The Food and Drug Administration on Friday approved a new antibiotic from Cubist Pharmaceuticals to treat common skin infections often acquired in the hospital.

Regulators cleared the company's Sivextro as a pill and as an intravenous solution for adults with skin infections caused by bacteria that are often resistant to older antibiotics.

It's the second FDA approval in less than a month for a new antibiotic to treat such infections. In late May, the FDA approved a similar drug from Durata Therapeutics Inc.

Antibiotics like penicillin and streptomycin first became widely available in the 1940s, and today dozens are still used to kill or suppress the bacteria behind illnesses ranging from strep throat to urinary-tract infections. The drugs are considered one of the greatest advances in the history of medicine, and have saved countless lives.

But in recent decades some common bacteria have grown resistant to antibiotics that were once highly effective. Experts say overuse and misuse of the drugs by physicians has contributed to the rise of these so-called superbugs.

The FDA gave Sivextro an expedited review under a 2012 law designed to encourage drugmakers to invest in researching and development of new antibiotics. Under the measure, Cubist will receive an additional five years of exclusive marketing rights to the drug.

Sivextro is designed to be taken over six days as a daily intravenous infusion or as a tablet. Cubist says the oral form of the drug gives patients the option of completing therapy at home, which could cut down on hospital-stay costs.

The drug works against a variety of common bacteria, including Staphylococcus aureus, Streptococcus species and Enterococcus faecalis.

The Centers for Disease Control and Prevention estimated last year that the staph infection methicillin-resistant Staphylococcus aureus, or MRSA, kills about 11,000 people annually.

The most common side effects seen in company studies were nausea, headache, diarrhea, vomiting and dizziness.

Lexington, Massachusetts-based Cubist gets over 80 percent of its revenue from a single product: the antibiotic Cubicin, which is used to treat infections of the skin and blood. Last fall the company paid $1.24 billion to acquire rival drugmakers Trius Therapeutics and Optimer Pharmaceuticals Inc., both developers of antibiotics.

Shares of Cubist Pharmaceuticals Inc. rose $1.26, or 1.7 percent, to $73.50 in afterhours trading Friday.