An audit of Staphylococcus aureus bacteraemia in a single renal unit

J Ismail, L Fitch, K Alshafi, K Farrington, P Warwicker

Lister Hospital, Stevenage

Problem Access to a reliable, convenient and safe source of blood is an essential pre-requisite to haemodialysis. The gold standard is the AV fistula. Renal units in the United Kingdom usually fall far short of this gold standard. In our dialysis units there has historically been a chronic under-provision of vascular access surgery leading to a reliance on tunnelled central venous catheters (CVCs).

Vascular access-related septicaemia is the most common cause of morbidity and second commonest cause of death in the US dialysis population. Staphylococcus aureus is the bacterium most often related to vascular access-related septicaemia in haemodialysis patients. The incidence of hospital acquired methicillin resistant S. aureus (MRSA) continues to rise both in the UK and globally.

Purpose To audit the incidence, cause, consequences and outcomes of S. aureus bacteraemias in a single renal unit

Design We have retrospectively analysed all recorded S. aureus bacteraemias over the last 34 months in our unit.

Findings There were 128 episodes of S. aureus bacteraemia recorded in 84 patients (34 months of follow up) representing 35% of all the recorded episodes in the hospital. Of these there were 36 episodes of MRSA septicaemia in 22 patients, and 92 episodes of MSSA septicaemia in 62 patients. During the period of follow up mortality was high (31%) and especially so in the patients with MRSA bacteraemia (50%).

Of the 128 episodes of bacteraemia, only 22 occurred in patients with AV fistulas and grafts, despite this making up approximately 60% of the dialysis population; whereas 104 occurred in patients with CVCs (2 other causes). Only 3 of the 22 patients suffering MRSA bacteraemia were dialysing using an AV fistula

Conclusion Our audit has demonstrated a worrying number of Staphylococcus aureus bacteraemias over a period of 34 months in a moderately sized renal service. In addition there appears to be a significantly increased risk of bacteraemia in patients with central venous catheters, with a legacy of increased mortality. We do not believe that our figures are unrepresentative of the picture in the rest of the UK, although our low proportion of AV fistulae is amongst the lowest, and far below European standards.

Relevance Attempts to control the spread of MRSA and MSSA have principally relied on three measures, namely, hand hygiene amongst healthcare staff, detection and isolation of infected or colonised patients and restriction of antibiotics. The current dependence on tunnelled central venous catheters for vascular access, threatens these central principles of care. Patients with tunnelled central catheters are more likely to become infected with Staphylococcus species. Our limited isolation facilities are unlikely to cope with proportions of haemodialysis patients with central catheters nearing fifty percent, and vancomycin cannot be withheld from a septicaemic ill dialysis patient.

We anticipate a second tidal wave on the horizon - of glycopeptide resistant S.aureus strains, further limiting therapeutic options, unless drastic steps are taken soon to address the shortfall in vascular access provision in the UK.