Objective: the aim of this study was to establish at which point during a hospital admission MRSA acquisition occurs in vascular patients.
Method: a consecutive series of 100 patients undergoing arterial surgery were screened for MRSA carriage on admission to hospital, on exit from theatre, on discharge from ITU, weekly whilst an inpatient and on hospital discharge. Screening was with moistened swabs from nose, throat, perineum and open wounds that were pooled for microbiological culture.
Results: four patients (4%) screened positive for MRSA on admission to hospital. Of the remaining 96, 16 (17%) acquired MRSA during their hospital stay as follows: exit from theatre, one; exit from ITU, six; on the ward postoperatively, nine. Comparing MRSA acquisition (n=16) with non acquisition (n = 80) the following characteristics were noted, length of stay 16 (4-66) vs 7 (2-50) days (Mann-Whitney p < 0.001); admission to ITU 13/16 vs 46/80 (Fishers chi-squared p = 0.10); length of ITU stay 3 (1-20) vs 3 (1-14) days (Mann-Whitney p = 0.41). Frequent hospital attendance, age, emergency admission, diabetes or renal failure were not commoner in those with MRSA acquisition.
Conclusions: these data indicate that 4% of patients undergoing arterial surgery are pre-existing carriers of MRSA. Length of hospital stay is the single most important determinant of MRSA acquisition.