New compound found effective against resistant microbes

London, May 28 (IANS) An active compound, plectasin, from fungi and lower animals may well be suitable as an effective weapon against dangerous bacteria.

Plectasin is a small protein molecule that can even destroy highly resistant bacteria.

Researchers at the University of Bonn, Utrecht, Aalborg and of Danish company Novozymes AS have shed light on how the substance does this. The authors see plectasin as a promising lead compound for new antibiotics.

More and more bacteria are becoming resistant to normal antibiotics. This is especially true for the methicillin-resistant Staphylococcus aureus (MRSA).

Most of the pharmaceutical weapons are now useless against these MRSA strains. According to estimates, as many as every second patient in the US treated by intensive-care medicine comes down with an MRSA infection.

Plectasin could shift the balance of power back in the doctors’ favour. But how exactly does the little protein molecule do that?

University of Bonn (UB) researchers in Tanja Schneider and Hans-Georg Sahl’s team have answered these questions together with Danish and Dutch colleagues.

Plectasin disrupts the forming of the cell wall in bacteria so that the pathogens can no longer divide.

In this process, plectasin behaves like a thief which steals the stones off a mason.

‘It binds to a cell-wall building block called lipid II and thus prevents it from being incorporated,’ Sahl, a professor, explains.

‘However, a bacteria cannot live without a cell wall,’ he said.

It comes as no surprise that the most famous antibiotic penicillin also inhibits cell-wall synthesis.

Yet, plectasin is more similar in its mode of action to another widely used drug, vancomycin.

Vancomycin had been the drug of choice in combating MRSA strains since the 1980s. Meanwhile, though, there are more and more bacteria that are also resistant to vancomycin.

‘However, these strains are still susceptible to plectasin,’ Schneider emphasises. Nevertheless, there is no permanent solution to the resistance problem even with a new antibiotic.

‘It is always just a question of time until the pathogens mutate and become insensitive,’ she says. ‘It’s a never ending arms race.’

Plectasin belongs to the class of defensins. These defence molecules are widespread among fungi, animals and also plants, said a University of Bonn release.

Humans, for example, produce defensins on their skin and in this way nip infections in the bud.

‘Defensins not only kill pathogens but also alert the immune system,’ Hans-Henrik Kristensen from Novozymes AS explains. ‘So the pharmaceutical industry is setting its hopes on them.’

These results were published in the Friday edition of Science.