A cryptic triptych (final) 120429

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  • Pathology Panton Valentin Leukocidin is a cytotoxin that can destroy white blood cells, leading to necrosis and severe infection Gene for PVL can be carried by both methicillin susceptible and resistant strains of staphylococcus aureus PCR test available to test for PVL gene Pathogenesis Asymptomatic carriage can occur Can present as boils, abscesses and necrotizing lesions Cellulitis Necrotising fasciitis Occasionally causing bacteraemia (which can lead to) Rarely necrotising pneumonia – high mortality rate of around 75% and can be transmitted through the respitatory route Epidemiology PVL-SA is not a new infection – first described by Panton and Valentine in the Lancet in 1932 <2% of SA isolates carry the gene for PVL Graph shows increasing numbers of PVL-SA isolates identified by the HPA reference laboratory – may be due to a combination of increased incidence and increased vigilance/reporting Treatment Treatment of susceptible infection is by flucloxacillin, erythromycin or clindamycin in the first instance Resistant strains may require combinations of antibiotics as appropriate to the susceptibility of the strain Prevention Risk factors for PVL infection include: Prevention of further cases can include tracing of close contacts at risk of infection, screening for carriage and decolonisation as required.
  • Prompted by HPZone, one of the first tasks was to establish whether there were any linked cases – there were none with shared context, postcode or within similar time periods. However, there was an enquiry which related to the same postcode. Enquiry related to severe mold in a rented student house where a total of six female student tenants reported a range of health problems including: Boils Asthma D&V Throat infection Nausea The enquiry had been referred to the local environmental health service and the deputy director of public health. The parents of the tenants had contacted the local press, MP and councilors. Tenants concerned that health problems were all related to the damp and mold. Ongoing legal dispute with the landlord.
  • Case 2 had only recently been transferred to our unit from Hertfordshire HPU. She had a three month history of recurrent boils and abscesses which had been treated, but there was some concern with regards to compliance as the antibiotics were not well tolerated. History suggests probably the index case. Was working in two different premises serving food and had been reluctant to be excluded. Reported that the boyfriend had similar boils/abscesses, but he had not been traced or contacted separately. Or had he???
  • Widened search and found case 3 - no links from contact tracing or postcodes but met age group of boyfriend of Case 2. All three cases were dealt with by different case managers and investigating officers.
  • Public health/infection control advice included: Regular bathing, Regular changing of bedlinen and underwear Hand washing Avoiding sharing personal items – cases and contacts had previously been sharing clothes Regular cleaning and good ventilation in same shared facilities Multiple decolonisations may be required
  • And an expectation that coincident cases would be self evident by the users of the system. In this scenario, contacts had not been traced and linked in the database, although there was some textual information relating to relationships between cases recorded in the event tables in relation to each case Identifying linked contacts may not be straightforward – the design of the HPZone queries does not allow for logical arguments or boolean operators or query across multiple fields or to include or exclude multiple values in each field. This means there is a need to run multiple queries to look for common values. Much of the information which allowed the cases to be linked in this case was gleaned from face to face interviews rather than over the phone conversations. Local GP registration has caused multiple issues, including obtaining prescriptions for decolonisation and meeting the ongoing healthcare needs of the cases. This finding is currently being further explored and we are looking at undertaking a local health needs assessment of university students in the city in partnership with NHS Bath & North East Somerset. The literature suggests SA can live on non-porous surfaces for in excess of five days.
  • It relies entirely on robust investigation, the quality of the information put into it and the consistent use of the correct fields for recording certain types of information which may be subsequently required to link cases in queries. This requires adherence to operational standards in using the database and some additional training may be required along with assurance through audit. This triptych, along with other recent investigations run in the HPU, highlights the fact that further development of the system is required to ensure that public health professionals can make the best use of the richness of information which is recorded in the HPZone system – both in operational outbreak control situations and to provide accurate public health intelligence. High caseload, large geographic operational areas and the availability of tools like HPZone may encourage a culture of remote/desktop investigation of situations rather than public health professionals taking their enquiries to the field. During this incident, a reliance on telephone interviews and remote investigation would have resulted in: Incomplete timeline of events A lack of understanding of the possible routes of transmission in the household and specific opportunities to A risk of following an inappropriate line of investigation around housing quality A missed opportunity to meet with close contacts of the cases in the round and answer questions


  • 1. A Cryptic TriptychThree seemingly unrelated cases of PVL-associatedStaphylococcus aureus infection, their investigationand managementDominic MellonSpecialty Registrar – Public HealthSouth West (North) Health Protection Unit
  • 2. Objectives• Review a series of three sporadic cases of PVL-SA• Discuss nature of the information available• Consider the role of HPZone in the investigation• Comment on issues arising from the investigation• Share learning and recommendations arising fromthis incident
  • 3. Panton-Valentin Leukocidin (PVL)associated Staphylococcus aureusSource: Health Protection Agency (2011) ‘PVL-Staphylococcus aureus infections: an update’, Health Protection Report, 5(7),[online] Available from: http://www.hpa.org.uk/hpr/archives/2011/news0711.htm#pvl (Accessed 24 April 2012).
