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Outbreak of prosthetic valve endocarditis | Signal

Reference number
Issue date25 March 2011

This Signal is about the investigation into an outbreak of prosthetic valve endocarditis in Trent Cardiac Centre, (TCC) Nottingham University Hospitals NHS Trust (NUH).

In 2009, eleven patients developed early prosthetic valve endocarditis (PVE). Five patients died and of the surviving patients, five underwent a total of seven reoperations. The patients had been operated on by the same cardiac surgeon in whom there was no evidence of shortcomings in skill, technique or previous unusual infective complications.

The PVE organism was a Staphylococcus epidermidis, resistant to standard prophylactic antibiotics. The surgeon’s skin had become unknowingly colonised by the outbreak strain. The exact mode of transmission is unestablished but it is likely it was from the surgeon directly to the valve during surgery. There were no cases after the surgeon stopped undertaking valve operations, and prophylactic antibiotics were changed. Until this outbreak the TCC had a low rate of PVE (NUH 0.35 per cent, UK 1-3 per cent).

Similar Staphylococcus epidermidis strains had caused isolated cases of PVE in 2006, 2007, and 2008 (other surgeons). Other surgeons, and staff, at the TCC and NUH (and probably the wider NHS) are colonised with similar bacteria (though none were carrying the genetically distinct outbreak strain). Opportunities were missed to identify the outbreak (and avoid cases) because information about the clinical progress and laboratory results of patients after cardiac surgery was not effectively shared between clinicians, clinical teams, hospitals, and laboratories.

Actions taken by the Trust following the incident:

1. TCC antibiotic resistance and prophylaxis will be reviewed annually.
2. Mupirocin nasal cream is now, where possible, restricted to carriers of Staphylococcus aureus (MSSA and MRSA).
3. More effective separation of pre-operative and post-operative patients.
4. PVE risk explained when consent taken for cardiac valve surgery.
5. Double or thick gloves for cardiac surgery. If changing gloves intra-operatively this is by down-gloving or open-glove changing, rather than the closed glove technique.  
6. Clinical staff must actively consider PVE in all valve patients who return to GP or hospital with relevant symptoms. Assessment must include blood cultures (if within one year of surgery) and senior clinical review before discharge.
7. Wherever patients present, clinical staff must promptly report post-operative symptoms to the operating cardiac surgeon, and microbiology results to the NUH infection control doctor.
8. All actual or suspected cases of PVE are subject to formal review and discussion at the next cardiac multi-disciplinary team and Morbidity and Mortality meetings.

The Trust aims  to undertake and commission work to explore possible transmission mechanisms between surgeons and patients, the relationship between the use of topical and prophylactic antibiotics and the development of antibiotic resistance, and the implications of colonisation for surgeons and other staff involved in surgery.

Please contact the Trust at safety@nuh.nhs.uk with any initiatives to reduce risk in these areas.

This Signal emerged from a local investigation carried out by the Trust and at their request is being shared by the NPSA for wider national learning.