Scott Harper first thought he had an ingrown hair on his left arm. There was a hot-pink bump, almost like a pimple, that seemed hot to the touch. And it really hurt.

By the time he got home from work the next night, it had grown to the size of a quarter and was deep red. The next day his entire arm was swelling, the area was livid, nearly purple, and the pain was unbearable. He headed for the emergency room.

ER staffers took one look and checked him in. It was clearly a staph infection. And within a short time they learned it was something far worse: methicillin-resistant Staphylococcus Aureus (MRSA).

In other words, one of the bacteria health officials have been warning about for several years: bacteria that have become resistant to an entire class of antibiotics.

Harper's case is one of a new and growing trend: MRSA once originated primarily in hospitals and nursing homes, where antibiotics were commonly used. Now they're showing up in the community and sending people to hospitals, the infection already onboard.

"What's happened beginning about four to five years ago is a change in some types of resistant organisms shifting from being primarily located in hospitalized patients to becoming more of a problem in communities. One that has done that successfully is MRSA," said Dr. Matthew Samore, associate professor in the Division of Clinical Epidemiology at the University of Utah.

"This is also a ubiquitous organism that lives on skin, in the nose, all around us. It causes problems when it gets into the wrong place. What makes MRSA particularly challenging is that it is something that is resistant to almost all drugs."

What was considered the "big gun" for MRSA — vancomycin — has in some cases been rendered worthless because some of the bacteria are now becoming resistant to it as well, said Dr. Patrick Luedtke, deputy state epidemiologist in the Utah Department of Health. So MRSA is becoming VRSA, which is even harder to treat.

Staph infections are common. Staphylococcus bacteria are commonly carried on the skin or in the nose of healthy people, and only occasionally do they cause an infection. In fact, as many as 30 percent of the population have staph bacteria in the nose at any given time. But staph bacteria are among the most common causes of skin infections in the United States, according to the Centers for Disease Control and Prevention.

Most are mild, like pimples and boils, and don't require antibiotic treatment. But they can also be serious, such as surgical wound infections or pneumonia. A type of antibiotic related to penicillin has been used for more than 50 years to treat such serious infections. MRSA are the resistant bacteria that now don't respond to those antibiotics.