What is PVL Staphylococcus aureus?

Panton-Valentine Leukocidin (PVL) is a toxic substance produced by some strains of Staphylococcus aureus which is associated with an increased ability to cause disease. The incidence of PVL-related disease in the UK is low at present but it is important healthcare professionals and the public are aware of the infections it can cause and the precautions which should be taken.

PVL can be produced by both meticillin sensitive and meticillin resistant strains of S. aureus. Most of the PVL-positive S. aureus strains identified in the UK are sensitive to many antibiotics.

How common is PVL S. aureus?

The PVL toxin is carried by less than 2% of S. aureus and can be carried by both MRSA (meticillin resistant Staphylococcus aureus) and MSSA (meticillin sensitive Staphylococcus aureus ).

During 2005 and 2006, a total of 720 cases of PVL-SA were identified from isolates referred to the HPA Staphylococcus Reference Unit for testing and characterization. Of these, 224 were in 2005 and 496 in 2006, representing a two-fold increase, possibly the result of increased awareness and reporting.  Provisional data for 2007 show 1361 PVL-SA were identified, representing a 2.7-fold increase over the 2006 figures. Of the 1361, 845 (62%) were PVL-MSSA and 516 (38%) were PVL-MRSA.

We are aware of isolated cases and clusters of disease, occurring predominantly in the community across the United Kingdom (UK). Microbiology laboratories across the UK are vigilant and have been requested to send any suspicious samples to the HPA for further analysis.

What are the symptoms?

Infections caused by PVL strains of S. aureus normally cause cellulitis (inflammation of layers under the skin) and pus-producing skin infections (eg abscesses, boils and carbuncles). They can, however, on very rare occasions, lead to more severe invasive infections, such as septic arthritis, bacteraemia (blood poisoning) or necrotising pneumonia (a severe, life-threatening form of pneumonia).

Why do people get PVL S. aureus infections?

Not all patients with PVL S. aureus will suffer an infection. When these occur they are usually associated with the presence of other risk factors such as overcrowding, skin abrasions resulting from close contact sports such as wrestling or rugby, or using contaminated articles such as sharing towels, razors, poor hand hygiene and damaged skin from other conditions such as eczema.

What should people do to protect themselves?

The risk to the general public of becoming infected with PVL S. aureus is small but it is always good practice to maintain appropriate hygiene measures which include proper cleansing and disinfection of cuts and minor wounds. Wounds should be covered with a bandage until healed and individuals should avoid contact with other peoples' bandages and lesions.

If the infection spreads or recurs go to your GP or Accident and Emergency for further investigation and/or treatment. Such spreading infection should not be ignored.

Other simple measures are regular bathing/showering, regular changing of linen and underwear, hand washing, avoiding sharing personal items (eg toothbrushes, face cloths, towels) and keeping wounds covered.

Chances of contracting all types of S. aureus infections are reduced by maintaining good hand hygiene and not sharing personal items. In shared facilities (for instance, in gyms) it is good practice to use liquid soap and disposable towels, to place a towel on the bench before sitting, and to ensure the facilities are cleaned frequently and that there is good ventilation to the locker room and showers.

Is this a new type of MRSA?

PVL-producing strains of MSSA have been seen in the UK before. In the 1950s and 1960s a particular type of PVL-MSSA was common in hospitals, but is not common currently. It is thought that PVL-positive MRSA have evolved from strains such as these. Unlike the PVL-negative MRSA found in hospitals in the UK , the small numbers of PVL cases reported have usually been in the community setting.

Can people die from it?

Infection with PVL-producing strains of S. aureus normally causes skin infection, but can occasionally cause more severe infections. The HPA is aware of seven deaths in England and Wales associated with PVL-positive MRSA over the last two years. Most of these were unrelated to hospital care.

 

Can PVL-MRSA and PVL-MSSA be treated?

