Showing posts with label antibiotic resistant. Show all posts
Showing posts with label antibiotic resistant. Show all posts

Thursday, March 19, 2015

New version of common antibiotic could eliminate risk of hearing loss

"All I remember is coming out of treatment not being able to hear anything," said Bryce, now a healthy 14-year-old living in Arizona. "I asked my mom, 'Why have all the people stopped talking?'" He was 90 percent deaf.

"The loss has been devastating," said his father, Bart Faber. "But not as devastating as losing him would have been."
Treatment with aminoglycosides, the most commonly used class of antibiotics worldwide, is often a lifesaving necessity. But an estimated 20-60 percent of all patients who receive these antibiotics suffer partial or complete hearing loss.
Now, in a study that will be published online Jan. 2 in the Journal of Clinical Investigation, researchers at the Stanford University School of Medicine report that they have developed a modified version of an aminoglycoside that works effectively in mice without the risk of causing deafness or kidney damage, another common side effect.
The researchers hope to test versions of the modified antibiotic in humans as soon as possible.
"If we can eventually prevent people from going deaf from taking these antibiotics, in my mind, we will have been successful," said Anthony Ricci, PhD, professor of otolaryngology-head and neck surgery and co-senior author of the study. "Our goal is to replace the existing aminoglycosides with ones that aren't toxic."
Four years in the making
It took the scientists four years of research to produce 5 grams of the newly patented antibiotic, N1MS, which is derived from sisomicin, a type of aminoglycoside.
N1MS cured urinary tract infection in mice just as well as sisomcicin, but did not cause deafness, study results show. The study presents a promising new approach to generating a new class of novel, nontoxic antibiotics, Ricci said.
The two senior authors -- Ricci and Alan Cheng, MD, associate professor of otolaryngology-head and neck surgery -- joined forces in 2007 to explore the idea of creating new and improved versions of these antibiotics based on a simple yet groundbreaking idea born of Ricci's basic science research into the biophysics of how hearing works within the inner ear.
"It's a nice example of how basic science research is directly translatable into clinical applications," said Ricci.
Ricci is an expert on the process by which sound waves open ion channels within the sensory hair cells of the inner ear, allowing their conversion to electrical signals that eventually reach the brain.
Because aminoglycosides cause deafness by killing these nonregenerating hair cells, Ricci postulated, why not simply make the drug molecules unable to enter the cells' channels?
The idea made sense to Cheng.
"As a clinician-scientist, I treat kids with hearing loss," Cheng said. "When a drug causes hearing loss it is devastating, and it's especially disturbing when this happens to a young child as they rely on hearing to acquire speech.
"When I came to Stanford seven years ago from the University of Washington, I was exploring the angle that maybe we could add drugs to protect the ear from toxicity. Tony brought up this new idea: Why don't we just not let the drug get in? Great idea, I thought. When do we start to work?"
A potent antibiotic
For 20 years, and despite newer, alternative antibiotics, aminoglycosides have remained the mainstay treatment worldwide for many bacterial diseases, including pneumonia, peritonitis and sepsis. They also are often used when other antibiotics have failed to treat infections of unknown origins.
Their popularity is due, in part, to their low cost, lack of need for refrigeration and effectiveness at treating bacterial infections at a time when the declining potency of antibiotics is a major public health concern. They are frequently used in neonatal intensive care units to battle infections, or even the threat of infections, which pose a life-threatening risk for babies. Exactly how many premature babies suffer hearing loss as a side effect of treatment with the drug is unknown, Ricci said.
"The toxicity of these drugs is something we accept as a necessary evil," said Daria Mochly-Rosen, PhD, director of SPARK, a program at Stanford that assists scientists in moving their discoveries from bench to bedside.

Ref :

Tuesday, March 17, 2015

Honey offers new approach to fighting antibiotic resistance ............

In continuation of my update on Honey..

Honey, that delectable condiment for breads and fruits, could be one sweet solution to the serious, ever-growing problem of bacterial resistance to antibiotics, researchers said in Dallas* today. Medical professionals sometimes use honey successfully as a topical dressing, but it could play a larger role in fighting infections, the researchers predicted.

"The unique property of honey lies in its ability to fight infection on multiple levels, making it more difficult for bacteria to develop resistance," said study leader Susan M. Meschwitz, Ph.D. That is, it uses a combination of weapons, including hydrogen peroxide, acidity, osmotic effect, high sugar concentration and polyphenols -- all of which actively kill bacterial cells, she explained. The osmotic effect, which is the result of the high sugar concentration in honey, draws water from the bacterial cells, dehydrating and killing them.

