Drug-resistant bug kills young and healthy in U.S.

By Maggie Fox, Health and Science Editor

WASHINGTON (Reuters) - A germ that usually causes pimples or skin rashes caused fatal pneumonia in at least 24 otherwise young and healthy people during the 2006-2007 flu season and doctors need to watch for it, U.S. researchers said on Tuesday.

Many of the cases were caused by a drug-resistant form called methicillin-resistant Staphylococcus aureus or MRSA, said the team led by the U.S. Centers for Disease Control and Prevention.

Some of the patients died within four days and many were not initially treated for MRSA, which suggests their doctors had no idea what they had at first, said the CDC's Dr. Alexander Kallen, who led the study.

"It's obviously very concerning," Kallen said in a telephone interview. "This is a disease that can strike otherwise very healthy people -- adults and children. Also this is a disease that follows influenza."

That has implications for planning for the flu season and also preparing for a possible flu pandemic, said Kallen.

His team checked reports of community-acquired pneumonia caused by Staph aureus between November 1, 2006, and April 30, 2007. "Overall, 51 cases were reported from 19 states," they wrote in the Annals of Emergency Medicine.

"More than three-quarters (79 percent) of the staph-caused pneumonia patients were infected with MRSA," Kallen said.

On average the patients were 16 years old. One-third had confirmed influenza but 40 percent were perfectly healthy.

They said 24 patients died, an average of four days after being diagnosed with pneumonia. Patients who had flu were about twice as likely to die from the staph-caused pneumonia.

"The key message to realize is that during the winter season, especially when influenza is circulating, physicians need to be thinking about this as a cause."

Staph aureus is common -- about 30 percent of people are colonized with it at any given time, meaning they have the bacteria living on their skin or in their noses but are not ill.

"You shake hands with someone and you get MRSA and MRSA colonizes you," Kallen said.

It can get into the lungs sometimes and cause disease.

Some studies have shown that when people are infected with flu, the virus can help shut down natural processes for keeping the lungs clear and allow the bacteria to grow there.

Kallen said MRSA-caused pneumonia may not be getting more common, but doctors are now keeping an eye out for it and reporting it. "This probably overrepresents the true picture of MRSA," Kallen said.