Gabriele Messina 1,*, Mattia Fattorini 2, Nicola Nante 1,2, Daniele Rosadini 2, Andrea Serafini 2, Marco Tani 3 and Gabriele Cevenini 4
- Laboratory of Environmental Hygiene, Department of Molecular and Developmental Medicine, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy; nicola.nante@unisi.it
- Post Graduate School of Public Health, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy; fattorini7@student.unisi.it (M.F.); daniele.rosadini@student.unisi.it (D.R.); serandre85@gmail.com (A.S.)
- FeT Elettronica S.n.c Via A. Volta 28, 53036 Poggibonsi (Siena), Italy; mtani@fet.it
- Department of Medical Biotechnologies, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy; gabriele.cevenini@unisi.it
- Correspondence: gabriele.messina@unisi.it; Tel.: +39-05-7723-4139; Fax: +39-05-7723-4465
Academic Editors: Daniela Haluza, Hanns Moshammer and Stana Simic
Received: 2 August 2016; Accepted: 15 September 2016; Published: 23 September 2016
Abstract: Today it is well demonstrated that stethoscopes can be as contaminated as hands, which are a recognized source of Health-Care Associated Infections (HCAIs). Ultraviolet C (UVC) light has proven disinfection capacity and the innovative UVC technology of Light Emitting Diode (LED) shows several potential benefits. To verify whether the use of UVC LEDs is effective and reliable in stethoscope membrane disinfection after prolonged use, a pre-post intervention study was conducted. A total of 1668 five-minute cycles were performed on two UVC LEDs to simulate their use; thereafter, their disinfection capacity was tested on stethoscope membranes used on a previously auscultated volunteer. Then, a further 1249 cycles were run and finally the LEDs were tested to assess performance in reducing experimental contamination by Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli on the stethoscope membrane. Baseline volunteer contamination identified 104 Colony Forming Units (CFUs) while treated Petri dishes had 12 and 15 CFUs (p < 0.001). Statistically significant differences (p < 0.001) were also found relating to the reduction of specific bacteria: in particular, after treatment no CFU were observed for S. aureus and E. coli. UVC LEDs demonstrated the capacity to maintain high levels of disinfection after more than 240 h of use and they were effective against common microorganisms that are causative agents of HCAIs.
Keywords: disinfection; ultraviolet; LED; stethoscope; health-care associated infections
1. Introduction
According to the World Health Organization (WHO), Health-Care Associated Infections (HCAIs) «[ . . . ]are infections that patients acquire while receiving treatment for medical or surgical conditions and are the most frequent adverse event during care delivery» [1]. Zimlichman et al. [2] evaluated that the five most common types of HCAIs (surgical site infections, central line-associated infections, catheter-associated infections, ventilator associated pneumonia and Clostridium difficile infections) have an annual economic impact of $9.8 billion in the U.S. It is also estimated that up to 32% of HCAIs can be prevented [3]. It is widely reported that environmental surfaces and medical devices make a substantial contribution to the transmission and diffusion of HCAIs in healthcare settings [4 7]. According toWeber et al. [5], 20%–40% of HCAIs could be caused by pathogens hosted on the hands of Health-Care Workers (HCWs), which may become contaminated after contact with inanimate surfaces.
Moreover, it has been reported that certain pathogens (e.g., Methicillin-resistant Staphylococcus aureus, Vancomycin-resistant Enterococcus and C. difficile) could even survive for a month on environmental surfaces and medical devices [5,8]. Although it is difficult to highlight a direct association between stethoscope contamination and the onset of HCAIs [3], microbial contamination of stethoscopes has already been demonstrated, and this may contribute in spreading of pathogens involved in HCAIs. In addition, it has also been demonstrated that the level of contamination is comparable to that of the physician’s dominant hand, one of the leading causes of HCAIs [3,9]. Studies have shown the presence of the same bacterial strain both in patients and on stethoscopes previously used for their auscultation [10,11]. Hence, stethoscope disinfection gains remarkable importance, although surveys show that up to 90% of physicians do not disinfect their stethoscope after performing examinations [9]. This poor compliance among HCWs could be explained by various factors, such as lack of prompt cleaning agents and high workload leading to forgetfulness but, if informed, HCWs do realize the importance of cleaning the stethoscope [12]. The use of Ultraviolet C light (UVC) emitted by Light Emitting Diodes (LEDs) has been already proposed and tested as a method for obtaining disinfection of the stethoscope membrane [13], but considering the early adoption of this technology and the shorter operative life of UVC LEDs than standard ones, to our knowledge, there is a lack of data concerning the effectiveness of LEDs after prolonged use. The aim of the study is to verify whether, after extended use, UVC LEDs remain effective in significantly reducing stethoscope membrane contamination both on the skin and in a laboratory setting.
2.1. Setting
An experimental design with pre-post treatment was conducted between August 2015 and March 2016 in the Laboratories of the Department of Molecular and Developmental Medicine, University of Siena. Using a 3D printer (Sketchup, Boulder, CO, USA) we created an experimental prototype for properly placing LEDs and the stethoscope head (Figure 1).
Figure 1. Experimental prototype developed for the execution of the experiments. On the right, the correct positioning of the stethoscope head during Ultraviolet C light (UVC) disinfection is shown.
Two UVC LEDs (LED 16 and 18) produced by SeoulViosys (Ansan-si, Gyeonggi-do, Korea),(model CUD8DF1A, 275 nm wavelength-peak, average power 2.4 mW) were used to irradiate a
stethoscope head inserted in the prototype, at a distance ranging from 11 to 23 mm, in the center and edges of the membrane respectively. Implementing a battery power supply and a microcontroller, we were able to run repeatable cycles using 5 min of irradiation followed by 1 min of inactivity. Each cycle of functioning corresponded to one disinfection procedure after stethoscope auscultation of a patient. The irradiation time of 5 min was chosen in accordance with previous laboratory tests based on several factors: UV LED power, distance from the LED and irradiation target, UV susceptibility of the different bacteria [14] and factors reducing UV effectiveness (sweat, sebum). Taking into account the more resistant bacteria among those most commonly found on the skin, a rough calculation of the time sufficient for a 2 log reduction of the bacterial contamination was approximately 2–3 min. Therefore, we chose a time of 5 min in order to overcome additional obstacles such as partial overlapping of bacteria, sebum, sweat, other biological fluids, etc. The whole study was conducted in rooms with air conditioning, at a mean air temperature of 23 C.
2.1. Setting
An experimental design with pre-post treatment was conducted between August 2015 and March 2016 in the Laboratories of the Department of Molecular and Developmental Medicine, University of Siena. Using a 3D printer (Sketchup, Boulder, CO, USA) we created an experimental prototype for properly placing LEDs and the stethoscope head (Figure 1).