I'm a clinical microbiologist working in a teaching hospital in India. We've been seeing multi-drug resistant strains of hospital bugs (Gram negative) for quite some time now.

In fact, more than 60% of the Gram negative isolates in our hospital (in-patients) appear to be producing an enzyme called extended spectrum beta lactamases (ESBL). These ESBL-strains are often resistant to other classes of antibiotics as well, narrowing therapeutic options. In a subset of cases, these bugs turn up as resistant to almost all the antibiotics we test.

But, I am yet to come across a case where the isolate was resistant to colistin and polymyxin B. No clinician would even think of using these drugs if other options are available. But, if, as the article reports, these organisms turn out to be resistant to even these last-resort drug... we can safely assume that we are in deep shit.

Like the parent poster says, Escherichia coli is part of our gut flora... but that does not mean that it does not cause diseases in humans.

It is the COMMONEST cause of urinary tract infections. It can cause various forms of diarrhoeal diseases, including traveler's diarrhoea and haemorrhagic diarrhoea. It easily acquires resistance to multiple antibiotics in the hospital environment... and is a very common agent in hospital acquired infections. Treating an infection caused by multi-drug resistant E. coli is a HUGE pain in the butt (I speak from experience).