Rethinking The Strategies For Fighting Antibiotic Resistance

2010-06-20 | |
Last updated: 2010-06-20

Since the discovery of antibiotics in 1928, an arms race of sorts has been underway between our bacterial adversaries and us. The creation of the antibiotic penicillin was only the first in a series of developments to create more effective ways of halting bacterial infections by killing off these bacterial invaders. However, as we have advanced so have they and so in an attempt to gain a clearer advantage, medical science is shifting towards different strategies to battle bacterial infections.

And, it is about time for such changes in strategy as it seems that wherever researchers take a look, they find strains of antibiotic resistant bacteria thriving. Such bad bugs have been discovered in the houseflies of fast food restaurants and food handling facilities as well as in employees of the poultry industry who are at 32 times the risk of carrying antibiotic resistant bacteria E. Coli.

These bacteria are in no way limited to these higher risk locations either. Fertilizers made from sewage sludge have helped to spread the bacteria to potentially threaten our food supplies. Researchers with the Swedish National Veterinary Institute found that roughly 80% of the sewage solids collected from water treatment plants contained bacteria that were resistant to the Vancomycin antibiotic. Vancomycin is often called the “antibiotic of last resort” because it is only typically used when other antibiotics fail.

These findings are not isolated either as research conducted at Newcastle University found antibiotic resistant bacteria in almost 80% of the soil samples taken from numerous locations around the Netherlands. With so much of the human environment contaminated with these super bacteria, the risk of human infection becomes far higher.

Even in the greater environment, researchers are seeing antibiotic resistant bacteria. Researchers from a collection of universities including the University of Florida found sharks and red fish containing bacteria that were resistant to as many as 13 different forms of antibiotic. Only in the far reaches of the Artic where polar bears rarely interact with humans have researchers from the University of Tromso found little evidence of antibiotic resistant bacteria in bear droppings.

Clearly, our current methods for using antibiotics are contributing to the evolution of super bugs.

However, as published in a paper by the American Academy of Microbiology, antibiotic misuse is not the only reason that super bugs are evolving. In part, poor hygiene and sanitation in even first world countries enables the few bacteria that survive an antibiotic assault with the opportunity to reproduce into large antibiotic resistant populations. Likewise, insufficient processing of antibiotic-contaminated human waste provides bacteria in the wild with “intelligence”. Such information can enable the bacteria to adapt to the arsenal that we are using against them.

Based on the growing threat of antibiotic resistant bacteria and the newfound understanding as to why the bacteria are gaining against medical science, researchers are now looking at other approaches to fight the battle. The new approaches are less about making a deadlier antibiotic and more about preventing the bacteria from adapting.

In efforts at the Canadian Institutes for Health Research (CIHR), scientists have finally determined that bacteria develop resistance to Vancomycin by detecting the drug itself. This knowledge means that future versions of the antibiotic could limit the development of resistance by masking the “signature” of the antibiotic from the sensors of the bacteria. In short, with delivery of “stealth” versions of antibiotics, the bugs would never know what hit them.

This is but one strategy that is required, however because bacteria never put all their eggs in one basket. Bacterial colonies instead keep what are called “persister” cells that remain dormant for random and long periods of time. These cells are in a sort of dormant state so are not affected by antibiotics because they are not actively consuming chemicals from the environment.

To destroy these cells, a different approach is required for antibiotic delivery according to researchers from Virginia Tech. Such an approach involves understanding the approximate frequency when the “persister” cells for a particular species of bacteria will become active. With this intelligence in mind, the timed delivery of antibiotics can destroy far more of the “waking” “persister” cells to prevent a gain by the infection and the development of resistance. For those of us popping the antibiotic pills, this could mean taking the pills for a longer duration but not every day.

Ultimately, the best approaches to preventing antibiotic resistance are those that can be used on an ongoing basis. With this mind, researchers from Harvard University found from studies that overall killing effect is not the best measurement of ongoing antibiotic effectiveness. Instead, they are looking at antibiotic combinations that work more poorly in combination than they do individually. Their hope is to use the approach to stop bacterial evolution in its tracks.

By treating the infection with a combination that is less effective than either of the drugs on its own, more bacteria that are sensitive to the antibiotic combination will survive than will those that adapt to one antibiotic. This then allows the antibiotic-sensitive bacteria to outbreed and out compete any bacteria that adapt to either of the drugs individually. In essence, the resistant bacteria are driven to extinction through the normal process of evolution.

These researchers are now seeking other combinations of existing antibiotics with reduced combined effectiveness to halt the advances of antibiotic resistant bacteria.

With some antibiotic resistant bacterial infections taking more than 18,000 lives per year, more lives than HIV/AIDs in the US, antibiotic resistance is a problem desperately in need of new strategies. While development of new drugs in the arsenal is still very important, it is more important to ensure that the use of existing antibiotics be optimized to minimize the possibilities for bacteria to adapt. Without effective antibiotics, modern living would still be at the mercy of simple bacteria.

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