Background: Bacterial contamination of medical equipment is a serious problem. If effective cleaning methods are not employed, sonographic examinations performed in the emergency department can lead to patient-to-patient transmission of pathogens.

Objective: To compare the effectiveness of four different ultrasound probe cleaning methods in reducing bacteria and to determine the types of bacteria found on ultrasound probes.

Materials and Methods: This was a randomized experimental study. The sample consisted of 104 ultrasound probes used at the Srinagarind Hospital emergency department from August 2019 to December 2019. Probes were randomized into four groups of 26. Cultures were examined before and after cleaning using one of four different techniques including wiping with a dry paper towel or washing with liquid soap, 4% chlorhexidine gluconate, or dimethyl ammonium chloride. Quantitative grading of bacterial colonies was performed to determine cleaning effectiveness.

Results: All four cleaning method resulted in significant reductions in bacteria (p<0.001), but 4% chlorhexidine gluconate was the most effective (no bacterial growth in 84.62% of cases; p<0.001). The bacteria found were Staphylococcus coagulase-neg, Pseudomonas spp., Bacillus spp., Micrococcus spp., and Corynebacterium. We also found fungus on two of the ultrasound probes.

Conclusion: The authors found many types of bacterial contamination on the surfaces of ultrasound transducers. Cleaning probes after performing sonographic examination is necessary. Based on both its ability to control infection control and its cost-effectiveness, 4% chlorhexidine gluconate is recommended.

Keywords: Cleaning methods, Ultrasound, Emergency department, Disinfection