Our Trust's prophylactic antibiotic regime for elective hip and knee replacements recently changed, following the publication of Department of Health guidelines aimed at reducing the incidence of Clostridium Difficile associated diarrhoea (CDAD). We aimed to assess whether this change has reduced the incidence of post-operative CDAD.

We reviewed all primary and revision total hip and knee replacements performed in Gloucestershire Royal Hospital between April 2007 and March 2010. Up to August 2008, patients received prophylaxis with cefuroxime (Group A). This subsequently changed to flucloxacillin and gentamicin (Group B). All patients who developed CDAD within one month of surgery were identified and their case-notes were reviewed for the presence of CDAD risk factors, such as concomitant use of broad-spectrum antibiotics.

3117 patients were included and 15 developed CDAD (0.48%); 12 patients (0.77%) from Group A and 3 from Group B (0.19%), representing a four-fold decrease. Analysis of a 2×2 contingency table with Fisher's exact test showed that the difference between the two groups was statistically significant (P=0.0347).

Case-note analysis revealed that 8/12 patients in Group A and 1/3 patients in Group B had other risk factors for developing CDAD. Excluding these patients, the difference between the two groups was not statistically significant (P=0.218).

CDAD is exceedingly rare following total joint replacement surgery, especially when the only antibiotics given are prophylactic. Our figures are in line with a general decline in CDAD nationally from 2007. This decline is most likely due to multiple factors, such as hand-washing, barrier nursing and restrictive antibiotic policies. The effect of the change in prophylaxis is therefore difficult to quantify. Choice of prophylactic antibiotics should be based upon their efficacy alone, not their potential to reduce CDAD.