Taking Action Against PVL-producing Strains Of Staphylococcus Aureus

Some strains of Staphylococcus aureus produce a potent toxin called Panton-Valentine leukocidin (PVL). PVL-Staphylococcus aureus (PVL-SA) usually causes skin and soft tissue infections, including boils and abcesses. More rarely it can cause serious diseases such as necrotising haemorrhagic pneumonia, which has been associated with a high mortality rate.

"Although several other countries have encountered widespread problems with PVL-related disease, infections caused by PVL S. aureus (including PVL MRSA) remain uncommon in the UK. Nonetheless we need to keep the situation under constant review," says Dr Angela Kearns from the Health Protection Agency. Tests carried out at the Health Protection Agency's Staphylococcus Reference Laboratory show that around 2% of all Staphylococcus aureus strains produce the PVL toxin.

"The HPA, working with other healthcare professionals, is in the process of updating guidance on PVL Staphylococcus aureus infection in the UK," says Dr Kearns. "This will provide healthcare professionals with advice to assist the recognition, investigation and management of PVL-SA cases."

To date, most strains of S. aureus that produce the PVL toxin in the UK have been sensitive to a range of antibiotics, including methicillin. These strains are called methicillin sensitive S. aureus (MSSA). In North America, strains of PVL Staphylococcus aureus, most notably the USA300 clone, have been spreading in the community and are resistant to methicillin. USA300 has become endemic in some US hospitals. In contrast, this strain has rarely been seen in England and Wales: 40 cases were identified during a two year study carried out in 2004/5 and most occurred in the community.

Since 2003, the HPA has actively been encouraging the referral of samples from cases of suspected PVL-related disease. Following these initiatives, 224 PVL-SA infections were identified in England and Wales in 2005; 117 (52%) of these were PVL-MRSA (so-called community-associated MRSA). In 2006, 496 PVL-SA were identified, 159 (32%) of which were PVL-MRSA. These figures show a small (0.4-fold) increase in the number of PVL-MRSA occurring nationally between 2005 and 2006.

"The risk to the UK general public of becoming infected with PVL-S. aureus is small but we must not be complacent," says Dr Kearns. "The Agency is actively working alongside healthcare colleagues to raise awareness of PVL S. aureus, as well as ensuring appropriate research continues to monitor trends in infection."

"These PVL strains shouldn't be confused with the hospital strains of MRSA that do not produce the PVL toxin and are more commonly associated with causing wound infections and blood-poisoning in elderly hospitalised patients," says Dr Kearns.

"Some of these infections are unavoidable, but we can help to minimise their impact by building on the wealth of knowledge we have from dealing with the hospital adapted strains of MRSA such as employing good hygiene measures which include proper cleansing and disinfection of cuts and minor wounds."