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.

Can diagnostic ultrasound scanners be a potential vector of opportunistic bacterial infection?

UNLABELLED: Ultrasound examinations are recognised as being safe. The greatest epidemiological threat during the performance of examination is the transfer of pathogenic and opportunistic microorganisms between patients and from personnel to patients. Colonization of the skin with opportunistic bacteria of immunocompromised and high risk patients may lead to infection following an ultrasound scan. AIM: To identify and evaluate the strains of bacteria occurring on ultrasound equipment subjected to unexpected control performed by a local infectious diseases control team. We assumed that transducers, gel holders and gel bottles can be contaminated with normal human skin microflora. The remaining tested parts of the ultrasound equipment could possibly be contaminated with normal human skin microflora and other pathogens. MATERIAL AND METHODS: The swabs were taken from ultrasound scanners located in various hospital settings, from out-patient based radiology scanning rooms to operating theatre, and cultured. RESULTS: Among all isolated 23% strains were classified as environmental microflora; 8% as strains related to patient's skin contamination; and 13 % strains constituted pathogenic Gram-negative rods.. The remaining strains were classified as opportunistic flora 38%. High prevalence of opportunistic bacteria cultured in our study lead to the modification of the ultrasound cleaning procedures in both institutions and recommendation of the use of antibacterial wipes to clean all parts of ultrasound equipment in contact with patients' skin and examiners. CONCLUSIONS: Contamination not only affects parts of diagnostic equipment placed in direct contact with the patient, but also, those surfaces that only medical personnel have had contact with.

Disinfection of transvaginal ultrasound probes in a clinical setting: comparative performance of automated and manual reprocessing methods.

OBJECTIVES: Transvaginal and intracavitary ultrasound probes are a possible source of cross-contamination with microorganisms and thus a risk to patients' health. Therefore appropriate methods for reprocessing are needed. This study was designed to compare the standard disinfection method for transvaginal ultrasound probes in Germany with an automated disinfection method in a clinical setting. METHODS: This was a prospective randomized controlled clinical study of two groups. In each group, 120 microbial samples were collected from ultrasound transducers before and after disinfection with either an automated method (Trophon EPR®) or a manual method (Mikrozid Sensitive® wipes). Samples were then analyzed for microbial growth and isolates were identified to species level. RESULTS: Automated disinfection had a statistically significantly higher success rate of 91.4% (106/116) compared with 78.8% (89/113) for manual disinfection (P = 0.009). The risk of contamination was increased by 2.9-fold when disinfection was performed manually (odds ratio, 2.9 (95% CI, 1.3-6.3)). Before disinfection, bacterial contamination was observed on 98.8% of probes. Microbial analysis revealed 36 different species of bacteria, including skin and environmental bacteria as well as pathogenic bacteria such as Staphylococcus aureus, enterobacteriaceae and Pseudomonas spp. CONCLUSIONS: Considering the high number of contaminated probes and bacterial species found, disinfection of the ultrasound probe's body and handle should be performed after each use to decrease the risk of cross-contamination. This study favored automated disinfection owing to its significantly higher efficacy compared with a manual method. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Impact of vaginal-rectal ultrasound examinations with covered and low-level disinfected transducers on infectious transmissions in france.

BACKGROUND: The risk of cross-infection from shared ultrasound probes in endorectal and vaginal ultrasonography due to low-level disinfection (LLD) is difficult to estimate because potential infections are also sexually transmitted diseases, and route of contamination is often difficult to establish. In France, the widely used standard for prevention of infections is through the use of probe covers and LLD of the ultrasound transducer by disinfectant wipes. We performed an in silico simulation based on a systematic review to estimate the number of patients infected after endorectal or vaginal ultrasonography examination using LLD for probes. STUDY DESIGN: We performed a stochastic Monte Carlo computer simulation to produce hypothetical cohorts for a population of 4 million annual ultrasound examinations performed in France, and we estimated the number of infected patients for human immunodeficiency virus (HIV), herpes simplex virus, hepatitis B virus, hepatitis C virus, human papilloma virus, cytomegalovirus, and Chlamydia trachomatis. Modeling parameters were estimated by meta-analysis when possible. RESULTS: The probability of infection from a contaminated probe ranged from 1% to 6%, depending on the pathogen. For cases of HIV infection, this would result in approximately 60 infected patients per year. For other common viral infections, the number of new cases ranged from 1,600 to 15,000 per year that could be attributable directly to ultrasound and LLD procedures. CONCLUSIONS: Our simulation results showed that, despite cumulative use of probe cover and LLD, there were still some cases of de novo infection that may be attributable to ultrasound procedures. These cases are preventable by reviewing the currently used LLD and/or upgrading LLD to high-level disinfection, as recommended by the US Centers for Disease Control and Prevention.

