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Volume 5 No 7; 18 February 2011
PVL–Staphylococcus aureus infections: an update
Strains of Staphylococcus aureus encoding the PVL genes (PVL-SA) have been recognised as a cause of infection in community and healthcare settings world-wide for over 60 years. Originally universally susceptible to methicillin, interest in PVL-SA increased following the emergence, in the 1990s, of methicillin resistant strains which have become known as PVL-MRSA or community-associated MRSA (CA-MRSA).
Over the last two decades, PVL-MRSA have been observed internationally with increasing frequency. Some countries report high rates of a particular clone of CA-MRSA being dominant, for example USA [1], Greece [2] and Australia [3] where the so-called USA300, European and Queensland clones, respectively, predominate. In contrast, other countries (including England) report a variety of different clones circulating [1,4].
Situation in England and recent trends
Annual figures for PVL-SA identified in England by the HPA Staphylococcus Reference Unit (SRU) showed an upward trend between 2005 and 2008 [5], with a reducing rate of increase being seen subsequently. In the table and figure below, this series of data is updated to 2010 – the apparent decline in reports in that year probably reflecting a new element of under-reporting as an increasing number of centres are testing for PVL locally.
Number of PVL–SA identified by the HPA's Staphylococcus Reference UnitYear |
No. (%) PVL-MSSA |
No. (%) PVL-MRSA |
Total PVL-SA |
Relative change year-on-year |
2005 |
107 (48%) |
117 (52%) |
224 |
|
2006 |
337 (68%) |
159 (32%) |
496 |
+ 2.2-fold |
2007 |
729 (60%) |
477 (40%) |
1206 |
+ 2.4-fold |
2008 |
1013 (58%) |
724 (42%) |
1737 |
+ 1.4-fold |
| 2009 | 1573 (61.5%) |
984 (38.5%) |
2557 |
+ 1.5-fold |
| 2010 | 1178 (53%) |
1049 (47%) |
2227 |
- 0.87-fold |
Number PVL–SA identified by the HPA's Staphylococcus Reference Unit
From 2006 onwards, the majority of PVL-SA identified have been susceptible to methicillin.
It is not clear whether the overall increase in PVL-SA in recent years in England has been due to improved awareness and case recognition, allied to pro-active close contact tracing, or whether it reflects a genuine increase in PVL-SA nationally. Ongoing systematic surveillance-based studies funded by DH will provide more robust data for monitoring trends to investigate the prevalence of PVL-SA in the community.
Management and surveillance
PVL-SA most commonly cause pyogenic skin infections (eg boils and abscesses) which generally require treatment with incision and drainage and/or antibiotics [6]. Analysis of SRU data shows that 65% of S. aureus from such infections are PVL-positive, one third of which are associated with recurrent episodes of infection.
Whilst cases are mainly sporadic and community-associated, outbreaks in healthcare settings have been observed in England and abroad [1,7,8]. The molecular epidemiology of CA-MRSA is complex: many different lineages of PVL-SA have been identified in England and world-wide [1,4] some of which are multiply antibiotic resistant [9].
Algorithm for microbiological testing
MSSA or MRSA from patients with the following clinical features should be considered for PVL-testing [5]:- boils or abscesses, especially where these are recurrent;
- necrotising skin and soft tissue infections ;
- necrotising pneumonia, purpura fulminans or necrotising fasciitis; or
- isolates from close contacts of PVL cases (where the antibiogram corresponds with that of the PVL-SA found in the index case).
It remains important to monitor which strains are circulating, track disseminated clones and monitor for the emergence of new or emerging strains. The SRU also welcomes the referral of PVL-SA for characterisation and to assist with suspected outbreak investigations [10].
Suitable isolates should be forwarded for investigation to: Staphylococcus Reference Unit, Microbiology Services Division, HPA, 61 Colindale Avenue, London NW9 5HT, accompanied by the appropriate request forms [11] which should be completed as fully as possible, including PVL status (if known), clinical information and antibiotic susceptibility data.
References
1. David MZ, Daum RS. Community-Associated Methicillin-Resistant Staphylococcus aureus: Epidemiology and Clinical Consequences of an Emerging Epidemic. Clin Microbiol Rev 2010; 23:616-687.
2. Vourli S, Vagiakou H, Ganteris G, Orfanidou M, Polemis M, Vatopoulos A, Malamou-Ladas H. High rates of community-acquired, Panton-Valentine leukocidin (PVL)-positive methicillin-resistant S. aureus (MRSA) infections in adult outpatients in Greece. Euro Surveill 2009; 14(2). Available online: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19089.
3. Nimmo GR, Coombs GW. Community-associated methicillin-resistant Staphylococcus aureus (MRSA) in Australia. Int J Antimicrob Agents 2008; 31: 401-410.
4. Ellington MJ, Perry C, Ganner M, Warner M, McCormick Smith I, Hill RL, Shallcross L, Khatri K, Sabersheikh S, Holmes A, Cookson BD, Kearns AM. Clinical and molecular epidemiology of ciprofloxacin-susceptible MRSA encoding PVL in England and Wales. Eur J Clin Micro Inf Dis, 2009; 28:1113-1121.
5. Health Protection Agency. PVL-SA infections in England and Wales: 2005-2008 data and revised algorithm for referral of suspected cases Health Protection Report 2009; 3(35): news.
6. Guidance on the diagnosis and management of PVL-associated Staphylococcus aureus infections (PVL-SA) in England. HPA website: Home > Topics > Infectious Diseases > Infections A-Z > Staphylococcus aureus > Guidelines > Staphylococcus aureus Guidelines [1.6 MB PDF].
7. Orendi JM, Coetzee N, Ellington MJ, Boakes E, Cookson BD, Hardy KJ, Hawkey PM, Kearns AM. Community and nosocomial transmission of Panton-Valentine leukocidin-positive community-associated MRSA: implications for healthcare. J Hosp Infect 2010; 75:258-264.
8. Teare L, Shelley OP, Millership S, Kearns A. Outbreak of Panton-Valentine Leucocidin-positive Meticillin Resistant Staphylococcus aureus in a regional burns unit. J Hosp Infect 2010; 76:220-224.
9. Ellington MJ, Ganner M, Warner M, Cookson BD, Kearns AM. Polyclonal multiply antibiotic-resistant methicillin-resistant Staphylococcus aureus with Panton-Valentine leucocidin in England. J Antimicrob Chemother 2010; 65:46-50.
10. Staphylococcus Reference Unit, HPA Microbiology Services Division, Colindale. Contact Dr Angela Kearns (tel: 0208-3277227; e-mail: angela.kearns@hpa.org.uk).
11. Available from the HPA website at: Home › Products & Services › Infectious Diseases › Laboratories and Reference Facilities › Laboratory of HealthCare Associated Infection (LHCAI) › Request Forms H1, H2 and H3.