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The plate count agar (PCA) culture plates showed bacteria growing from both the toilet seat and the smartphone sample. While many people think toilet seats are the dirtiest surfaces, smartphones may be dirtier than toilet seats, as shown in the figure where the colony number of a smartphone sample (174) is higher than that of a toilet seat (89). The presence of multiple colonies of varying sizes and morphologies indicates that smartphones can harbour diverse bacterial populations. These results highlight that smartphones can act as a source of bacterial contamination and may help spread germs through everyday contact.
After 24 hours of enrichment of the phone swab sample in tryptic soy broth (TSB), the culture was inoculated onto HiCrome MRSA agar. The left panel shows a negative sample, whereas the right panel shows a positive sample with presumptive MRSS colonies (green). HiCrome MRSA agar contains cefoxitin, which selectively inhibits methicillin-susceptible organisms, and chromogenic substrates that are metabolized by resistant staphylococci, resulting in the formation of green-pigmented colonies. A representative green colony was subsequently subcultured and subjected to Gram staining, which revealed Gram-positive cocci arranged in clusters, consistent with the characteristic microscopic morphology of staphylococci.
To evaluate the effect of cleaning a mobile phone with an alcohol swab (which was provided to all participants after sample collection), swab samples were collected from two halves of the same phone. One half was wiped with an alcohol swab prior to sampling, while the other half was left untreated.
For the HiCrome MRSA culture, the TSB-enriched sample obtained from the wiped side showed no growth, whereas the untreated side produced green-colored colonies suggestive of methicillin-resistant staphylococci (MRSS). This finding suggests that alcohol wiping may be effective in reducing or eliminating MRSS contamination on mobile phone surfaces.
For the total viable count assay, the wiped side yielded only 2 colonies, whereas the untreated side yielded 230 colonies on Plate Count Agar (PCA). This marked reduction in bacterial colony count demonstrates the effectiveness of alcohol wiping in reducing the overall microbial burden on the phone surface.
Although this observation was based on a single phone, the results highlight the potential benefit of routine alcohol-based disinfection in minimizing bacterial contamination of mobile devices.
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