In addition, several studies have shown that honey inhibits the formation of biofilms, or communities of slimy disease-causing bacteria, she said. "Honey may also disrupt quorum sensing, which weakens bacterial virulence, rendering the bacteria more susceptible to conventional antibiotics," Meschwitz said. Quorum sensing is the way bacteria communicate with one another, and may be involved in the formation of biofilms. In certain bacteria, this communication system also controls the release of toxins, which affects the bacteria's pathogenicity, or their ability to cause disease.

Meschwitz, who is with Salve Regina University in Newport, R.I., said another advantage of honey is that unlike conventional antibiotics, it doesn't target the essential growth processes of bacteria. The problem with this type of targeting, which is the basis of conventional antibiotics, is that it results in the bacteria building up resistance to the drugs.

Honey is effective because it is filled with healthful polyphenols, or antioxidants, she said. These include the phenolic acids, caffeic acid, p-coumaric acid and ellagic acid, as well as many flavonoids. "Several studies have demonstrated a correlation between the non-peroxide antimicrobial and antioxidant activities of honey and the presence of honey phenolics," she added. A large number of laboratory and limited clinical studies have confirmed the broad-spectrum antibacterial, antifungal and antiviral properties of honey, according to Meschwitz.

She said that her team also is finding that honey has antioxidant properties and is an effective antibacterial. "We have run standard antioxidant tests on honey to measure the level of antioxidant activity," she explained. "We have separated and identified the various antioxidant polyphenol compounds. In our antibacterial studies, we have been testing honey's activity against E. coliStaphylococcus aureus and Pseudomonas aeruginosa, among others."

Friday, October 17, 2014

'Programmable' antibiotic harnesses an enzyme to attack drug-resistant microbes

Rockefeller University researchers colonized mouse skin with a mix of bacterial cells, some resistant to the antibiotic kanamycin. They made the resistant cells glow (left) and treated the mix with an enzyme that targeted and killed off most resistant cells (right).

Conventional antibiotics are indiscriminate about what they kill, a trait that can lead to complications for patients and can contribute to the growing problems of antibiotic resistance. But a a 'programmable' antibiotic would selectively target only the bad bugs, particularly those harboring antibiotic resistance genes, and leave beneficial microbes alone.

Researchers at Rockefeller University and their collaborators are working on a smarter antibiotic. And in research to be published October 5 in Nature Biotechnology, the team describes a 'programmable' antibiotic technique that selectively targets the bad bugs, particularly those harboring antibiotic resistance genes, while leaving other, more innocent microbes alone.
"In experiments, we succeeded in instructing a bacterial enzyme, known as Cas9, to target a particular DNA sequence and cut it up," says lead researcher Luciano Marraffini, head of the Laboratory of Bacteriology. "This selective approach leaves the healthy microbial community intact, and our experiments suggest that by doing so you can keep resistance in check and so prevent certain types of secondary infections, eliminating two serious hazards associated with treatment by classical antibiotics."
The new approach could, for instance, reduce the risk of C. diff, a severe infection of the colon, caused by the Clostridium difficile bacterium, that is associated with prolonged courses of harsh antibiotics and is a growing public health concern.
The Cas9 enzyme is part of a defense system that bacteria use to protect themselves against viruses. The team coopted this bacterial version of an immune system, known as a CRISPR (clustered regularly interspaced short palindromic repeats) system and turned it against some of the microbes. CRISPR systems contain unique genetic sequences called spacers that correspond to sequences in viruses. CRISPR-associated enzymes, including Cas9, use these spacer sequences as guides to identify and destroy viral invaders.
The researchers were able to direct Cas9 at targets of their choosing by engineering spacer sequences to match bacterial genes then inserting these sequences into a cell along with the Cas9 gene. The cell's own machinery then turns on the system. Depending on the location of the target in a bacterial cell, Cas9 may kill the cell or it may eradicate the target gene. In some cases, a treatment may prevent a cell from acquiring resistance, they found.
"We previously showed that if Cas9 is programmed with a target from a bacterial genome, it will kill the bacteria. Building on that work, we selected guide sequences that enabled us to selectively kill a particular strain of microbe from within a mixed population," says first author David Bikard, a former Rockefeller postdoc who is now at the Pasteur Institute in Paris.