  • 4. Case 1• Female student• 21 years old• Bath address/postcode, student rentedaccommodation• PVL-SA lab result reported to HPU on 8thFebruaryfollowing admission with abscess• Reporting clinician concerned that this is the thirdhousemate to be admitted, concerns around housingquality• No linked cases on HPZone
  • 5. Initial investigation• No geographically/temporally linked cases of PVL-SA• Case 3 shares a postcode with a previous enquiryabout damp, mold and health effects• Environmental Health Service had been involvedpreviously• Hospital visit and interview with Case 1 and parents• Began timeline of events• Queried HPZone for housemates
  • 6. Case 2 (probable index case)• Female student and food handler• 20 years old• Registered at GP practice in Hertfordshire,• Parent’s home address recorded• Recurrent boils and abscesses• Initially managed by Hertfordshire HPU• Transferred to South West (North) HPU 9thJanuary asterm time address is in Bath• No linked cases on HPZone
  • 7. Case 3• Male food handler• 21 years old• South Gloucestershire postcode, lives with parents• GP reported PVL-SA positive lab result 27thJanuaryfollowing swab at hospital the previous week• Treated in hospital for abscess on buttock• Girlfriend has had similar• HPU unable to contact case• No linked cases on HPZone
  • 8. Response• Visited student house to consider possible routes ofinfection• Arranged decolonisation for household contacts ofCases 1 and 2 (Case 3 already decolonised)• Provided public health/infection control advice• Did not consider further action required on the basisof housing quality
  • 9. Review• Conducted a tabletop review of the investigation andresponse to identify and share learning points
  • 10. Results• Over-reliance on HPZone to link cases together• Identifying linked cases may not be a straightfowardprocess and requires more than a cursoryassessment• Students may not be registered with local primarycare services or list term time addresses• Indirect transmission of the infectious agent mayhave played a significant role
  • 11. Conclusions• HPZone is a powerful tool, but it is only one toolavailable to the public health professional• HPZone has significant limitations in querying data• Sometimes it is important to get out from behind thedesk and leave the office to understand the situation
  • 12. ReferencesCavanagh, J., Quinn, M. and Wong, V. (2011) ‘Challenge of responding to PVL positive Staphylococcus aureus skininfection’, BMJ, 343(oct12 1), p. d6477-d6477, [online] Available from:http://www.bmj.com/cgi/doi/10.1136/bmj.d6477 (Accessed 13 February 2012).Gillet, Yves, Issartel, Bertrand, Vanhems, Philippe, Fournet, Jean-christophe, et al. (2002) ‘Mechanisms of DiseaseSeries: Association between Staphylococcus aureus strains carrying gene for Panton-Valentine leukocidin andhighly lethal necrotising pneumonia in young immunocompetent patients’, Lancet, 359, pp. 753-759, [online]Available from: http://www.sciencedirect.com/science/article/pii/S0140673602078777.Health Protection Agency (2009) ‘Boils and Skin Infections: Information for the public’, London, Health ProtectionAgency, [online] Available from: http://www.hpa.org.uk/webc/HPAwebFile/HPAweb_C/1287145721614.Health Protection Agency (2008) Guidance on the diagnosis and management of PVL-associated Staphylococcusaureus infections (PVL-SA) in England, London, [online] Available from:http://www.hpa.org.uk/webc/HPAwebFile/HPAweb_C/1218699411960.Health Protection Agency (2012) Management of PVL-Staphylococcus aureus: Recommendations for Practice, London,[online] Available from: http://www.hpa.org.uk/webc/HPAwebFile/HPAweb_C/1267551719486.Health Protection Agency (2011) ‘PVL-Staphylococcus aureus infections: an update’, Health Protection Report, 5(7),[online] Available from: http://www.hpa.org.uk/hpr/archives/2011/news0711.htm#pvl (Accessed 24 April 2012).Knott, Lawrence (2010) ‘PVL-positive Staphylococcus Aureus’, Patient.co.uk, [online] Available from:http://www.patient.co.uk/doctor/Panton-Valentine-Leukocidin-(PVL)-Positive-Staph.-Aureus.htm (Accessed 24 April2012).Millership, S, Cummins, A, Irwin, D, Kearns, A and English, P (2011) ‘Follow up of cases of PVL-positive Staphylococcusaureus is not worthwhile.’, The Journal of Infection, The British Infection Association, 62(3), pp. 234-5, [online]Available from: http://www.ncbi.nlm.nih.gov/pubmed/21281674 (Accessed 13 February 2012).Panton, P N and Valentine, F C O (1932) ‘Staphyloccocal Toxin’, The Lancet, 219(5662), pp. 506-508, [online] Availablefrom: http://www.sciencedirect.com/science/article/pii/S0140673601244687.
  • 13. Any questions?dominic.mellon@nhs.net