Plastics Lead Fight Against Antibiotic Resistance

MRSA bacteria
Scanning electron micrograph of methicillin-resistant Staphylococcus aureus bacteria (yellow, round items) killing and escaping from a human white cell.

Antibiotic resistant infections have cast a shadow on the future of medicine. The unnecessary overuse of antimicrobials and antibiotics in medicine and the agricultural industry has led to bacterial strains that resist even the strongest antibiotics. The horrible reality of a person contracting an infection through a minor cut and dying as a result has focused attention on finding alternative therapies to conventional antibiotics.

One such alternative is a polycarbonate (PC). Yi Yan Yang and other researchers at the A*STAR Institute of Bioengineering and Nanotechnology in Singapore have discovered an array of effective antimicrobial large polycarbonate molecules. These antimicrobial polymers were successful when tested using rat blood cells, illustrating a high potential for human use. The most significant property of these antimicrobial PCs is that by slightly modifying PC molecular structure, they can be adjusted to eliminate a particular microbe.

What Are Antibiotic Polymers?

Antibiotic PCs are composed of small monomers linked together to create long-chain polymers. The monomers are made up of two parts: The first is hydrophobic and can embed itself into the bacteria or fungal cell membrane, and the second part contains a group that is positively charged and is attracted to the negatively charged surface of a microbe. Tweaking the hydrophilic and hydrophobic balance attracts the polymer to the microorganism, causing membrane disruption and ultimately killing the cell.

Many clinically isolated multidrug-resistant bacteria and fungi have already proved no match for the polycarbonates used against them. Another benefit to using these polymers is their biodegradable property. Once a microbe has been eliminated, the polycarbonate will naturally break down and be eliminated by the body. This is a more appropriate option over current synthetic techniques that remain in the body, causing unnecessary and unwelcome side effects.

How Does Antibiotic Resistance Happen?

Conventional antibiotic drugs work by interrupting a critical function in the microbial cell. The microbes often mutate and change, eventually leading to a mutation that is resistant to the function of antibiotics therapy, creating an antibiotic-resistant strain. The video below illustrates how antibiotics work.

Due to the ability of the PC to enter the cell membrane, break it open and destroy the cell, the researchers don’t believe the microbes will be able to develop a resistance to them.

Future Studies

Yang said:

By carefully controlling the structure and the ratio of the two components, we can enhance dramatically the selectivity of the polymers toward a broad range of pathogenic microbes.

More experimentation is needed to determine the effects of further tweaking the polycarbonate monomers. A new study will also be performed using the PCs on methicillin-resistant Staphylococcus aureus (MRSA). MRSA is a bacterium that has become resistant to a wide range of antibiotics. The investigatory technique will involve injecting the PCs into infected mice.

Antibiotic-resistant microbes — “super-bacteria” or “super bugs” as they have been called — are one of the most troublesome problems in modern medicine. Even in the case of minor injury, exposure to and subsequent infection with these microorganisms can be deadly. New methods of fighting these mutant microbe strains are constantly under investigation. Any effective means of destorying them will increase the quality of health care and life for millions of people all over the world.

Image by NIAID.
Source: “Polymers That Can Be Fine-Tuned for Optimal Effect Could Help Fight Multidrug-Resistant Infections,” Phys.org, www.phys.org, July 02, 2014.
Source: “Polycarbonates to Tackle Multidrug Resistance,” A*Star Research, www.researcha-star.edu.sg, July 2, 2014.
Source: “Biodegradable Broad-Spectrum Antimicrobial Polycarbonates: Investigating the Role of Chemical Structure on Activity and Selectivity” by Willy Chin, et al., Macromolecules, November 15, 2013, DOI: 10.1021/ma4019685.