Yes, both types of PVL producing S. aureus can be treated. It is important to diagnose infection early. Infections caused by many antibiotic-sensitive varieties of PVL- S. aureus are usually successfully treated with antibiotics such as some types of penicillin and erythromycin. PVL-MRSA are resistant to antibiotics of the meticillin-class (eg flucloxacillin) and occasionally other antibiotics such as erythromycin. Isolates seen in this country are usually susceptible to many other antibiotics such as tetracycline, ciprofloxacin, rifampicin, trimethoprim and fusidic acid. Effective treatment is therefore readily available.

What decontamination methods can be used on people, wards, clothing etc?

As with any kind of S. aureus, thorough hand washing and drying, or use of alcoholic hand rubs if hands are not visibly soiled, have been shown to be the most important measures in reducing cross-infection in both the community and the hospital.

The environment must be kept clean and dry. While in hospital, patients may have to be nursed in side-rooms or in a special ward and visitors may be asked to wear gloves and aprons. Before going home visitors may be advised to wash their hands or use an alcoholic hand rub even if hands are not visibly soiled.

 

What is PVL-positive MRSA?

MRSA (meticillin resistant Staphylococcus aureus ) refers to a common bacterium that has developed resistance to a range of antibiotics. PVL-positive MRSA therefore refers to a type of MRSA which produces the PVL toxin. These PVL-MRSA strains are also commonly referred to as 'Community-associated MRSA' (CA-MRSA).

Who can PVL-positive MRSA affect?

PVL-producing strains are more commonly contracted in the community and generally affect previously healthy young children and young adults – this contrasts with the so called 'hospital-associated MRSA' strains which do not usually produce PVL and are more commonly associated with wound infections and blood-poisoning in elderly or severely ill hospitalised patients.

At the moment PVL-MRSAs are not common in the UK hospital setting.

What infection control measures can be used to stop the spread of PVL-positive MRSA?

The infection control measures used to prevent the spread of PVL-positive MRSA are the same as for any type of MRSA infection. Standard infection control measures are effective and the most important first line of defence. In healthcare settings, measures include early diagnosis and treatment of cases, barrier nursing, and sometimes investigation of close contacts.

Is PVL-producing MRSA more dangerous than other strains seen in the UK and elsewhere?

While PVL-producing MRSA can cause serious infection, we have no evidence to suggest it is more dangerous than some other types of MRSA. Indeed, some previous and more recent data suggests that the PVL gene may not be the main virulence factor even in PVL strains. In the UK , PVL-positive MRSA have not been shown to spread more rapidly than any of the usual hospital-associated MRSA organisms. However, we will continue to monitor the situation.

Should patients be worried?

In the UK , there is no indication that current PVL-positive MRSA strains are more transmissible than other MRSA strains. Persons with recurrent skin infections – spreading inflammation (cellulitis), boils and abscesses – should seek medical advice. Standard treatment and infection control measures are highly effective.

What is the Health Protection Agency doing to ensure that PVL-positive MRSA does not become more widely spread?

At a local level, our Health Protection Units provide advice on infection control measures in the event of an incident or outbreak, as they do with other infectious diseases.

Eradication of S. aureus organisms is not possible, because there are no vaccines and patients are often not sufficiently immune after an infection. At least a third of people carry S. aureus as part of their normal bacterial flora, living on their skin or mucous membranes and causing no harm. However, when infection with such strains occurs, basic infection control measures are effective in preventing spread and available antibiotics are effective against them.

The Agency has published information to enable GPs and clinicians to recognise potential cases early and to then ensure that laboratory confirmation is obtained, treatment initiated early and infection control and hygiene advice implemented.

Guidance on the diagnosis and management of PVL-associated Staphylococcus aureus infections (PVL-SA) in England (PDF, 1.6 MB)  has now been published by the HPA. This guidance was prepared by a sub-group of the former Steering Group on Healthcare Associated Infection (SG-HCAI) at the request of the Department of Health. It replaces that drafted by Health Protection Agency (HPA) working group in 2006.

• Guidance on the diagnosis and management of PVL-associated Staphylococcus aureus infections (PVL-SA) in England (PDF, 1.6 MB)
  Report prepared by the PVL sub-group of the Steering Group on Healthcare Associated Infection
  Added/updated: 1 December 2010