Drug-resistant bacteria increasingly causing infections in healthy people

An emerging form of so-called "flesh-eating bacteria" is caused by a strain that is resistant to standard first-line antibiotics. The same type of bacteria, methicillin-resistant Staphylococcus aureus (MRSA) is causing record numbers of less-serious skin infections in children and also is emerging as a cause of pneumonia, which can be deadly.

• Physicians are seeing more and more infections caused by drug-resistant bacteria, including skin boils, pneumonia and even so-called "flesh-eating bacteria."
• Until recently, infections caused by methicillin-resistant Staphylococcus aureus (MRSA) were unusual in healthy people outside of the hospital.
• Infections caused by MRSA must be treated with different antibiotics.
• Infectious diseases experts are concerned the bacteria will soon become resistant to those antibiotics as well, and few new drugs are in the development pipeline.

Numerous studies on the rise in infections caused by MRSA among healthy people outside of the hospital - nearly unheard of a few years ago - are being presented at the 42nd Annual Meeting of the Infectious Diseases Society of America (IDSA).

"The rate of MRSA infections has risen to epidemic proportions in some places, and the curve isn't flattening out yet," said Kevin Purcell, MD, PharmD, principal investigator of a study on MRSA-caused skin infections at Driscoll Children's Hospital in Corpus Christi, Texas. "Staphylococcus aureus is a bad bug to begin with and this resistant form also is more potent, making it easier for people to become infected."

MRSA is a concern because antibiotics prescribed by physicians only a few years ago typically no longer work. Over time, bacteria can mutate and become resistant to specific antibiotics. Effective antibiotics are available to treat MRSA, but physicians are concerned that the bacteria will eventually become resistant to those as well. Drug-resistant infections have long been a problem in hospitals and among the elderly and chronically ill, but in recent years physicians are seeing these infections more and more in healthy people.

"These reports highlight our concern over the crisis of antibiotic resistance, a problem that is magnified because there simply aren't enough new drugs in the pharmaceutical pipeline to keep pace with the evolution of drug-resistant bacteria, the so-called 'superbugs,' " said Joseph R. Dalovisio, MD, IDSA president. "This crisis has the potential to touch us all because drug-resistant infections can strike anyone - young or old, healthy or chronically ill."

MRSA and "Flesh-Eating Bacteria"

One study being presented at the meeting documents 14 cases of necrotizing fasciitis (known colloquially as the "flesh-eating bacteria") in Los Angeles caused by MRSA, an uncommon cause of the illness. None of the patients died, but all had surgery to remove infected flesh, three needed reconstructive surgery (such as skin grafting) and 10 spent time in the intensive care unit, one for a month. Half originally were thought to have less-serious skin abscesses. Four patients initially were given antibiotics to which the bacteria were resistant, but all 14 patients were eventually successfully treated with the antibiotics vancomycin and/or clindamycin.

Necrotizing fasciitis infections can start in a small cut or trauma and spread throughout the body within hours or days if not treated with surgery and antibiotics. Most cases of necrotizing fasciitis are caused by a different type of bacteria called Group A streptococcus (the same type of bug that causes strep throat) and about a third are fatal.

"This is about as serious an infectious disease emergency as you can get," said Loren G. Miller, MD, MPH, principal investigator at the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center (LA BioMed) and assistant professor of the David Geffen School of Medicine at UCLA. "Thankfully no one died, but physicians need to be aware that if they see cases of necrotizing fasciitis, they should treat for this resistant bug (MRSA) in addition to the other known causes until they know the causative bacterial. This is a major shift in treatment approach.

"We don't know how these people got the infection - there doesn't seem to be a common thread," said Dr. Miller, who also is a staff physician at Harbor-UCLA Medical Center, Torrance, Calif. "Four of the people had absolutely no other medical conditions or risk factors."

MRSA-Caused Skin Infections in Children

From New York to Texas, Maryland to Missouri, researchers are presenting reports at IDSA on the exponentially increasing incidence of MRSA-caused skin boils in non-hospitalized children.

The boils - called abscesses - typically are red and raised, and can be gumball to golf-ball sized. The abscesses can appear anywhere on the body, often on the backs, legs, buttocks and arms, and are filled with pus. Treatment involves draining the abscess, cleaning the wound and prescribing appropriate antibiotics.

Although the infections are rarely fatal, treating physicians must recognize that they may be caused by the MRSA, and treat them with stronger antibiotics.

One study at Driscoll Children's Hospital in Corpus Christi, Texas, reports the number of infections caused by MRSA shot up in five years, from 9 in 1999 to 459 in 2003; between 1990 and 1999, there were fewer than 10 cases each year. The infections were predominantly abscesses (94 percent), but a few were life-threatening infections such as pneumonia, endocarditis (heart infection) and toxic shock syndrome. Of the 928 children who got these infections between 1990 and 2003, nearly 9 in 10 were healthy, and had no risk factors that would predispose them to the infection. Of the 737 children who had the infections in 2002 and 2003, nearly half (49 percent) had to be admitted to the hospital for treatment with intravenous antibiotics. None of the children died.

"We're seeing more and more families whose members are passing the MRSA back and forth and in those cases everyone needs treatment to eradicate the bug from their bodies," said Dr. Purcell, a health care consultant to Driscoll Children's Hospital. MRSA bacteria usually live in the nose, are spread by touching the nose and then the skin, and can be treated with an antibiotic cream that is applied in the nostrils.

MRSA-Caused Pneumonia

While skin infections are rarely deadly, pneumonia can be. Although Staphylococcus aureus is one common cause of pneumonia in hospitalized people, the resistant form of staph is newly emerging as a cause of pneumonia in healthy people. A Centers for Disease Control and Prevention (CDC) study being presented at IDSA reports on 17 people in 9 states who got pneumonia caused by MRSA outside of the hospital during last year's flu season. Of the 17, 5 (29 percent) died, 16 (94 percent) were hospitalized for an average of 22 days and 12 (75 percent) were admitted to the intensive care unit. One of the people who died had diabetes, while the rest had no known illnesses or factors that would put them at risk for the infection.

"Most of these cases first had influenza virus infection and progressed to MRSA pneumonia," said principal investigator Jeffrey Hageman, MHS, epidemiologist for CDC. "With the flu season just around the corner, physicians need to be aware that in some cases the bug causing the pneumonia may be resistant to the antibiotics typically used, and may need to be treated with alternative drugs."

Co-authors of a paper on the topic of necrotizing fasciitis being presented at IDSA by Dr. Miller are Francoise Perdreau-Remington, Sheherbano Mehdi, Josh Perlroth, Tieu Phung, Gunter Rieg, Angela Tang and Brad Spellberg.

Jaime Fergie is a co-author of the study on MRSA in children being presented at IDSA by Dr. Purcell.

Co-authors of a study on pneumonia caused by MRSA being presented by Hageman at IDSA are John Francis, Timothy Uyeki, Stephen Barenkamp, Meg Doherty, Uri A. Lopatin, David Lonsway, Linda McDougal, Daniel Jernigan, George Killgore and L.C. McDonald.

IDSA is an organization of physicians, scientists and other health care professionals dedicated to promoting human health through excellence in infectious diseases research, education, prevention and patient care. Major programs of IDSA include publication of two journals, The Journal of Infectious Diseases and Clinical Infectious Diseases, an Annual Meeting, awards and fellowships, public policy and advocacy, practice guidelines and other membership services. The Society, which has 7,500 members, was founded in 1963 and is headquartered in Alexandria, Va.

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