Introduction

Today, electronic devices, such as mobile phones and computers have become an integral part of our lives, the use of which in different environments is rapidly growing, and teaching hospitals and clinics are no exception (1). Computers are used extensively in healthcare settings as they provide assistance in different aspects of diagnosis and treatment. In addition, mobile phones are widely used because they are fast and efficient.

Mobile phones are carried all day long and must be cleaned properly since people may not wash their hands as often as they should (2). It has been demonstrated that frequent contact with mobile phones exposes individuals to normal flora of skin (3, 4). Moreover, computer mice and keyboards, especially in multi-user ones, are highly contaminated and need proper disinfection (3, 5, and 6). This contamination is a more serious hazard in healthcare environments
(1, 7-10).

It seems that mobile phones, as well as computer mice and keyboards of healthcare workers act as a reservoir of nosocomial pathogens and can potentially contribute to cross-contamination, especially if effective disinfection protocols are not applied (11-19). Ramesh et al. reported that more than half of the studied healthcare workers have never cleaned their phones (20). It has also been indicated that 5-81% of healthcare workers’ mobile phones are contaminated with nosocomial microorganisms (2, 19, 21-25).

Degree of contamination of mobile phones and computers of dental clinics has not been exactly confirmed and research in this regard is very limited since there are no well-defined cleaning guidelines available for electronic devices in dental environments. With this background in mind, this study aimed to evaluate the rate and typing of contamination by microorganisms found on mobile phones and computer mice and keyboards used in dental and non-medical schools.

Materials and Methods

The research was confirmed by the Research Deputy of Mashhad University of Medical Sciences, Mashhad, Iran. This cross-sectional study was conducted to evaluate the microbial contamination of electronic devices, including computers and mobile phones, in two academic schools in 2015. Samples of the dental school were as the test group, while the control group consisted of samples of the non-medical school. Sample size was 44 computers and 45 mobile phones in each group. The only inclusion criterion was the electronic device having been used for at least three months.

All the selected mobile phones had touch-screen technology and belonged to the students of academic schools. The computers in the test group were randomly selected from the computer center of the dental school and those of the dental clinic. Meanwhile, the computers in the control group were selected from the computer center of the non-medical school. All the computers in both groups were multi-user, whereas mobile phones were personal. Microbial swabs were collected from the center of the touch-screen of mobile phones, the Enter and Backspace keys of computer keyboards and from the left-click button of computer mice. Surface sampling was performed using a sterile adhesive tape, which was 1 cm in length and attached to the specified surface for one minute. Afterwards, the tape was removed and placed on a Blood Agar medium. After one minute, the tape was removed and the medium was immediately transferred to the microbiology laboratory of an academic hospital for microbial culture. Samples were cultured on blood and chocolate agar plates, which were incubated for 48 hours at 37 °C in 5 % CO₂. Plates which showed no growth were reported as negative, while those showing any growth were reported as positive. Positive growths were subsequently identified using routine microbiological methods. Initially, the morphology of colonies was evaluated and Gram staining was performed. In addition, further microscopic and biochemical tests such as coagulase, oxidase, catalase, bacitracin and optochin, were conducted to identify the type of microorganism. Gram-negative bacteria were cultured in Kligler Iron Agar for further confirmation, followed by enumeration of colony counts.

Total bacterial count was determined by visual counting and then the count was multiplied by 20 to express as colony forming units (CFU)/ml. Finally, the results of microbial culture were reported as units/ml.

Statistical analysis

Statistical analysis was performed in SPSS, version 15, using Kolmogorov-Smirnov (to confirm nonparametric distribution of the data) and Mann-Whitney U test (for pairwise comparison of the differences between the study groups). P-value less than 0.05 was considered statistically significant.

Results

According Kolmogorov-Smirnov Test, normal distribution hypothesis of data was rejected ((P- values were less than 0. 5), so nonparametric tests were used.

Computer results

In this study, all the evaluated computers were multi-user. In the test group, computers were cleaned weekly by window cleaner (70.5%), damp cloth (4.5%), and Deconex solution (4.5%) or they were not cleaned (20.5%) at all. In the control group, the cleaning process was performed every two or three weeks using a damp cloth. Mean durations of computer use were 1.6 and 5.6 hours/day in the test and control groups, respectively.

Computers of the test group were divided into clinical (81.8%) and non-clinical (18.2%) subgroups. Fungal contamination of the clinical computers was significantly higher than the non-clinical ones (P=0.01). Contaminations of the two subgroups of computers of the test group were not significantly different.

Microorganism culture results of computer samples are provided in Table 1. The most common microorganism in the study group was Staphylococcus epidermidis, found in 82% of the samples. While Staphylococcus aureus was detected in 3.8% of computers of the test group, this bacterium was not observed in the control group, which was indicative of a statistically significant difference (P=0.02). Moreover, Micrococcus contamination was significantly more observed in the test group (P<0.001). In the control group, a significantly higher contamination with Bacillus, Enterococcus, Corynebacterium, Tetragenococcus, and fungi was observed, compared to the test group (Table 1). In terms of computer contamination, keyboards were significantly more contaminated, compared to computer mice (P=0.004) (Table 2).

Mobile phone results

Overall, 60% of the mobile phones in the test and 62.2% in the control group were cleaned by dry cloth. Other mobile phones were cleaned by damped cloth with alcohol or Deconex solution, window cleaner, finger alone, or were not cleaned at all. Mean durations of mobile phone use were 4.17 and 3.08 (h/day) in the test and control groups, respectively.

Microorganism culture results of the mobile phone samples are presented in Table 3. According to the results presented in this table, no positive culture results were observed in 13.3% and 11.1% of the mobile phones in the test and control groups, respectively. The most common microorganisms in the test group were Bacillus (57.8%) and Staphylococcus epidermidis (42%), while they were Staphylococcus epidermidis (66.7%) and Bacillus (40%) in the control group. Although contamination with Bacillus was significantly more common in mobile phones of the test group (P=0.02), Staphylococcus epidermidis and Corynebacterium contamination was significantly more prevalent in mobile phones of the control group, P=0.03 and P=0.04, respectively (Table 3).

 Table 1. Microorganisms isolated from computers and comparison the test (dental) and control (non-medical) groups

¹Number of contaminated samples

²Percentage of contaminated samples

Table 2. Comparison microbial contamination of computer mice and keyboards

^a Enter & Backspace keys, ^b Mean level of contamination (Mean CFU)

Table 3. Microorganisms isolated from mobile phones and comparison the test (dental) and control
 (non-medical) groups