Nose Snot Antibiotic

Usually we look for antibiotics in exotic places such as Antarctica, aiming to find new drugs that no human pathogen has ever seen. But what if an antibiotic could be hiding in plain sight–or nearer yet, up your nose?

That’s what Alexander Zipperer and colleagues found, at the University of Tübingen. They focused on a pathogen Staphylococcus aureus, cause of serious skin infections including drug-resistant varieties such as methicillin-resistant Staph (MRSA). But S. aureus  has a surprising ability to hang out up the nose of healthy, unsuspecting carriers–that’s about one in three of us. Look to your right, then your left: One of you three’s got it.

So what keeps some of us healthy, despite this pathogen? The German researchers proposed there might exist some other nose-loving bacterium, part of our nasal snot microbiome–some bacterium that defends us from the bad ones. To find this white-knight defender, the researchers screened a collection of previously isolated nasal bacteria, cultured on a synthetic nasal medium (i.e. standardized snot). They tested individual isolates by dropping each culture upon a lawn of the tester strain Staph aureus. One isolate Staphylococcus lugdunensis showed a clear halo, a region where the tester Staph failed to grow.

The new S. lugdunensis was shown to produce a novel antibiotic, which they named lugdunin. Lugdunin (above) is a nonribosomal peptide; like vancomycin, the antibiotic is formed by a factory-modular enzyme that generates peptide bonds. Unlike ribosomal proteins, however, the nonribosomal peptide can contain all kinds of amino acids, beyond the canonical twenty. Lugdunin actually includes a thiazolidine, a unique five-membered ring including a sulfur atom.

So we may have a new antibiotic; or even a new probiotic, in the form of S. lugdunensis to inoculate our noses.