Bacterial contamination of ultrasound probes at a tertiary referral university medical center.

OBJECTIVE: The purpose of this study was to assess the adequacy of our institution's ultrasound probe-disinfecting protocols, determine compliance with the guidelines, and then implement changes if needed. MATERIALS AND METHODS: We first assessed the prevalence of bacterial contamination (and thus the potential for bacterial transmission) by swabbing all ultrasound probes (n = 31) in the radiology department and culturing the samples. Next, in conditions simulating the typical work environment, we determined the efficacy of our probe-disinfecting protocols by seeding probes with 10(4)-10(9) CFU/mL of methicillin-resistant Staphylococcus aureus (MRSA), disinfecting the seeded probes with 0.5% accelerated hydrogen peroxide, and then swabbing the disinfected probes to assess for bacterial growth. RESULTS: Seven of 31 (22.6%) probes were positive for bacterial growth--none of which were endocavity probes (0/4). Four of 14 visibly soiled probes (28.6%) showed bacterial growth, and four of seven probes positive for bacteria (57.1%) were visibly soiled. No MRSA grew after seeding probes with MRSA and then disinfecting with 0.5% accelerated hydrogen peroxide. Sonography guidelines and general disinfecting guidelines were reviewed. CONCLUSION: Our protocols for disinfecting nonendocavity and endocavity probes are compliant with sonography guidelines and general disinfecting guidelines. Although limited by a small sample size, our study showed that our protocol for disinfecting endocavity probes seems adequate. With a 25.9% bacterial contamination rate for nonendocavity probes, the adequacy of our protocol for disinfecting nonendocavity probes is more debatable; however, this bacterial contamination rate is at the lower end of the values reported in the literature. With the use of an effective disinfectant, education of sonographers, and implemented changes, we hope to decrease bacterial contamination rates and thus decrease the potential for bacterial transmission.

Physical therapy clinic therapeutic ultrasound equipment as a source for bacterial contamination.

A procedure commonly used in physical therapy (PT) clinics is therapeutic ultrasound (US). This equipment and associated gel comes in contact with patient skin, potentially serving as a reservoir for bacteria. In this study, we sampled US heads, gel bottle tips and gel from nine outpatient PT clinics in Southeastern Tennessee. Samples were collected using sterile swabs. At the microbiology laboratory, these swabs were used to inoculate mannitol salt agar and CHROM-MRSA agar (for Staphylococcal species) and tryptic soy broth to determine non-specific bacterial contamination. US heads, gel bottle tips and gel had variable levels of contamination. Tips of gel bottles had the highest contamination, with 52.7% positive for non-specific bacterial contamination and 3.6% positive for methicillin-resistant Staphylococcus aureus (MRSA). Contamination of gel by non-specific bacteria was found in 14.5% of bottles sampled. US heads (35.5% of those sampled) had non-specific bacterial contamination, with no MRSA detected. Disinfecting US heads after initial swabbing resulted in removal of 90.9% of non-specific contamination. Gel storage at temperatures below 40 °C was found to encourage the growth of mesophilic bacteria. This study demonstrates the need for better cleaning and storage protocols for US heads and gel bottles in PT clinics.

