Bacterial colonisation of Doppler probes on vascular surgical wards

Aim: hospital acquired infections cost the NHS 1 billion each year and medical equipment may act both as source and vector of nosocomial infection. This study examined bacterial contamination of Doppler ultrasound probes (USP) in routine use on vascular surgical wards in six hospitals and the knowledge of staff about the potential for cross infection from contaminated probes. Methods: probe head impressions and swab cultures of probe holders were plated on mannitol salt agar before and after cleaning with a paper towel. Putative S. aureus isolates were identified to species level and susceptibility to selected antimicrobials tested. Concurrently, junior medical staff were surveyed about probe cleaning protocols. Results: methicillin susceptible S. aureus was isolated from 2/21 (10%) with near confluent bacterial growth from six others (28%). The latter may have obscured low numbers of S. aureus. Further since swabs were plated without prior enrichment culture, it is likely that contamination with S. aureus might have been underestimated. No positive cultures were obtained after wiping the USP with a paper towel. 22/23 (95%) junior doctors failed to clean the USP prior to use. Conclusion: USP contamination with pathogenic bacteria occurs under "in-use" conditions and junior medical staff are unaware of simple measures to prevent this. Strict guidelines for USP cleaning between patient use should, therefore, be adopted particularly when monitoring postoperative graft patency.