Drug-resistant germ spreading outside US hospitals

8.25am

WASHINGTON - A drug-resistant "superbug" found in hospitals has a close cousin that is affecting athletes, prisoners and small children in growing numbers across the United States, disease experts said on Wednesday.

Methicillin-resistant Staphylococcus aureus or MRSA can become fatal if not treated with the right antibiotics, said Dr. Daniel Jernigan of the US Centres for Disease Control and Prevention.

"MRSA is showing up in places it had never been seen before -- as a predominant cause of skin disease among children in some regions of the country, as clusters of abscesses among sports participants, as the most common cause of skin infections among inmates in some jails and among military recruits and rarely, as a severe and sometimes fatal lung or bloodstream infection in previously healthy people," Jernigan told reporters.

Most commonly it takes the form of an abscess or boil, and doctors routinely try to treat it with penicillin-based antibiotics, Jernigan said. These will not work against MRSA.

In hospitals, MRSA resists almost everything but an intravenous antibiotic called vancomycin. But so-called community-acquired MRSA can be treated with a range of antibiotics including doxycycline and cotrimoxazole, sold under the brand name Bactrim.

However, 70 per cent of the time doctors use ineffective drugs to treat it, Jernigan said. And the community-acquired strain has some of its own nasty tricks.

"Unlike the hospital strains, the community strains were capable of producing a toxin called Panton-Valentine Leukocidin or PVL," he said.

"PVL is a necrotising cytotoxin, which means it can cause destruction of cells in the skin leading to pus formation but also can cause a serious and often fatal form of pneumonia."

This may be why MRSA infections cause large abscesses and are often first mistaken as spider bites, he said.

It is also easily passed around. "There is something about the community strain of MRSA that, when given the right circumstances and group characteristics, makes for very efficient transmission of the bacteria," Jernigan said.

He said the CDC is trying to persuade doctors to grow cultures from skin infections before treating patients, so they know which drugs to use. Improper use of antibiotics may be helping drive the evolution of drug-resistant bacteria, health experts say.

Jernigan said studies have shown MRSA makes up a significant number of all diagnosed staph infections, ranging from 9 per cent in Maryland, to 20 per cent in Georgia and 30 per cent in Hawaii.

The numbers are rising, Jernigan said. "We also found that rates of community-associated MRSA infections were disproportionately higher among children," he said.

In 2003, the Colorado Department of Public Health and Environment investigated an outbreak at a fencing club. Outbreaks were reported among high school and college football players and wrestlers in Pennsylvania, Indiana and California.

And between 1997 and 1999 four small children in North Dakota and Minnesota died from MRSA.

Jernigan said five factors were associated with outbreaks of the infection -- crowding, skin contact, abrasions or cuts in the skin, sharing contaminated equipment or towels and a lack of hygiene.

"From investigations of outbreaks at boot camp and in jails, it is clear that MRSA is being first brought into these settings by individuals that are carrying the bacteria in their nose without having any disease," Jernigan said.

"Once introduced, the bacteria can efficiently spread to others, and is then amplified in that setting."

- REUTERS