Superbug resistant to last resort antibiotic


The emergence of the first strain of bacteria resistant to colistin is causing alarm among health professionals. Bill Condie reports.


A coloured scanning electron micrograph shows E. coli bacteria, a new strain of which is resistant to all known antibiotics.
PASIEKA
A patient has become the first in the US with an infection resistant to colistin – the antibiotic of last resort used to treat infections that have not responded to anything else.

The so-called “superbug” is a strain of E. coli that could be the harbinger of pathogens resistant to all treatment.

The case – a urinary tract infection of a 49-year-old Pennsylvania woman – was reported in Antimicrobial Agents and Chemotherapy, a publication of the American Society for Microbiology.

The study by the Walter Reed National Military Medical Center has alarmed health officials.

“We risk being in a post-antibiotic world,” Thomas Frieden, director of the US Centers for Disease Control and Prevention, told Reuters.

“The more we look at drug resistance, the more concerned we are. The medicine cabinet is empty for some patients. It is the end of the road for antibiotics unless we act urgently.”

The study explains that the superbug itself had first been infected with a tiny piece of DNA called a plasmid, which passed along a gene called mcr-1 that confers resistance to colistin.

“This heralds the emergence of truly pan-drug resistant bacteria,” said the study.

“To the best of our knowledge, this is the first report of mcr-1 in the USA.”

The mcr-1 gene was found last year in people and pigs in China and doctors are worried about the potential for the superbug to spread from animals to people.

“It is dangerous and we would assume it can be spread quickly, even in a hospital environment if it is not well contained,” Gail Cassell, a microbiologist and senior lecturer at Harvard Medical School, told Reuters.

Experts have warned of this potential problem since the 1990s thanks, in part, to the overprescribing of antibiotics and their extensive use in food livestock.

Extensive use of antibiotics in intensive farming is partly to blame for increased drug resistance in humans.
MARTIN HARVEY
How did we come to this?

In 1948, an American biochemist, Thomas H. Jukes, discovered that the addition of a cheap antibiotic to the diet of chickens made them gain weight much faster than normal.

His company, Lederle, lost no time in rolling out the product as an agricultural supplement, effectively setting in train a vast uncontrolled experiment to transform the food chain.

Now, nearly 70 years later, about 80% of antibiotic sales in the US go to livestock production rather than to human health care, despite the mounting evidence that drug resistance spills over from livestock to people.

To read more about how this came about and the risks it poses, see How did antibiotics become part of the food chain?

Some of the biggest effects of multi drug resistance are being felt by patients with tuberculosis. The problem is particularly acute in countries such as South Africa, where patients carrying drug-resistant TB strains are routinely returned to their communities.

TB is the leading cause of death in South Africa thanks to the large number of people co-infected with HIV.

For Extreme Drug Resistant TB, cure rates are now just 20% nationally.

For more, read The TB time bombs.

  1. https://cosmosmagazine.com/life-sciences/how-did-antibiotics-become-part-food-chain
  2. https://cosmosmagazine.com/life-sciences/tb-time-bombs
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