Antibiotic Resistance: Beginning of the End?

By Lila Abassi — Dec 01, 2015
Antibiotic resistance and the possibility of approaching the end of the antibiotic era sounds fairly apocalyptic. A recent study reveals a new gene, MCR-1, that allows for a common bug, Eschirichia coli, to become resistant to polymyxin antibiotics. These are the last line of defense against infections with E. coli. This has pandemic potential.

Short of being -- what I like to call -- a "devastationary," the idea of antibiotic resistance and the possibility of approaching the end of the antibiotic era sounds fairly apocalyptic.

A study published in the Lancet Infectious Diseases Journal reveals a new gene, called MCR-1 that allows for a common bug, Eschirichia coli to become resistant to polymyxin antibiotics -- mainly colistin -- which is the last line of defense against infections with E. coli. This has pandemic potential.

According to the World Health Organization, patients that have infections caused by antibiotic resistant organisms are faced with increased risk of worse clinical outcomes and death, and consume more health-care resources than patients infected with the same bacteria that are not resistant.

Since their inception about 70 years ago, antibiotics have reduced illness and death from infectious causes. Its rampant use, as well as inappropriate prescribing, dosing and duration of use, have led to the development of bacteria that evade being killed, thus making them tougher and tougher to treat. Antibiotics have also been used in the feeds of food-producing animals that add to the resistance problem. Additionally, antibiotic resistance can be spread person-to-person (i.e. in hospitals) or from other environmental sources.

In 2012, the WHO designated polymyxins as critically important for human use. It would make absolute sense to restrict their use, especially in light of them being a last resort antibiotic, from agricultural use. However, in China, polymyxin antibiotics are more in use in animals than they are in humans.

We needed to have definitive borders between antibiotics that are used in human medicine and those that are used in the veterinary sector, said Timothy Walsh, a medical microbiologist from Cardiff University in Wales, and one of the authors of the study. He is scheduled to meet with the Chinese government to encourage the ban of agricultural use of polymyxins.

Chinese and British scientists involved in the study discovered that the mode of resistance in E. coli is conferred via transfer of the resistance gene in plasmids, which are small, circular strands of DNA. What makes this feature particularly worrisome is that the transfer of resistance can occur not only among E. coli bacteria, but also to entirely different bacterial species such as Klebsiella pneumonia and Pseudomonas aeruginosa.

The researchers conducted a survey where they found the resistance gene in 166 of 804 pigs tested, and 78 of 523 raw meat samples. Additionally, a small number of hospitalized patients in China, representing 1 percent of 1,322 samples, also had the resistance gene.

These are extremely worrying results. The polymyxins (colistin and polymyxin B) were the last class of antibiotics in which resistance was incapable of spreading cell to cell. Until now, colistin resistance resulted from chromosomal mutations, making the resistance mechanism unstable and incapable of spreading to other bacteria, says Liu Jian-Hua, a professor at China s Southern Agricultural University, Guangzhou, and a co-author of this study.

This means that the resistant strain could have epidemic potential and suggests the progression from extensive drug resistance to pandrug resistance is inevitable, according to the scientists.

This study highlights the increasing difficulty of treating infections, stresses the importance of improved surveillance methods to track the spread of resistant strains of bacteria and the necessity to minimize or eliminate, if possible, the use of antibiotics in agriculture. Additionally, further research into non-antibiotic treatments of infectious processes would be of tremendous value.

For the optimists or non-devastationaries, I would like to refer to Dr. Jean Patel, the acting director of the office of antimicrobial resistance at the Centers for Disease Control and Prevention, who said, just because something has the potential to spread doesn t always mean that it will.

There are other similar examples of plasmid-mediated resistance that led to dire predictions, and they were proved wrong.