An Investigation of the Bacterial Contamination of Ultrasound Equipments at a University Hospital in Saudi Arabia

Objective: Nosocomial infections present a widespread problem in today's healthcare environment, with a significant number of patients acquiring an infection annually. With the contemporary transition of immunocompromised and high-risk patients to community-based care, ultrasound has the potential to be a vector of infection in the Radiology setting. The purpose of the present study was to determine the degree of contamination on ultrasound equipment and gel after routine clinical use and to determine the effectiveness of three different methods of ultrasound probe cleaning for the prevention of nosocomial infections. Methods: A total of 444 culture swabs from different parts of the three ultrasound machines and from the gels were taken. All samples were tested in a microbiology laboratory at King Khalid University Hospital, Riyadh, Saudi Arabia, using different culture media. The isolates were identified by using standard techniques. All isolates were subjected to antimicrobial susceptibility testing using the Kirby-Bauer disc diffusion technique on Muller-Hinton agar and commercial antibiotic discs were used for antimicrobial testing. In addition to this, MIC was performed for all isolates according to the Clinical and Laboratory Standards Institute (CLSI) interpretative criteria. Results: The majority of organisms which are found in normal skin and environmental flora were isolated from different parts of the ultrasound machines. The gels were heavily contaminated with opportunistic and potentially pathogenic organisms like Staphylococcus aureus and Enterococcus faecalis. No multi-resistant organisms were identified. There was a significant reduction in the bacterial count after applying either of all the three cleaning methods for the ultrasound probe as compared to the count on the probes before cleaning (p<0.001). However, the soap cleaning method was the most effective one in decreasing the bacterial count to the minimum level in comparison to other two methods (p<0.001). The overall reduction in the pathogenic bacterial count after performing each cleaning method was 46%, 75% and 97% for the paper cleaning, the normal saline and the soap cleaning methods, respectively. Conclusion: The non-invasive ultrasound equipment is a potential vector for nosocomial infection in Radiology patients. Cleaning the ultrasound probe after performing each procedure is a costeffective practice with a potential for reducing nosocomial infections. The soap cleaning technique is the most effective method for reducing the bacterial count which is acquired due to the patients' body contact with the ultrasound probes. Further research into the possible strategies to reduce the risk of infection from the ultrasound gels is needed.