New research may give penicillin teeth even against 'superbugs'

17 April 2014

A new approach may restore the once wonder-drug penicillin's effectiveness even against 'superbugs', by pairing the drug with a protective polymer, researchers said on Wednesday.

''Penicillin, one of the scientific marvels of the 20th century, is currently losing a lot of battles it once won against bacterial infections,'' scientists at the University of South Carolina said.

Bacteria have been chipping away at the power of the penicillin family of drugs since their first wide-scale use as antibiotics in the 1940s. Now, the new approach to restoring its combat effectiveness can help even against so-called superbugs.

A cyclic four-membered amide ring termed a beta-lactam is a common structural element of the penicillins, their synthetic and semi-synthetic derivatives.

Physicians heavily use the many versions of beta-lactam antibiotics to fight bacterial infections, and many have been retired because they're no longer effective against the defences bacteria have evolved in response.

One of the most effective bacterial defences is an enzyme called beta-lactamase, which chews up the beta-lactam structure, researchers said.

Some bacteria, such as MRSA, have developed the ability to biosynthesise and release beta-lactamase when needed. The new approach led by Carolina University's Chuanbing Tang pairs the drug with a protective polymer developed in his chemistry laboratory.

In lab tests, graduate student Jiuyang Zhang prepared a cobaltocenium metallopolymer that greatly slowed the destructiveness of beta-lactamase on a model beta-lactam molecule (nitrocefin).

The interdisciplinary team also showed that the antimicrobial effectiveness of the four beta-lactams studied in detail was enhanced by the polymer. The enhancement was modest against two strains, but very pronounced with the hospital-associated strain of MRSA (HA-MRSA).

The metallopolymer by itself even demonstrated antimicrobial properties, lysing bacterial cells while leaving human red blood cells unaffected. By a variety of measures, the polymer was found to be nontoxic to human cells in laboratory tests.

The research has been published in the Journal of the American Chemical Society.

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