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

PURPOSE: Hospital-acquired infections is a major concern affecting patient management, in which medical instruments and devices play an important role. The purpose of this study was to determine the degree of bacterial contamination of the sonographic probe and describe an effective, safe, and practical decontamination method. METHODS: The study's sample consisted of 50 patients. Cultures were taken from the probe surface both after each examination and after the probes had been wiped clean with a dry, nonsterile paper towel. Cultures were also taken randomly from the coupling gel. RESULTS: Initial cultures were positive in 49 cases (98%) for aerobic and in 26 cases (52%) for anaerobic bacteria. Cultures obtained after cleaning the probe were positive in only 21 cases (42%) for aerobic and in 12 cases (24%) for anaerobic bacteria. The most common bacteria isolated in the aerobic cultures were Streptococcus aureus and Staphylococcus epidermidis, and in the anaerobic cultures were Peptococcus spp. and Peptostreptococcus spp. All cultures taken from the coupling gel were negative. CONCLUSIONS: Sonographic probes may act as a medium for bacterial contamination and transmission. Cleaning of the probe with a dry, nonsterile paper towel is an easy, effective, low-cost, and device-friendly method that can reduce this risk.

Hospital-wide survey of bacterial contamination of point-of-care ultrasound probes and coupling gel.

OBJECTIVES: The purpose of this study was to determine the hospital-wide incidence of bacterial contamination of point-of-care (bedside) ultrasound probes and coupling gel at a single academic medical center to predict the risk of nosocomial spread of infection. METHODS: Bacterial cultures were performed on all point-of-care ultrasound probe surfaces and associated gel bottles in our institution (82 total probes in 9 separate departments). This process was repeated every 2 weeks for a total of 8 weeks; therefore, each probe was cultured 4 times during the study period. RESULTS: Of the 320 probe cultures, 18 (5.6%), resulted in positive growth, all of which identified nonpathogenic organisms common to human skin flora and the environment. No methicillin-resistant Staphylococcus aureus or other notable pathogens were identified. No gel cultures resulted in bacterial growth. CONCLUSIONS: Bacterial contamination of point-of-care ultrasound probes and coupling gel is low at this single academic medical center and involves nonpathogenic organisms only.

Ultrasound probes as a possible vector of bacterial transmission.

Ultrasound probes are usually in a direct contact with the skin when used for detecting pathologic abnormalities. The probe could be a vector of bacterial transmission, but there have been few studies on this topic.We have made such studies, briefly reviewing 1)the conditions governing a possible bacterial transmission by probe, 2) the deterioration of an ultrasound probe by alcohol disinfection, 3) a suitable method for evaluating bacterial contamination of an ultrasound probe, and 4) the best procedure for decontaminating such probes. This paper ,may lead to a formal consideration of the relationship between ultrasound probes and their roles in bacterial transmission in clinical practice.

High level disinfection of a home care device; to boil or not to boil?

We developed a percutaneous electrical transducer for home therapy of chronic pain, a device that requires high level disinfection between uses. The utility of boiling water to provide high level disinfection was evaluated by inoculating transducer pads with potential skin pathogens (Staphylococcus aureus, Mycobacterium terrae, Pseudomonas aeruginosa, Candida albicans) and subjecting them to full immersion in water boiling at 4200 feet elevation (95 °C). Log10 reductions in colony-forming units (cfu) at 10 min were 7.1, >6.3 and >5.5 for S. aureus, P. aeruginosa and C. albicans, respectively, but only 4.6 for M. terrae. At 15 min the reductions had increased to 7.5, >6.8, >6.6 and >7.5 cfu, respectively.

The presence of fungi on contact electrical stimulation electrodes and ultrasound transducers in physiotherapy clinics.

