11 February 2013

Phenol-soluble modulin (PSM) Transport System Is Key To Developing Staph Infection Drug

Electron Microscope Image of Staphylococcus aureus
Credit: CDC
Scientists at the National Institutes of Health (NIH) are developing a new drug based on their studies on phenol-soluble modulins (PSMs) that can treat infections caused by Staphylococcus aureus.

Staphylococcus or simply staph, is a genus of Gram-positive bacteria. Gram-positive bacteria are bacteria that can be stained dark blue or violet by Gram staining. Staphylococcus appear round and form in clusters (see image).

There are about 40 species under the staphylococcus genus and most are harmless. But one strain of staph that may cause problems is the Staphylococcus aureus bacterium. It is commonly carried in the skin and the nasal passages (nose) by healthy people. Staphylococcus aureus is resistant to antibiotics and is a common cause of skin infections, respiratory disease, and food poisoning. S. aureus is a surface bacteria and can survive for months depending on the strain.

Infections occur when this bacteria enters the body through an open wound or when the skin is punctured or broken. One dangerous condition is MRSA or Methicillin-resistant Staphylococcus aureus (MRSA) infection. This is a strain that has become resistant to the medication used to commonly treat ordinary staph infections.

MRSA usually occur in hospitals and clinics. These are known as Health-care associated MRSA (HA-MRSA). Cases of HA-MRSA usually are associated with surgery, intravenous tubing, and other invasive procedures. Another type of MRSA that is becoming widespread especially in sports and athletic settings is the Community-associated MRSA infections (CA-MRSA). This is associated with skin contact, sharing of equipment/clothing, and other social interactions.

MRSA infections are hard to treat but mostly will eventually heal with proper care. But when left unattended, can result in health complications such as pneumonia, bone infections and even death.

Developing A New Type of Drug To Treat Staph Infections

National Institutes of Health (NIH) scientists have identified a promising lead for developing a new type of drug to treat infection caused by Staphylococcus aureus, a bacterium that frequently resists traditional antibiotics. The researchers discovered a system used by S. aureus to transport toxins that are thought to contribute to severe staph infections. These toxins—called phenol-soluble modulins (PSMs)—have gained much attention in recent years, but their multitude and diversity have hindered efforts to target them for drug development.

Video: Staph Infection

Expanding on work that first described S. aureus PSMs in 2007, scientists at the NIH's National Institute of Allergy and Infectious Diseases found that the transport system, which they call Pmt, is common to all S. aureus PSMs and critical for bacterial proliferation and disease development in a mouse model. Their experiments suggest that a drug interfering with Pmt's function could not only prevent production of the PSM toxins, but also directly lead to bacterial death.

Although their study focused on S. aureus, the scientists suspect that Pmt performs the same role in other staphylococci, such as S. epidermidis, the leading cause of hospital-associated infections involving indwelling medical devices such as catheters, pacemakers and prosthetics. They plan to continue their studies to improve the understanding of how PSMs function and to learn how to interfere with the Pmt transport system to block disease.


National Institutes of Health
National Institute of Allergy and Infectious Diseases
MRSA infection
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