http://www.technologyreview.com/article/540181/die-bacteria/

Now researchers at MIT, the Broad Institute at MIT and Harvard, and Harvard University have engineered particles known as phagemids, which can produce toxins that are deadly to targeted bacteria.
Bacteriophages—viruses that infect and kill bacteria—have been used for many years to treat infection in the former Soviet Union. Unlike traditional broad-spectrum antibiotics, these viruses target specific bacteria without harming the body’s normal microflora.

Their novel method for growing bacteria has yielded 25 new antibiotics, with one deemed "very promising".
The last new class of antibiotics to make it to clinic was discovered nearly three decades ago.
The study, in the journal Nature, has been described as a "game-changer" and experts believe the antibiotic haul is just the "tip of the iceberg".
The heyday of antibiotic discovery was in the 1950s and 1960s, but nothing found since 1987 has made it into doctors' hands.
Since then microbes have become incredibly resistant. Extensively drug-resistant tuberculosis ignores nearly everything medicine can throw at it.

Antibiotic resistance is spreading faster than the introduction of new compounds into clinical practice, causing a public health crisis. Most antibiotics were produced by screening soil microorganisms, but this limited resource of cultivable bacteria was overmined by the 1960s. Synthetic approaches to produce antibiotics have been unable to replace this platform. Uncultured bacteria make up approximately 99% of all species in external environments, and are an untapped source of new antibiotics. We developed several methods to grow uncultured organisms by cultivation in situ or by using specific growth factors. Here we report a new antibiotic that we term teixobactin, discovered in a screen of uncultured bacteria. Teixobactin inhibits cell wall synthesis by binding to a highly conserved motif of lipid II (precursor of peptidoglycan) and lipid III (precursor of cell wall teichoic acid). We did not obtain any mutants of Staphylococcus aureus or Mycobacterium tuberculosis resistant to teixobactin. The properties of this compound suggest a path towards developing antibiotics that are likely to avoid development of resistance.