OBJECTIVES: To evaluate the presence of fungi on contact electrodes and ultrasound transducers from physiotherapy clinics. DESIGN: Quantitative study conducted at the Laboratory of Microbiology and Immunology, Faculty of Health Sciences and Technology of Piauí - NOVAFAPI, Teresina, Brazil. SETTING: Sample collection was performed in 10 clinics (20 ultrasound transducers and 20 contact electrodes). MAIN OUTCOME MEASURES: Swabs were soaked with saline solution, inoculated in culture and incubated for filamentous fungi and yeast growth. RESULTS: Fourteen taxons were identified: Acremomium hyalinulum (Sacc.), Aspergillus terreus, Candida albicans, Cladosporium cladosporioides, Cladosporium elatum, Cladosporium oxysporum, Cladosporium sphaerospermum, Cladosphialophora bantiana, Curvularia clavata, Curvularia senegalensis, Fusarium oxysporum, Penicillium decumbens, Scopulariopsis candida and Sporothrix schenckii. Aspergillus terreus, Cladosporium oxysporum, Sporothrix shenckii and Candida albicans were found most often on contact electrodes, and Penicillium decumbens and Cladosporium cladosporioides were found most often on ultrasound transducers. CONCLUSION: Fungi were found on all of the contact electrodes and ultrasound transducers. Physiotherapy professionals need to improve the disinfection procedures for this equipment.

Evaluation of a new disinfection method for ultrasound probes used for regional anesthesia: ultraviolet C light.

OBJECTIVES: Ultrasound-guided regional anesthesia is commonly used for block placement. At present, the risk of cross contamination from probes is not well documented. To avoid transmission of infectious agents, several methods have been used for probe disinfection and protection. The aim of this study was to evaluate the antibacterial efficacy of a new high-level disinfection method based on ultraviolet C (UV-C) light under routine conditions after block placement with an unprotected probe. METHODS: The study was after approval by the local Ethics Committee. In the first part of the study, 15 ultrasound probes were exposed to a large inoculum of 3 bacteria. Ultraviolet C disinfection consisted of cleaning the probe with dry and disinfectant-impregnated paper followed by a 90-second UV-C disinfection cycle in a decontamination chamber. A protocol was established to retrieve the probe with sterile gloves after opening the door of the chamber. In the second part, 50 blocks were placed with ultrasound-guided regional anesthesia. The skin was first prepared with an antiseptic solution, and sterile gel was applied; no covers were used to protect the probes. The blocks were then disinfected with UV-C light. Bacteriologic samples were collected before and after the UV-C method and inoculated on chocolate agar plates. RESULTS: During the first part of the study, all probes were infected after inoculation (>150 colony-forming units) but were considered sterile (<10 colony-forming units) after disinfection. During the second part of the study, all probes were considered sterile before and after disinfection. CONCLUSIONS: Ultraviolet C disinfection seems relevant for ultrasound-guided regional anesthesia just before block placement. It offers simple, fast, and effective high-level disinfection. Moreover, this method should obviate the use of sterile probe covers, which can improve echogenicity.

Evaluation of ultraviolet C for disinfection of endocavitary ultrasound transducers persistently contaminated despite probe covers.

OBJECTIVE: To determine the rate of bacterial and viral contamination of endocavitary ultrasound probes after endorectal or endovaginal examination with the use of probe covers and to evaluate the antimicrobial efficacy of a disinfection procedure consisting of cleaning with a disinfectant-impregnated towel followed by disinfection with ultraviolet C (UVC) light. METHODS: Endovaginal or endorectal ultrasound examinations were performed for 440 patients in 3 institutions. All probes were covered by a condom or sheath during the examination. For bacterial analysis, 1 swab was applied lengthwise across one-half the surface of the probe just after removal of the probe cover. The second swab was similarly applied over the probe immediately after the end of a 2-step process consisting of cleaning with a towel impregnated with a disinfectant spray and a 5-minute UVC disinfection cycle. Swabs were applied onto plates and incubated for 48 hours. The number of colony-forming units was counted, and organisms were identified. A similar protocol was used for viral detection of Epstein-Barr virus, human cytomegalovirus, and human papillomavirus, except that an additional swab was applied along the entire external surface of the probe cover before its removal. Viruses were detected by means of a polymerase chain reaction-based protocol. RESULTS: After removal of probe covers, contamination by pathogenic bacteria was found for 15 (3.4% [95% confidence interval, 2.0%-5.6%]) of 440 probes, and viral genome was detected on 5 (1.5% [95% confidence interval, 0.5%-3.5%]) of 336 probes. After cleaning with a towel impregnated with a disinfectant spray and disinfecting with UVC light, neither bacterial pathogenic flora nor viral genome was recovered from the probe. CONCLUSIONS: Endocavitary ultrasound probes may carry pathogens after removal of covers under routine conditions. A disinfection procedure consisting of cleaning with a disinfectant-impregnated towel followed by disinfection with UVC may provide a useful method for disinfecting endocavitary ultrasound probes.

