Mouse study links triclosan, a common antimicrobial, to colonic inflammation

A large research team led by senior author Guodong Zhang at the University of Massachusetts Amherst reports that the antimicrobial ingredient triclosan, found in hand soaps and toothpastes among other products, could have adverse effects on colonic inflammation and colon cancer by altering gut microbiota, the microbes found in our intestines.

The study reported in Science Translational Medicine suggests that short-time treatment with low-dose triclosan caused low-grade colonic inflammation, and exaggerated disease development of colitis and colitis-associated colon cancer in mice, Zhang says. "These results, for the first time, suggest that triclosan could have adverse effects on gut health," he notes.

Co-first authors Haixia Yang and Weicang Wang, both from the Zhang laboratory in the food science department at UMass Amherst, point out that triclosan is among the most widely used antimicrobial ingredients and is found in more than 2,000 consumer products. They note that a National Health and Nutrition Examination Survey showed that triclosan was detected in about 75 percent of the urine samples of individuals tested in the United States and it is among the top ten pollutants found in U.S. rivers.

"Because this compound is so widely used, our study suggests that there is an urgent need to further evaluate the impact of triclosan exposure on gut health in preparation for the potential establishment of further regulatory policies," says Yang, a postdoctoral fellow in Zhang laboratory.

In this study, the 21-member team that included 12 UMass Amherst researchers, investigated the effects of triclosan on colonic inflammation and colon cancer using several mouse models. In all mouse models tested, triclosan promoted colonic inflammation and colon tumorigenesis, Zhang reports.

His co-author, food scientist Hang Xiao, adds, "In particular, we used a genetically engineered mouse model which develops spontaneous inflammatory bowel disease or IBD. Also, treatment with triclosan significantly increased disease development of IBD in the mice, suggesting that IBD patients may need to reduce exposure to this compound."

In a series of experiments designed to explore mechanisms, the research team found that gut microbiota is critical for the observed adverse effects of triclosan. Feeding triclosan to mice reduced the diversity and changed the composition of the gut microbiome, a result similar to what was observed in a human study conducted by others, Zhang says.

Also, triclosan had no effect in a germ-free mouse model where there is no gut microbiome present, nor in a genetically engineered mouse model where there is no Toll-like receptor 4 (TLR4) - an important mediator for host-microbiota communications. "This is strong evidence that gut microbiota is required for the biological effects of triclosan" Zhang points out.

In an editorial note accompanying the article, the journal says, "Triclosan exposure is practically unavoidable in the United States, but little is known how ingestion may affect our health." This study observed that triclosan altered mouse gut microbiota, increased inflammation, increased the severity of colitis symptoms and spurred colitis-associated colon cancer cell growth. Though limited to mouse models, "this work suggests that the effects of triclosan on human health should be examined more closely," editors noted.

Ref : http://www.umass.edu/newsoffice/article/triclosan-common-antimicrobial-ingredient

http://stm.sciencemag.org/content/10/443/eaan4116

Antimicrobial copper surfaces reduce risk of acquiring hospital infection

Antimicrobial copper surfaces reduce risk of acquiring hospital infection

Plectasin - a new weapon against highly resistant microbes ?..

We know that Plectasin, found in Pseudoplectania nigrella (see picture), is the first defensin to  be isolated from a fungus. Plectasin has a chemical structure resembling defensins found in spiders, scorpions, dragonflies and mussels. In laboratory tests, Plectasin was especially active in inhibiting the growth of the common human pathogen Streptococcus pneumoniae, including strains resistant to conventional antibiotics. Plectasin has a low toxicity in mice, and cured them of peritonitis and pneumonia caused by S. pneumoniae as efficiently as vancomycin and penicillin, suggesting that it may have therapeutic potentia.

Now researchers lead by Prof. Dr. Hans-Georg Sahl of   Universities of Bonn, Utrecht, Aalborg and of the Danish company Novozymes AS have shed light on how the substance Plectasin,  destroy highly resistant bacteria. As per the claim by the researchers Plectasin binds to a cell-wall building block called lipid II and thus prevents it from being incorporated and thus disrupting the forming of the cell wall in bacteria so that the pathogens can no longer divide. 

In this process, plectasin behaves like a thief which steals the stones off a mason. 'It binds to a cell-wall building block called lipid II and thus prevents it from being incorporated ,' Professor Sahl explains. 'However, bacteria cannot live without a cell wall.' It comes as no surprise that the most famous antibiotic penicillin also inhibits cell-wall synthesis...

Researchers claims that, plectasin is more similar in its mode of action to another widely used drug, vancomycin. Vancomycin had been the drug of choice in combating MRSA strains since the 1980s. Meanwhile, though, there are more and more bacteria that are also resistant to vancomycin. 'However, these strains are still susceptible to plectasin,' Dr. Tanja Schneider emphasises. Nevertheless, there is no permanent solution to the resistance problem even with a new antibiotic . 'It is always just a question of time until the pathogens mutate and become insensitive ,' she says. 'It's a never ending arms race..' authors conclude that plectasin will be promising lead compound for new antibiotics...

Ref : http://www.sciencemag.org/cgi/content/abstract/328/5982/1168

New Data on NovaBay’s Aganocide compounds ( first-in-class anti-infectives) as presentations...

NovaBay Pharmaceuticals, Inc.  recently announced that, it is will be  presenting the latest public data on its Aganocide^® compounds (see structures : a new class of broad-spectrum antimicrobials). 

