I was listening to NPR Science Friday on podcast a few nights ago and caught an interesting segment detailing a recent discovery regarding bacteria found in soil.  It has been demonstrated (for example, by the discovery of the nylon bug) that bacteria in the presence of an abundance of one substance or another may evolve to be able to metabolize that substance... even if the substance is synthetic.  It's also been shown that bacteria in the constant presence of antibiotics will evolve immunity.

These newly discovered soil bacteria have done both.  That is, not are they only immune to a disturbingly long list of known antibiotics, they have evolved to the point where they can actually eat antibiotics.  The Royal Society of Chemisty has an article on this recent discovery:

[...] The soil samples were taken from many different places [in the USA] including public parks and farms, pristine forest, and land treated with wastewater.

'The increase of multiple-antibiotic resistance in human pathogens is continuingly weakening our ability to fight infectious disease, and any accessible reservoir of resistance mechanisms that could transfer to pathogens could exacerbate the problem,' say Dantas and Sommer.  

So far, the researchers haven't found any known human pathogens among their antibiotic-consuming organisms, but they say that some are closely related species. This might make it rather easy for pathogens to acquire antibiotic-resistance and antibiotic-metabolising genes from innocuous bacteria. [...]

Scary stuff!  But rather unsurprising since antibiotics get into the environment every day through their continued use.

The segment on the antibiotic-munching bacteria was followed by another segment on an alternative form of antibacterial treatment called phage therapy.  Phage therapy, instead of using chemical substances to combat bacteria, uses viruses, specifically bacteriophages--viruses that only infect bacteria.  This sort of therapy was predicted shortly after the discovery of bacteriophages in 1917.  Once antibiotics were discovered (in 1941) phage therapy wasn't pursued further in the west, but continued to be studied in Russia.

The advantage of phage therapy is that the anti-bacterial agent is also a living organism, so as bacteria evolve to become immune to it, the phage species also evolves to continue to prey on the bacteria.  Antibiotics, being chemical compounds, do not evolve, hence eventually bacterial evolution will defeat an antibiotic unless you can rapidly deplete the bacterial population to the point where your own immune system can fight off the infection successfully.  As bacteria with antibiotic resistance can be found in the environment, and people have been infected with resistant strains, there is apparently renewed interest in phage therapy.

No human phage treatments are presently approved in the USA, though the use of phages to prevent bacteria from growing in food have been approved here.  Phage therapy on humans is used in some states of the former USSR, especially Georgia.  In the NPR podcast linked above the scientists interviewed spoke of a patient with a resistant bone infection that was successfully treated using bacteriophages after being told here in the USA that amputation was his only recourse.  Interesting!