Are therapeutic ultrasound units a potential vector for nosocomial infection?

BACKGROUND AND PURPOSE: 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, therapeutic ultrasound has the potential to be a vector of infection in the physiotherapy setting. The purpose of the present study was to determine the degree of contamination on therapeutic ultrasound transducer heads and ultrasound gel after routine clinical use, and to evaluate the efficacy of recommended infection control procedures. METHOD: The study consisted of two phases. Using a prospective cross-sectional design, microbiological cultures were obtained from 44 transducer heads and 43 gels. Subjects were drawn from a variety of physiotherapy practice settings. All samples containing more than five colony forming units per cm2 were considered contaminated. Following these measurements, a repeated-measures design was used to re-evaluate the 44 transducer heads for the amount and type of bacteria present after cleaning with a 70% alcohol wipe. RESULTS: Twenty-seven per cent of transducer heads and 28% of gels were contaminated. Transducer heads showed fairly low levels of contamination across the sample, with the majority of organisms isolated found in normal skin and environmental flora. Gels were heavily contaminated with opportunistic and potentially pathogenic organisms, including Stenotrophomonas maltophilia, Staphylococcus aureus, Acinetobacter baumannii and Rhodotorula mucilaginosa. No multi-resistant organisms were identified. Cleaning with 70% alcohol significantly reduced the level of contamination on transducer heads (p < 0.01). CONCLUSIONS: Therapeutic ultrasound equipment is a potential vector for nosocomial infection in physiotherapy patients. The risk of infection from transducer heads can be effectively removed by cleaning with 70% alcohol between patients. Further research into possible strategies to reduce the risk of infection from ultrasound gels is needed.

Situação microbiológica dos transdutores piezoelétricos ultra-sônicos terapêuticos nos serviços de fisioterapia da Baixada Fluminense, Rio de Janeiro, Brasil / Microbiological situation of piezoeletric transducers therapeutical ultra sound at physiotherapy's service of Baixada Fluminense, Rio de Janeiro, Brasil

A terapia ultra-sônica caracteriza-se por ondas sonoras de alfa freqüência. O ultrasom subdivide-se em duas partes, o transdutor piezoelétrico e a corrente elétrica, sendo o último responsável por realizar a conversão de energia bruta em corrente elétrica alternada constante, que é transpassada pelo transdutor ao paciente. A técnica de aplicação do estímulo ultra-sônico expõe o transdutor em contato com o tecido afetado a ser tratado. Este fato identifica o equipamento e sua técnica de aplicações como possíveis veiculadores de bioagentes patogênicos. Os transdutores piezoelétricos ultrassônicos, de tamanho e marcas diversificadas, utilizados em pacientes foram submetidos à fricção circular com suabe embebido em soluções salina na área efetiva de radiação. No tempo de duas horas após a coleta foram semeados em meio de cultura de Brewer e Sabouraud. O crescimento obtido foi repicado para meios Agar-sangue, Agar-hipertônico-manitol e meio seletivo para gêneros Pseudomonas e Staphylococcus. A identificação foi feita por caracteres culturais e provas bioquímicas – Sistema BioMerieux Vitek. O crescimento fúngico foi identificado por caracteres morfológicos, culturais, provas bioquímicas e sorológicas, quando necessárias. Os resultados apontaram 65% de positividade nas amostras avaliadas com presença de agentes fúngicos e bacetrianos. A maior freqüência coube aos elementos fúngicos (40%) seguido de bacterianos (25%). Sugere-se necessidade de prevenção de transmissão de bioagentes por contato e melhora na qualidade do atendimento em fisioterapia.