Data will be presented during three poster sessions at the Association for Research in Vision and Ophthalmology (ARVO) annual meeting in Fort Lauderdale, Florida. NovaBay's Aganocide compounds are first-in-class anti-infectives being developed for the treatment and prevention of antibiotic-resistant infections. NovaBay and Alcon, Inc., the world's leading eye care company, have a licensing and research collaboration agreement for the use of NovaBay's Aganocide compounds in the eye, ear and sinus, and for contact lens care.

The three presentations are :

1. Dichloro analog (AL-46383A) (see structure) as a Novel Topical Ophthalmic Agent, 2. In vitro evaluation of dichloro analog as an Antiviral Agent Against Adenovirus and HSV-1 and 3. topical dichloro analog,  Inhibits Adenovirus Replication in the Ocular Ad5/NZW Rabbit Replication Model.

NVC-422, or AL-46383A, is a stable compound based on the chemical structures of N-chlorotaurine (NCT) and N,N-dichlorotaurine, which are naturally occurring antimicrobial agents produced by the body's white blood cells to fight invasive pathogens.

Alcon is conducting a Phase 2 clinical trial of this compound for the treatment of viral conjunctivitis, a form of "pink eye". The randomized, placebo-controlled trial is enrolling approximately 250 patients at more than 30 medical centers in the United States and worldwide. It is designed to determine the safety and efficacy of NVC-422 or AL-46383A. 

Ref : http://www.novabaypharma.com/investors/release/apr_30_2010

New insight for design of novel antibiotic derivatives for drug resistant microorganisms...

Viomycin and Capreomycin (a group of nonribosomal peptide antibiotics) belong to the tuberactinomycin (an essential component in the drug cocktail currently used to fight infections of Mycobacterium tuberculosis) Are among the most effective antibiotics against multidrug-resistant tuberculosis. Viomycin was the first member of the tuberactinomycins to be isolated and identified and was used to treat TB until it was replaced by the less toxic, but structurally related compound, Capreomycin. The tuberactinomycins target bacterial ribosomes, binding RNA and disrupting bacterial protein biosynthesis.

Now Dr. Steitz and his colleagues at Yale's Department of Molecular Biophysics and Biochemistry, have identified two structures of tuberactinomycins bound to the ribosome. The researchers claims that,   the identification of these structures provides an insight for the design of novel antibiotic derivatives that could be effective against a variety of drug resistant microorganisms.

As per the claim by Dr.Steitz, both antibiotics (Viomycin and Capreomycin) bind to the same site on the ribosome, which lies at the interface between helix 44 of the small ribosomal subunit and helix 69 of the large ribosomal subunit. The structures of these complexes suggest that the tuberactinomycins inhibit translocation by stabilizing the tRNA in the A site in the pretranslocation state. In addition, these structures show that the tuberactinomycins bind adjacent to the binding sites for the paromomycin and hygromycin B antibiotics, which may enable the development of new derivatives of tuberactinomycins that are effective against drug-resistant strains. The authors have presented two crystal structures of the 70S ribosome in complex with three tRNAs and bound to either viomycin or capreomycin at 3.3-and 3.5-Å resolution, respectively in "Nature Structural & Molecular Biology 14 February 2010 ".

Interestingly, Dr. Steitz was awarded the 2009 Nobel Prize in Chemistry   for his groundbreaking work determining a high resolution crystal structure of the 50S subunit of the ribosome which has proved to be a major target for antibiotic development.

Hope this discovery will lead to a new insight for design of novel antibiotic derivatives that could be effective against a variety of drug-resistant microorganisms ....

Ref: http://www.rib-x.com/news_and_events/release_2010_02_16

Bromo furanones a new class of antimicrobials.....

We know that Candida albicans is the most virulent  Candida species of medical importance, which presents a great threat to immunocompromised individuals such as HIV patients. Candida albicans is carried by about 75 percent of the public. Typically the fungus is harmless but, in individuals with HIV or otherwise compromised immune systems, it can cause candidiasis, which has a high mortality rate. The fungi can also form biofilms that attach to surfaces and are up to 1,000 times more resistant to anti-fungals.

Currently, there are only four classes of antifungal agents available for treating fungal infections: azoles (Diflucan, flucanazole), polyenes, pyrimidines, and echinocandins. The fast spread of multidrug resistant C. albicans strains has increased the demand for new antifungal drugs.

Now two Syracuse University scientists have developed new brominated furanones (see structure) that exhibit powerful anti-fungal properties.

As per the claim by the researchers, the compound exhibited more than 80 percent. Structure and activity of this class of furanones reveals that the exocyclic vinyl bromide conjugated with the carbonyl group is the most important structural element for fungal inhibition. Furthermore, gene expression analysis using DNA microarrays showed that 3 μg/mL of 4-bromo-5Z-(bromomethylene)-3-butylfuran-2-one (BF1) upregulated 32 C. albicans genes with functions of stress response, NADPH dehydrogenation, and small-molecule transport, and repressed 21 genes involved mainly in cell-wall maintenance.

Interestingly, only a small overlap is observed between the gene expression changes caused by the representative brominated furanone in this study and other antifungal drugs reported in literature. This result suggests that brominated furanones and other antifungal drugs may target different fungal proteins or genes.

The existence of such new targets provides an opportunity for developing new agents to control fungal pathogens which are resistant to currently available drugs.

The research team has also shown previously that these furanones inhibit bacterial biofilm formation; thus they may help control chronic infections where biofilms often appear, on surgical, dental and other implants. Hope broad spectrum of other potential capabilities make this class of compounds a new way to combat the microbes in the days to come...

Ref : http://springerlink.com/content/92735526v5013088/