Bacterial contamination of cellular phones at a Veterinary School and Veterinary Teaching Hospital

Introduction

Hospital-associated infections (HAIs) are a major concern in both human and veterinary medicine. While the actual prevalence of hospital-associated infections (HAI) in Veterinary hospitals is unknown, the Centre for Disease Control and Prevention in the USA reports that in 2011 there were over 700,000 human cases of HAIs in the USA (Lax and Gilbert, 2015). In the United Kingdom, it is estimated that there are over 10,000 deaths annually attributed to pathogens associated with HAIs (Pearson, 2009). While some HAIs may be transmitted directly from person to person, others may be transmitted via fomites such as staff clothing, stethoscopes, computer keyboards, and cellular phones.

The number of cellular phone users has been increasing exponentially and in 2014 there over 7 billion users (Yang et al., 2017). Cellular phones have now become an essential accessory to many persons and their use has infiltrated all aspects of our daily lives. Their value within the medical field is without doubt since they can provide quick and convenient access to reference material, laboratory results, and life-saving consultations in emergencies (Olsen et al., 2020). Such is their importance, that it can be assumed that almost every practitioner owns a cellular phone and a ban on their use in a clinical environment may be impractical (Imhoff, 2006). Given the intimate contact between cellular phones and their users it is not surprising that bacterial contamination of these devices have been reported to be as high as 100% (Srikanth et al., 2010, Tagoe et al., 2011). While the majority of the bacterial flora on these cellular phones may be non-pathogenic, some bacteria may contain virulence genes capable of causing disease or possess antimicrobial genes. Cellular phone users thus have to be wary of the potential for cellular phones acting as fomites in the dissemination of these organisms. This risk was highlighted by Ulger et al. (2009) who reported that 25%of cellular phones sampled from ICU staff were contaminated with Staphylococcus aureus, and 10% with coliforms (Ulger et al., 2009). Other studies have also identified foodborne pathogens amongst the microbial flora of cellular phones with Salmonella and Shigella spp. being among some of the bacterial isolates recovered. (Tagoe et al., 2011)

The increasing integration of cellular phone use in all facets of our lives potentially makes them an excellent mechanism for the dissemination of pathogens. Increasing use of cellular phones among medical personnel is of particular concern since these persons are exposed to a variety of situations which can result in their hands becoming contaminated with high concentrations of bacteria that can then transmitted onto their cellular phones. As such, the role of cellular phones as a fomite for the dissemination of pathogens warrants further investigation. From the literature cited above, it is clear the role of cellular phones in the dissemination of pathogens in human healthcare settings has been well described; however, this is not the case for Veterinary medicine and especially so for the Caribbean. This study seeks to partially fill this critical void by determining the frequency of contamination of cellular phones with Escherichia coli and coagulase-positive Staphylococcus aureus (CoPS) on cellular phones at a Veterinary School and Veterinary Teaching Hospital in Trinidad and Tobago as well as evaluate their cellular phone hygiene practices.            

Materials and methods

Sample collection and study population

A cross-sectional study was conducted targeting 120 veterinary students, technicians, and clinical faculty at a Veterinary School in Trinidad and Tobago. Using a stratified sampling method, participants from each category were approached and asked to participate in the study. Upon consenting to participate in the study, all surfaces of their cellular phone were aseptically swabbed using sterile gauze, moistened with sterile phosphate-buffered saline (Brady et al., 2011). The gauze was then placed in a Ziploc ® bag and kept in a cooler at 4^oC and transported back to the laboratory for microbial analysis within 4 hours.  The participant was also asked to complete a questionnaire which characterized their frequency of contact with animals as well as their cellular phone cleaning habits. 

Microbiological analysis

At the laboratory, the bags containing the sterile gauze were weighed on an electronic balance (Scout Pro SP202, Ohaus Corporation, USA) and sterile Buffered Peptone Water (Acumedia, MI) was added at a volume equivalent to nine times that of the sterile gauze. The contents of the bag were then manually agitated for two minutes to ensure adequate mixing of contents. The bags were then incubated for 24 hours are 37°C. Following incubation, one loopful, approximately 10 μL, of enriched broth solution was then streaked onto Mannitol Salt Agar, MSA, (Oxoid, UK) and Eosin Methylene Blue agar, EMB (Oxoid, UK) and incubated for 24 hours at 37°C.

The next day, MSA plates were examined for isolates with similar colony morphology to Staphylococcus aureus (yellow colonies) and these colonies were then subcultured onto 5% blood agar plates and incubated for 24 hours at 37°C for isolation. The next day, individual colonies were subjected to gram stain, coagulase, and catalase tests as described by Tallent et al. (Tallent et al., 2016). The EMB plates were also examined for blue-black colonies with a green metallic sheen and these suspected E. coli colonies were streaked onto 5% blood agar plates and incubated for 24 hours for isolation. The following day, the recovered isolates were then subjected to standard biochemical assays including Triple sugar iron, Simmons citrate, Urease, and Indole tests to confirm their identity as E. coli (Feng et al., 2002).

Statistical analysis

Data was tabulated using Microsoft Excel. Categorical associations were analysed using Fischer Exact Test and Chi-squared analysis. Differences were considered to be statistically significant at p < 0.05. Statistical analyses were done using SPSS® Statistics 22.0 (IBM®, Somer, NY, USA).

Results

Overall a total of 115 cellular phones were sampled, representing 95 students and 20 clinical faculty members of staff (Table 1). The study population was also categorised as being clinical or pre-clinical based on their progression in the academic programme. Students in year 5 and staff were classified as being clinical since they would have spent the majority of their time within the veterinary hospital or attending to ambulatory cases. Students enrolled in years 1 – 4 would have limited access to clinical settings and were thus classified as pre-clinical.

Cellular phone contamination: Of the 115 cellular phones sampled, only one cellular phone tested positive for Escherichia coli. In contrast, the frequency of contamination of phones with coagulase-positive Staphylococcus aureus (CoPS) was much higher, with 21% (24/115) testing positive for CoPS. The CoPS contamination on staff phones was higher than that of students (35% (7/20) vs 18% (17/95) but there was no statistical association between cellular phone contamination and whether the person was a student or staff (p = 0.16). (Table 2)

When categorised according to academic year enrolment, students enrolled in year 5 had the highestCoPScontamination rate with 40% (8/20) of phones being contaminated compared to the phones belonging to students enrolled in year 1 and year 2 who had the lowest (0%) (p < 0.001). Among the staff population, the contamination frequency among Veterinarian phones was higher than Veterinary Technicians (35.7% (5/14) vs. 33.3% (2/6), however, this difference was not statistically significant (p = 0.441).