Study design, area, and period

A cross-sectional study was conducted on health professionals’ mobile phones working at Hiwot Fana Specialized University Hospital, Harar, Eastern Ethiopia, from February to March 15, 2018. Harar is located 526 km away from Addis Ababa, the capital city of Ethiopia. There are six hospitals (4 governments and 2 private hospitals), 8 health centers, and 26 health posts in the region. Hiwot Fana Specialized University Hospital (HFSUH) is one of the referral teaching hospitals in Ethiopia. Currently, the hospital provides health care service to more than five million peoples around Harar and neighboring regions like Oromiya Regional State, Dire Dawa Administrative Council, and Ethiopian Somali Regional State. The hospital has 787 workers in which 371 of these workers are health professionals.

Sample size and sampling techniques

The sample size was determined by a single population proportion formula using the prevalence of bacterial contamination from a study conducted in Hospital of the University of Gondar (0.98) [6], with a margin of error of 0.03 and Z score for 95% confidence interval of 1.96, and finally, a 15% non-response rate was added. The final sample size was 240. This sample size was allocated proportionally to the number of health professionals in the hospital. Then, a simple random sampling technique was used to select the mobile phones of individual health care professionals (Fig. 1).

Fig. 1 Schematic presentation of the sampling technique. N.B.: N = the total population size, Ni = population size of each occupation, ni = sample size drawn from each occupation/profession, n = sample size required Full size image

Data collection methods

Data were collected using

Interview

Data were collected by a self-administered questionnaire after oral and written consent obtained from health professionals. The questionnaire was developed from different literature [6, 16, 17] which has two parts. Socio-demographic variables like age, sex, and educational level were the first part, while the second part includes mobile phone-related questions like the type of mobile phone, cleaning habit of a mobile phone, duration of mobile phone use, and the location for mobile use.

A swab of mobile phone for microbial culture and identification

After completion of self-administered questionnaires, a swab sample was collected from the participant’s mobile phone. Before taking a swab, both hands of laboratory technicians were cleaned using an alcohol-based instant hand sanitizer, and powder-free disposable gloves were worn per sample throughout the work to prevent cross-contamination. Sterilized cotton swab moisten by sterile normal saline was rotated to swipe from overall (screen, keypad, sides, and back) area of the mobile phone. In the case of mobile phones with covers, the swab was taken from the outer surfaces of the cover, besides the screen [16]. Then, the mobile phone swab was placed immediately into sterile normal saline in a sterile container and transported to the Microbiology Laboratory, Department of Medical Laboratory Sciences at Haramaya University, within 30 min for microbiological analysis as described by Shooriabi et al. [18].

The collected samples were inoculated onto Blood Agar and MacConkey Agar (Oxoid, LTD, UK) by following the standard streak plate technique [19]. The inoculated plates were incubated aerobically at 37 °C for 24–48 h. Primary isolation of bacteria was made based on their colony characteristics and Gram stain reaction microscopically. Different biochemical tests like triple sugar iron agar, indole, citrate, oxidase, urease, motility, Voges–Proskauer, methyl red, mannitol, catalase, and coagulase were used for further identification.

Antimicrobial susceptibility test

Antimicrobial susceptibility test was done according to the Clinical Laboratory Standards Institute guidelines [20] using the Kirby-Bauer disc diffusion method. In brief, the pure isolate (four to five colonies) was added to a sterile tube containing 5 ml of normal saline and mixed gently until it forms a homogeneous suspension. The turbidity of bacterial suspension was standardized by using 0.5 McFarland standards. A sterile cotton swab was dipped into the suspension and inoculated the bacterial suspension over the entire surface of Mueller Hinton agar (Oxoid Ltd., UK) and left at room temperature to dry for 3 to 5 min. Then, antimicrobial drug discs were placed by using a disc dispenser on to the Muller Hinton agar and incubated at 37 °C for 18–24 h. At the end of the incubation period, the diameter zone of inhibition was measured by using a digital caliper. The growth inhibition zone was interpreted as susceptible, intermediate, or resistant after comparison with standard guidelines [20].

Operational definitions

Hand hygiene is a term used to cover both hand washing using soap and water, and cleaning hands with waterless or alcohol-based hand sanitizers.

Keypad mobile phone is a mobile phone with the screen installed separately on a push-button phone device for dialing a number.

Touchscreen mobile phone is a mobile phone display screen that acts as an input device.

Data quality assurance

The self-administered questionnaire was pretested on 5% of the sample size at Jugol General Hospital. The study participating health professionals were briefly instructed how to fill out the questionnaire. Training on how to collect swab samples was given to data collectors. Completeness of each questionnaire was checked daily during the data collection period. All culture media were prepared by following the manufacturer’s instructions, and sterility was checked by incubating 5% of the prepared culture media at 37 °C overnight and checked for growth of contaminants. The reference strains Staphylococcus aureus (ATCC-25923) and Escherichia coli (ATCC-25922) were used to check the quality of culture media and antimicrobial discs. Double data entry was done using EpiData to minimize errors during data entry.

Data analysis

Data were entered into EpiData version 3.1, cleaned, and exported to Statistical Package for Social Sciences (SPSS) program version 20 for further cleaning and analysis. Descriptive statistics like mean, frequency, and percentage were performed on different variables. The magnitude of mobile bacterial contamination was determined as the proportion of those mobile phone samples reported having bacterial isolates by culture test. Bivariate and multivariate logistic regression was performed to identify factors associated with bacterial contamination. A variable with p value ≤ 0.25 in the bivariate analysis was a candidate for the multivariate logistic regression in multivariate analysis. The variables with a p value < 0.05 were considered statistically significant.