Persistence of Microbial Contamination on Transvaginal Ultrasound Probes despite Low-Level Disinfection Procedure

Abstract

Aim of the StudyIn many countries, Low Level Disinfection (LLD) of covered transvaginal ultrasound probes is recommended between patients' examinations. The aim of this study was to evaluate the antimicrobial efficacy of LLD under routine conditions on a range of microorganisms.Materials and MethodsSamples were taken over a six month period in a private French Radiology Center. 300 specimens derived from endovaginal ultrasound probes were analyzed after disinfection of the probe with wipes impregnated with a quaternary ammonium compound and chlorhexidine. Human papillomavirus (HPV) was sought in the first set of s100 samples, Chlamydia trachomatis and mycoplasmas were searched in the second set of 100 samples, bacteria and fungi in the third 100 set samples. HPV, C. trachomatis and mycoplasmas were detected by PCR amplification. PCR positive samples were subjected to a nuclease treatment before an additional PCR assay to assess the likely viable microorganisms. Bacteria and fungi were investigated by conventional methods.ResultsA substantial persistence of microorganisms was observed on the disinfected probes: HPV DNA was found on 13% of the samples and 7% in nuclease-resistant form. C. trachomatis DNA was detected on 20% of the probes by primary PCR but only 2% after nuclease treatment, while mycoplasma DNA was amplified in 8% and 4%, respectively. Commensal and/or environmental bacterial flora was present on 86% of the probes, occasionally in mixed culture, and at various levels (10->3000 CFU/probe); Staphylococcus aureus was cultured from 4% of the probes (10-560 CFU/probe). No fungi were isolated.ConclusionOur findings raise concerns about the efficacy of impregnated towels as a sole mean for disinfection of ultrasound probes. Although the ultrasound probes are used with disposable covers, our results highlight the potential risk of cross contamination between patients during ultrasound examination and emphasize the need for reviewing the disinfection procedure.

A risk for non-sexual transmission of human papillomavirus?

“…Similarly, HPV was detected in six pre-examination samples. This study, as well as others, showed that a large amount of ultrasound probes were contaminated with high-risk HPV [57][58][59][60]. As discussed, most clinical disinfectants are inadequate to neutralize HPV.…”

“…As discussed, most clinical disinfectants are inadequate to neutralize HPV. Other studies looked at transvaginal ultrasound probes further and concluded that not only are they contaminated by HPV DNA, but also by free virions [59]. They determined this by treating swab samples with an exonuclease, which destroys all unprotected DNA.…”

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

“…Ethyl and propyl alcohol are effective decontaminants with success rates as high as 100 % [9] however, may damage the transducer, therefore Koibuchi et al [10] has suggested wiping the probes with a plain paper towel after every ultrasound examination, although to a degree that is not comparable with that obtained by using an alcohol-soaked paper towel. The other suggestion is wiping the probe with an alcoholsoaked paper towel before examination for patients with immunosuppression disease or after the examination of a patient with a skin infection, and at the end of each working day, additionally, the probe should be wiped with an alcohol-soaked paper towel [11].…”

Guidelines for Reprocessing Ultrasound Transducers

“…This reduces the risk of potential crosscontamination between the patients and the operator. 22,[26][27][28][29] Ensure that all cleaning agents used for the general environment have been approved by the equipment manufacturer.…”

“…Several studies have examined the likelihood of transmission of this organism through transvaginal ultrasound using current infection control practices and found that transducer covers do not adequately prevent the contamination of transducers with HPVs 24 and that low-level disinfection may not remove HPV from ultrasound transducers. 22,24 Many other potentially infectious agents may be transmitted via improperly maintained, cleaned and disinfected ultrasound equipment, accessories and transducers, including protozoal pathogens such as Trichomonas vaginalis, intestinal parasites such as Entamoeba histolytica or fungal pathogens including dermatophytes and hyphomycetes.…”