A safe and practical decontamination method to reduce the risk of bacterial colonization of ultrasound transducers

A multicenter study on the effects of different methods of disinfecting medical external-use ultrasound probes

BACKGROUND

Microbial contamination of external-use ultrasound probes is a serious and overlooked issue. We assessed the effects of different methods of disinfecting medical external-use ultrasound probes.

METHODS

On-site disinfection experiments were conducted at 10 hospitals; the tips and sides of external-use ultrasound probes were sampled before and after disinfection, and 3 disinfection methods were assessed (use of a new ultraviolet [UV] ultrasound probe disinfector, wiping with ordinary paper towels or cleaning with disinfectant wipes).

RESULTS

For the new UV probe disinfector, the median microbial death rates for the tips and sides of the external-use ultrasound probe were 93.67% and 97.50%, respectively, which were higher than those for wiping with paper towels and cleaning with disinfectant wipes (12.50% and 10.00% and 20.00% and 21.42%, respectively); the rates of microorganisms exceeding the standard were 15.0% and 13.3%, respectively, which were lower than those for wiping with paper towels and cleaning with disinfectant wipes (53.3% and 60.0% and 46.7% and 38.3%, respectively). The death rates of different species of microorganisms were high, ranging from 87.5% to 100%.

CONCLUSIONS

The new UV ultrasound probe disinfector significantly reduced the risk of potential nosocomial infections according to the low microbial death rate for conventional disinfection methods.

Experimental Observation of Isolative Efficacy of a Solid Coupling Medium in Extracorporeal Shock Wave Lithotripsy—Implications to Nosocomial Infection Prevention

Introduction: Extracorporeal shock wave lithotripsy (ESWL) is a well-established, popular treatment choice for renal stones. Traditionally, the semi-liquid gel is used as a coupling medium in ESWL. During ESWL, body fluid or blood might transmit between the patients when the probe or gel used in the procedure is contaminated and cause potential nosocomial infections. To solve this problem, we developed a solid coupling medium (isolation coupling pad, referred to as “icPad”) between the patient’s skin and the probe as a shock wave transmission medium to prevent contamination. This study aimed to investigate the isolative efficacy of the icPad in blocking the permeation of microbes. Method: Rhodamine 6G (a fluorescent dye) was used as a tracer to simulate the microorganisms. The penetration of the fluorescent dye on the longitudinal section of the icPad was observed by a microscope after the dye was placed on the body side of the icPad for 40 min. After the shock wave, icPad was extracted with 75% ethanol, and fluorescence intensity was measured with a fluorescence spectrometer. Results: Our results revealed that the body side of icPad is free of fluorescent dye during lithotripsy. Qualitative analysis results confirmed that icPad has an isolative effect on simulating contaminants such as bacteria or viruses. Conclusion: In this in vitro phantom study, a proprietary icPad can be an isolative coupling medium and is speculated to avoid cross-contamination of bacterial or viral infection during ESWL.

Identification and Analysis of Bacterial Contamination of Ultrasound Transducers and Multiuse Ultrasound Transmission Gel Bottle Tips Before and After the Aseptic Cleansing Technique

OBJECTIVES

To provide a descriptive analysis for species identification of culture and Gram stain results from ultrasound transducers and multiuse ultrasound transmission gel bottle tips in active clinical use and to compare bacterial cultures from ultrasound transducers before and after aseptic cleansing.

METHODS

A prospective blinded descriptive analytic study of 18 distinct clinical care sites within a single primary clinical institution was conducted. Before and after a disinfectant towel cleanse, transducers were pressed against tryptic soy agar contact plates. Plates were deidentified and submitted for blind incubation, Gram staining, and species identification with microsequencing. Results were classified as clinically relevant (CR) or non-clinically relevant. In total, 188 samples were analyzed: 80 from ultrasound transducers before and cleansing, 13 from multiuse gel bottle tips before and after cleansing, and 2 precleansing samples from the data collector's pen and badge.

RESULTS

Fifty-nine precleansing samples (73.8%) grew cultures with CR bacteria, and 21 samples (26.3%) did not. Staphylococcus simulans represented 31.0% of all positive culture samples. Thirteen postcleansing samples (16.3%) grew cultures with CR bacteria, equating to a 78.0% reduction of CR bacterial growth (likelihood ratio, 57.10; P < .001).

CONCLUSIONS

Ultrasound transducers have a notable CR bacterial burden and may serve as potential infective vectors. Aseptic cleansing effectively eliminates most of the bacterial load from ultrasound transducers, but some bacteria persist, presenting a risk of nosocomial infection with ultrasound-guided interventions. These findings support American Institute of Ultrasound in Medicine 2018 guidelines intended to ensure an appropriate level of transducer preparation based on the examination type while emphasizing rational infection control measures to minimize the risk of potential patient harm.

