"We now know the rate of occurrence of habitable planets around the most common stars in our galaxy, " said Prof Charbonneau.

BBC: Exoplanets near red dwarfs suggest another Earth nearer

The study found that the occurrence of difficult-to-treat infections in U.S. hospitals mirrored the rate of antibiotic prescribing in communities served by those hospitals, generally rising during flu season and subsiding in the spring and summer months.

FORBES: Private Physicians Drive Up Antibiotic Resistance, Helped Along By Patients

"Operations Director Carlos Murrieta pointed out that we have reduced the occurrence of accidents in recent years, " Pemex said on its Twitter page, adding that its accident rate was below international standards for similar companies.

WSJ: Deadly Blast Hits Mexico Oil Giant