Antibody-Antibiotic Superdrug Triumphs over MRSA Superbug in Mice

By latching onto bacteria and detonating at just the right moment, a new drug could help take out the leading cause of bacterial infections in humans worldwide.

The drug, a deadly combo of an antibody glued to an antibiotic, specifically seeks and destroys Staphylococcus aureus—even the difficult-to-kill, drug-resistant variety, methicillin-resistant staph (MRSA). In mice infected with MRSA, the dynamic duo fought off the infection better than the standard antibiotic treatment of vancomycin, researchers report in Nature. If the findings hold true in humans, the new superdrug could vastly improve the success rate of MRSA infection treatments, which currently fail about 50 percent of the time.

…But, for now, there are no guarantees that the superdrug will be that effective in human patients. Researchers point out that the human immune system may produce competing antibodies that bind to staph, possibly elbowing out the superdrug.

Source: Antibody-antibiotic superdrug triumphs over MRSA superbug in mice

The article (and the paper its based on) overstates things and make this much more alarmist than it should be.  MRSA infection treatments do not “currently fail about 50 percent of the time.” MOST MRSA infections are readily treatable and cureable. There are a few difficult to treat exceptions that are much more difficult to treat (endocarditis, osteomyelitis, necrotizing soft tissue infections) that have higher failure rates.

As for the actual bacteria, methicillin resistant staphylococcus aureus is absolutely resistant to an entire class of antibiotics (beta-lactam antibiotics) because the bacteria has an altered protein that no longer binds the active site of these antibiotics. So we have to use different classes of antibiotics for treatment (such as vancomycin, linezolid, daptomycin). It does also happen to have a way to hide inside phagocytic cell thereby avoiding the immune system and our antibiotics. This has been known for a long time.

This is an interesting proof of concept study. They definitely need to do some more comparisons. They’re using a class of medications as the “antibody-linked antibiotic”, rifamycins, that is well known to penetrate spaces like lysosomes and biofilms. They compared it against antibiotics that have a much harder time doing this (glycopeptides ect). So a better comparison would be rifampin vs this targeted rifalogue. It could be a very elegant way of targeting deep-seated difficult to treat infections however.