The nasty superbug MRSA has been linked to life-threatening conditions such as body-wide inflammation and organ failure, and now the NFL reports that New York Giants player Daniel Fells may lose his foot due to complications from an MRSA infection.

Fells was taken to the emergency room with a high fever a week after getting a cortisone shot to relieve pain from toe and ankle injuries. Doctors found that his ankle was infected with a bacterium called methicillin-resistant Staphylococcus aureus, or MRSA, and they fear that the infection might have spread to Fells' bone, which could make an amputation necessary, according to the NFL.

Doctors say that people with MRSA infections seldom need to have a limb amputated.

It's "very unusual for someone without a pre-existing condition to lose their foot from MRSA," said Dr. Bo Shopsin, an assistant professor of microbiology at New York University School of Medicine.

More commonly, infection-related amputations occur in people with severe diabetes or peripheral vascular disease, Shopsin told Live Science. For otherwise healthy people, it's rare, he said.

The Centers for Disease Control and Prevention reported that, in 2012, there were more than 75,000 cases of life-threatening MRSA infections in the United States, including nearly 60,000 that were acquired in health care settings, such as hospitals.

There have been cases in which injections, such as the cortisone injection Fells received, have led to these types of infections, Shopsin said. He estimated that he sees five to 10 people a year who acquired a staph infection from an injection, he said.

Early signs of an MRSA infection may include redness and swelling at the site of the injection and sometimes pus leaking out, Shopsin said.

At this point, MRSA infections can often be treated with powerful antibiotics. However, the longer an infection persists without treatment, the more severe it becomes.

Moreover, certain medications may mask the signs of infection by reducing inflammation. A cortisone injection could possibly mask the signs, Shopsin said.

MRSA can spread very quickly, Shopsin said. The bacteria replicate about every 20 minutes, so in a few hours, a patient can have massive quantities of the bacteria, he said.

Some strains of MRSA can cause a condition called necrotizing fasciitis — an infection of the tissue that lines the muscles, nerves and blood vessels throughout the body, Shopsin said. This "flesh-eating bacteria" infection, as it is sometimes called, can also make an amputation necessary, Shopsin said.

Another potential reason for amputation arises if the bacteria get into the bones.

Shopsin noted that when this occurs, it can be very difficult to treat.

Bone infections are a "major problem" because antibiotics can't reach them very well, and if they do get in, the antibiotics are less effective, Shopsin said.

Doctors can try treating bone infections by giving a patient antibiotics intravenously for a longer period of time, generally about six weeks, he said.

But the best way to treat a bone infection generally ends up being the removal of the bone, and in some cases, that means amputation, he said.

The NFL noted that the Giants' locker room was being "scrubbed and sanitized."

In general, following normal, good-hygiene practices prevents the spread of MRSA, Shopsin said. That means washing your hands well and making sure not to share items that frequently come into contact with people's skin, such as towels, he said.

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