Infection prevention and control in ultrasound - best practice recommendations from the European Society of Radiology Ultrasound Working Group

OBJECTIVES

The objective of these recommendations is to highlight the importance of infection prevention and control in ultrasound (US), including diagnostic and interventional settings.

METHODS

Review of available publications and discussion within a multidisciplinary group consistent of radiologists and microbiologists, in consultation with European patient and industry representatives.

RECOMMENDATIONS

Good basic hygiene standards are essential. All US equipment must be approved prior to first use, including hand held devices. Any equipment in direct patient contact must be cleaned and disinfected prior to first use and after every examination. Regular deep cleaning of the entire US machine and environment should be undertaken. Faulty transducers should not be used. As outlined in presented flowcharts, low level disinfection is sufficient for standard US on intact skin. For all other minor and major interventional procedures as well as all endo-cavity US, high level disinfection is mandatory. Dedicated transducer covers must be used when transducers are in contact with mucous membranes or body fluids and sterile gel should be used inside and outside covers.

CONCLUSIONS

Good standards of basic hygiene and thorough decontamination of all US equipment as well as appropriate use of US gel and transducer covers are essential to keep patients safe.

MAIN MESSAGES

• Transducers must be cleaned/disinfected before first use and after every examination. • Low level disinfection is sufficient for standard US on intact skin. • High level disinfection is mandatory for endo-cavity US and all interventions. • Dedicated transducer covers must be used for endo-cavity US and all interventions. • Sterile gel should be used for all endo-cavity US and all interventions.

Bacterial contamination of ultrasound probes in different radiological institutions before and after specific hygiene training: do we have a general hygienical problem?

OBJECTIVES

Aim was to investigate hygienic conditions of ultrasound probes before and after hygiene training in radiology institutions in comparison to bacterial contamination in public places.

METHODS

In three radiology departments, bacterial contamination was evaluated using baseline agar plates for cultures taken from 36 ultrasound probes. Afterwards teams were trained by a hygiene service centre and 36 ultrasound probes were routinely disinfected with regular disinfecting wipes and then evaluated. In comparison, bacterial contamination in public places (bus poles, n = 11; toilet seats, n = 10) were analysed. Plates were routinely incubated and the number of colony forming units (CFU) analysed.

RESULTS

Cultures taken from the probes showed a median of 53 CFU before and 0 CFU after training (p < 0.001). Cultures taken from public places showed a median of 4 CFU from toilets and 28 from bus poles and had lower bacterial load in comparison to ultrasound probes before training (p = 0.055, toilets; p = 0.772, bus poles), without statistical significance.

CONCLUSIONS

Bacterial contamination of ultrasound probes prior to hygiene training proved to be high and showed higher bacterial load than toilets seats or bus poles. Radiologists should be aware that the lack of hygiene in the field of ultrasound diagnostics puts patients at risk of healthcare-associated infections.

KEY POINTS

• Hospital-associated infections are a problem for patient care. • Hygiene training of staff prevents bacterial contamination of ultrasound probes. • Disinfection of ultrasound probes is an easy method to protect patients.

Emergency department ultrasound probe infection control: challenges and solutions

Point-of-care ultrasound (US) has become a cornerstone in the diagnosis and treatment of patients in the emergency department (ED). Despite the beneficial impact on patient care, concern exists over repeat use of probes and the role as a vector for pathogen transmission. US probes are used for various applications, with the level of infection risk, based on the Spaulding Classification, ranging from noncritical with common practice to semicritical with endocavitary probes. To date, the most closely studied organisms are Staphylococcus aureus and human papilloma virus. Current evidence does confirm probe colonization but has not established a causative role in human infection. Based on current literature, US use during invasive procedures remains an infection control concern, but routine use on intact skin does not appear to cause significant risk to patients. Various barrier methods are available, each with indications based on extent of procedure and likelihood of contact with mucosal surfaces. Additionally, chemical cleansing methods have been shown to be effective in limiting probe contamination after use. New technologies utilizing ultraviolet light are available and effective but not widely used in the ED setting. As our understanding of the critical factors in US probe cleaning and disinfection improves, it is important to assess the challenges found in our current practice and to identify potential solutions to improve practices and procedures in infection control across the spectrum of US probe use in various applications in the ED. This article serves as a summary of the current literature available on infection control topics with the utilization of point-of-care US, and discusses challenges and potential solutions to improve the current practice of probe-related infection control.