As bacteria become resistant to more and more of our antibiotics, we may be running out of weapons. Ceftobiprole offers new hope in our microbial war. Eric Libby reports.

Throughout the history of antibiotics, there has been a steady arms race between humans and bacteria. We design a drug that kills them, they develop resistance to it, and we look for another drug. Increasingly, we  encounter strains of bacteria like MRSA or multi-drug resistant Staphylococcus aureus that are resistant to multiple antibiotics.

"Mortality by MRSA infections is surprisingly high," says Alexander Tomasz of Rockefeller University.  "Also this bacteria that we are formerly called the hospital bug.  You [used to acquire] them when you went to a hospital, now these same bugs show up in the community."

Tomasz and colleagues found that a new antibiotic called Ceftobiprole annihilated colonies of MRSA. Like penicillin ? one of the first and still one of the most widely used antibiotic agents ? Ceftobiprole binds enzymes crucial to making bacterial cell walls, ultimately killing the bacteria.

After widespread use of penicillin, the Staph bacteria developed enzymes less likely to attach penicillin, becoming resistant to the drug. Ceftobiprole manages to elude the bacteria's resistance and bind the enzymes once again.

Moreover, Tomasz says that Ceftobiprole proved effective even against bacteria that were already highly resistant to powerful antibiotics.

Within bacteria populations there are small subpopulations, say 10,000 out of ten billion, of especially drug resistant bacteria. This subpopulation may be a hotbed for new resistance, sharing their tricks with other bacteria. Tomasz deliberately tested Ceftobiprole on this subpopulation and found "to [his] delight they were wiped out. So that particular resource which the bugs already seem to have put into reserve, they don't succeed."

Although Tomasz is excited about this new potential weapon against MRSA, he cautions that bacteria are true survivors and capable of finding a way around any drug, even Ceftobiprole. So the war against Staphylococcus aureus continues.

The research will appear in the August 2008 issue of the journal Antimicrobial Agents and Chemotherapy and is available online now.