miércoles, 23 de noviembre de 2016

Parasites, Potatoes, and Polution - Antimicrobial Resistance in a One Health World

23 November 2016 
Dear Colleagues,
Last week was World Antibiotic Awareness Week, a WHO campaign to help raise awareness and understanding of one of the biggest threats to global health, food security, and development today - the overuse and misuse of life-saving drugs.
Three recent ProMED posts illustrate the contours of the problem. One discusses recent studies that were looking to find molecular markers for resistance to piperaquine, a drug used in artemisinin combination therapies. As malaria in the Greater Mekong sub-region becomes increasingly resistant to artemisinin and the partner drugs that are used to treat the P. falciparumparasite, molecular markers are urgently needed to help monitor the spread of resistance and recommend alternative treatments. Malaria in Cambodia, Thailand, and Myanmar is showing decreased susceptibility to the artemisinins which are combined with piperaquine. If the malaria parasite becomes resistant to piperaquine, the remaining option of artemisinin monotherapy will facilitate development of resistance and result in treatment failure.
The second post reported on a study of a mutant of  Alternaria solani, the fungus causing early blight on potato and other solanaceous crops that has become increasing resistant to the family of chemicals commonly used against the disease. Themselves derived from fungi, strobilurins are considered environmentally safe. But like many other fungicides, they have single-site activity; the target pathogens are likely to develop resistance or tolerance over time. Since they are used against most major fungal crop diseases, pathogen resistance is of major concern worldwide. Similar to the application of combination therapies in humans, rotating or mixing chemical classes of fungicides extends the useful life of the compounds.
A third post described the situation in Medak, India, a district of about 2.5 million that has become one of the world's largest suppliers of cheap drugs. Community activists, researchers, and some drug company employees say the presence of more than 300 drug firms, combined with lax oversight and inadequate water treatment, has left lakes and rivers laced with antibiotics, "making this a giant Petri dish for antimicrobial resistance."
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Antibiotics are produced naturally by various microbes that inhibit or kill other microbes in their immediate environment and these other microbes in their immediate environment would have developed resistance to these antimicrobial compounds, otherwise they would not have survived. So, it is not surprising that a team from the California Polytechnic State University reportedly found antibiotic resistance genes in human feces from ancient 11th century Incan mummies ( http://www.ndtv.com/world-news/antibiotic-resistant-genes-discovered-in-11th-century-mummy-1235286 ), almost 1000 years before Sir Alexander Fleming discovered penicillin in 1928. Before the 1950s, however, the selective pressure exerted by the presence of antibiotics occurred only within the immediate vicinity of the antibiotic-producing organisms.

Now, antibiotics are being produced on a massive scale. Between 2000 and 2010, total global antibiotic consumption is reported to have grown by more than 30 per cent ( https://cddep.org/sites/default/files/swa_2015_final.pdf ). The greatest increase in antibiotic use has been in low- and middle-income countries, where there has been increasing prosperity leading to increased demand. 80 per cent of human use is occurring in the community, either prescribed by healthcare providers or purchased directly without prescriptions (https://cddep.org/sites/default/files/swa_2015_final.pdf), but the CDC estimates that, at least in the US, 30 per cent of antibiotic prescriptions are unnecessary. ( http://www.cdc.gov/media/releases/2016/p0503-unnecessary-prescriptions.html).

Similarly, increasing prosperity has led to increasing demand for animal protein, which has led to intensive food animal production and the consequent greater use of antibiotics for prevention of infection and growth promotion of these food animals. More than 70 per cent of the antibiotics used in the US are for animal husbandry. ( http://www.pewtrusts.org/~/media/legacy/uploadedfiles/phg/content_level_pages/issue_briefs/hhifibrecommendationsforfdafactsheetpdf.pd ).

The increasing use of antibiotics in both human and veterinary practice and their careless discharge, often accompanied by antibiotic resistance genes, into the environment in pharmaceutical industrial, farm, and human waste have contributed to the increasing presence of antibiotics in the environment. Although human and food animal consumption of antibiotics exerts selective pressure on microbial communities that reside in or on their bodies, the increasing presence of antibiotics and antibiotic resistance genes in the environment can possibly exert selective pressure on microbial populations outside the body, but this requires further study. http://jac.oxfordjournals.org/content/52/1/5.full, http://www.sciencedirect.com/science/article/pii/S0269749109002942 , and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4034546/. 

For twenty-two years, ProMED has alerted the international infectious disease community to the dangers of antimicrobial resistance and other urgent topics. But, to continue to do this every day, ProMED needs your financial support. Please contribute generously.

Thank you.
Matt Levison, MD
ProMED-mail Associate Editor and Bacterial Disease Moderator Professor of Public Health Drexel University School of Public Health

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