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In a steady march, disease-causing microbes have evolved ways to evade the bulwark of medications used to treat bacterial infections. For a variety of those illnesses, only colistin continued to work every time. Now this last line of defense had been breached as well. A second U.S. case of E. coli with the mcr-1 resistance gene was reported this week in the journal Antimicrobial Agents and Chemotherapy. (Healy, 7/11)

And then there’s teixobactin, a still-experimental drug that may herald a new era of antibiotic discovery. A team of researchers at Northeastern University’s Antimicrobial Discovery Center reported last year in the journal Nature that they had discovered a compound in soil unlike any found before. Teixobactin was highly effective in killing such common bacterial troublemakers as Clostridium difficile, Mycobacterium tuberculosis and Staphylococcus aureus, wrote a team led by Kim Lewis, the center’s director. A Nature editorial dubbed it “an irresistible newcomer.” (Healy, 7/11)

It's been nearly 30 years since scientists have found a new class of antibiotics. But U.S. lawmakers tried to give the drug industry a boost in 2012. That year, they passed the Food and Drug Administration Safety and Innovation Act. It included provisions — collectively known as Generating Antibiotic Incentives Now, or GAIN — aimed at streamlining the government approval process for new antibiotics. It also boosted financial paybacks to drug companies that develop them. The law has spurred the introduction of several new medicines. But none so far represents a new class of antibiotic or treats a drug-resistant strain for which effective medicine does not already exist. (Healy, 7/11)

How quickly can antibiotic resistance spread? Consider the case of a Swedish man who traveled to India in 2009. While in New Delhi, the man became infected by a strain of Klebsiella bacteria bearing a gene that made it impervious to the antibiotic carbapenem. Microbiologists quickly found the gene in bacterial samples from Mumbai as well. In the span of just two years, it also turned up in Croatia, Pakistan, the United Kingdom, Canada, Japan and China. (Healy, 7/11)

Farm animals are a key player in the emergence of antibiotic resistance. Around the world, livestock producers feed antibiotics to cattle, pigs, chickens and other animals in a bid to prevent diseases and boost their growth. In the United States, for instance, some 30 million pounds of antibiotics are used on the farm. That’s 80% of all the antibiotics used in the U.S. each year, according to the Pew Charitable Trusts. Experts believe this practice has hastened the emergence of antibiotic-resistant diseases. (Healy, 7/11)