Study Shows Antibiotic-resistant Bacteria Responsible For Increase In Muscle Inf

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Source: Infectious Diseases Society of America

Date: September 7, 2006

http://www.sciencedaily.com/releases/2006/09/060907104645.htm

Study Shows Antibiotic-resistant Bacteria Responsible For Increase

In Muscle Infections

Researchers in Houston, Texas have found two bacterial muscle

infections common in tropical countries becoming more frequent

occurrences along with the emergence of community-acquired

methicillin-resistant Staphylococcus aureus (CA-MRSA), according to

a study published in the Oct. 15 issue of Clinical Infectious

Diseases, now available online.

Staphylococcus aureus, or staph, is a common bacterium found on the

skin or in the nose of a quarter to a third of all people. Usually

harmless, staph can cause skin infections such as pimples and boils

and, less frequently, serious infections of surgical wounds or the

bloodstream, and pneumonia. For years, infections caused by

Staphylococcus aureus have been treated by inexpensive antibiotics

in the penicillin and cephalosporin family.

Some years ago, strains resistant to these drugs, called methicillin-

resistant Staphylococcus aureus (MRSA) appeared in hospitalized

patients. Recently, however, newer forms of MRSA began to strike

healthy people who have not been recently hospitalized or undergone

invasive medical procedures. These community-acquired strains appear

to be readily transmitted from person to person and can cause

serious skin and soft tissue infections as well as invasive

infections such as bone or joint infections or pneumonia. Failure by

physicians to suspect this kind of drug-resistant staph can lead to

treatment with the wrong antibiotic.

Pyomyositis is an acute bacterial infection of skeletal muscle that

produces an abscess within the muscle. Myositis is also a muscle

infection, but does not form an abscess. The study authors

investigated the 45 cases of pyomyositis or myositis in otherwise

healthy children who were hospitalized at Texas Children's Hospital

from 2000 through 2005. Sixteen of these cases were caused by CA-

MRSA and 10 by CA-MSSA (methicillin-susceptible Staphylococcus

aureus).

The number of cases increased year by year, from four cases in the

first year of the study to a high of 12 cases in the fifth year of

the study. The authors also discovered that a specific strain of

Staphylococcus aureus known as USA300 was associated with more

severe disease. Similarly, staph that carried a group of genes known

as PVL were also linked to a more severe illness.

" We're seeing an increasing number of muscle infections that is

clearly associated with an increase in MRSA, " said lead author Pia

Pannaraj, MD. " Physicians need to be aware that this is a

possibility and consider initial treatment with an antibiotic that

covers MRSA, particularly if they live in a region where methicillin

resistance is present. "