the Zoological Society of San Diego said the antibiotics can be used to treat and maintain captive populations until a solution to the problem in the wild is found.

"If you didn't have that option," he said, "you'd see frogs going essentially extinct because of the infection."

Source:National Geographic