High level bacterial contamination of secondary school students' mobile phones

TiO2-Ag-NP adhesive photocatalytic films able to disinfect living indoor spaces with a straightforward approach

TiO₂-Ag doped nanoparticulate (TiO₂-Ag-NP) adhesive photocatalytic films were used to assess the ability in dropping down the burden of indoor microbial particles. The application of an easy-to use photocatalytic adhesive film to cleanse indoor living spaces from microbial pollution, represents a novelty in the field of photocatalytic devices. Reduction was attained by photocatalysis in selected spaces, usually with overcrowding (≥ 3 individuals) in the common working daily hours, and upon indoor microclimate monitoring. TiO₂-Ag doped nanoparticulate (TiO₂-Ag-NP) adhesive photocatalytic films were applied within five types of living spaces, including schools and job places. The microbial pollution was assessed at time 0 (far from routine clean, ≥ 9 h) and throughout 2-4 weeks following the photocatalyst application by relative light unit (RLU) luminometry and microbial indirect assessment (colony forming units per cubic meter, CFU/m³). TiO₂-Ag-NP photocatalyst reduced RLU and CFU/m³ by rates higher than 70% leading to RLU ≤ 20 and microbial presence ≤ 35 CFU/m³. The described TiO₂-Ag-NP is able to reduce microbial pollution to the lowest RLU threshold (≤ 20) within 60 min in open daylight in a standardized test room of 100 m². The correlation between RLU and CFU/m³ was positive (r = 0.5545, p < 0.05), assessing that the microbial reduction of indoor areas by the TiO₂-Ag-NP adhesive film was real. Titania photocatalysts represent promising tools to ensure air cleaning and sanitization in living indoor microclimates with a low cost, feasible and straightforward approach. This approach represents an easy to handle, cost effective, feasible and efficacious approach to reduce microbial pollution in indoor spaces, by simply attaching a TiO₂-Ag-NP adhesive film on the wall.

Smartphones as an Ecological Niche of Microorganisms: Microbial Activities, Assembly, and Opportunistic Pathogens

Smartphone usage and contact frequency are unprecedentedly high in this era, and they affect humans mentally and physically. However, the characteristics of the microorganisms associated with smartphones and smartphone hygiene habits remain unclear. In this study, using various culture-independent techniques, including high-throughput sequencing, real-time quantitative PCR (RT-qPCR), the ATP bioluminescence system, and electron microscopy, we investigated the structure, assembly, quantity, and dynamic metabolic activity of the bacterial community on smartphone surfaces and the user's dominant and nondominant hands. We found that smartphone microbiotas are more similar to the nondominant hand microbiotas than the dominant hand microbiotas and show significantly decreased phylogenetic diversity and stronger deterministic processes than the hand microbiota. Significant interindividual microbiota differences were observed, contributing to an average owner identification accuracy of 70.6% using smartphone microbiota. Furthermore, it is estimated that approximately 1.75 × 106 bacteria (2.24 × 104/cm2) exist on the touchscreen of a single smartphone, and microbial activities remain stable for at least 48 h. Scanning electron microscopy detected large fragments harboring microorganisms, suggesting that smartphone microbiotas live on the secreta or other substances, e.g., human cell debris and food debris. Fortunately, simple smartphone cleaning/hygiene could significantly reduce the bacterial load. Taken together, our results demonstrate that smartphone surfaces not only are a reservoir of microbes but also provide an ecological niche in which microbiotas, particularly opportunistic pathogens, can survive, be active, and even grow. IMPORTANCE Currently, people spend an average of 4.2 h per day on their smartphones. Due to the COVID-19 pandemic, this figure may still be increasing. The high frequency of smartphone usage may allow microbes, particularly pathogens, to attach to-and even survive on-phone surfaces, potentially causing adverse effects on humans. We employed various culture-independent techniques in this study to evaluate the microbiological features and hygiene of smartphones, including community assembly, bacterial load, and activity. Our data showed that deterministic processes drive smartphone microbiota assembly and that approximately 1.75 × 106 bacteria exist on a single smartphone touchscreen, with activities being stable for at least 48 h. Fortunately, simple smartphone cleaning/hygiene could significantly reduce the bacterial load. This work expands our understanding of the microbial ecology of smartphone surfaces and might facilitate the development of electronic device cleaning/hygiene guidelines to support public health.

Germi-X herbal-based spray disinfects smartphone surfaces: implication on fomite-mediated infection spread

Inanimate objects/surfaces become fomites upon contacting infectious agents such as disease-causing bacteria, fungi and viruses. Smartphones are one of the most prominent among these fomites. COVID-19 pandemic has raised the awareness on mobile sanitization, as an active measure to curb fomite-mediated viral transmission. Available mobile sanitizers and ultraviolet (UV) ray mediated mobile sanitization have their own sets of pros and cons, often being less user-friendly. This study explored the germicidal efficacy of an herbal-based sanitizer, Germi-X spray, on hands and mobiles, through microbiological techniques of micro-broth dilution and Kirby-Bauer disc diffusion assay, thumb print assay and swab test. Notably, Germi-X spray was found to be 6–67% more effective against surface pathogens, like, Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas fluorescens and Pseudomonas aeruginosa, as compared to a very popular product in the Indian market, which was taken as a control for this study. The observed anti-bacterial activity of the spray from disc-diffusion assay suggests its greater surface retentivity as compared to the control. Germicidal potency of Germi-X spray, when used to sanitize hands, was found to be greater than 80%. There was ~ 17-fold reduction in microbial counts after sanitizing smartphones with Germi-X spray. The novelty of this study lies in providing experimental evidence for this herbal-based surface sanitizer in efficiently disinfecting one of the super contaminated fomite, the smartphones. In conclusion, having an herbal base with a high germicidal efficacy against surface pathogens, together with longer surface retention, Germi-X spray appears to be an eco-friendly and cost-effective sanitizer for the surfaces of electronic gadgets like smartphones.

Determination of drug-resistant bacteria in palmar surface and touchscreen cell phones from bystanders in an urban community

The dynamic microbiota of the human palmar surface (PS) is related to the various hygienic habits of humans and can be transmitted or exchanged upon contact with objects of daily use, such as the indispensable touchscreen cell phone (TCP); this interaction could allow the development of drug-resistant bacteria. The objective was to determine the drug-resistant bacterial contamination between PSs and TCPs in an urban community. Among the total bacterial colonies isolated and molecular and phylogenetically characterized based on the V4-V6 regions of the 16S rRNA gene from PSs and TCPs, the genera present in both types of samples were Staphylococcus (53.3 and 43.5 %, respectively), Bacillus (37.8, 37 %), Atlantibacter (2.2, 10.8 %) and Microbacterium (2.2, 4.3 %). The genera present in only one type of sample were Rothia, Paenibacillus, Escherichia and Micrococcus (2.2 % each). Resistance to penicillins (35.6-93.5 %) and nonsusceptibility to cephalosporins (8.9-37 %) and nitrofurantoin (13.3 and 15.2 %) were observed. The percentage of multidrug antibiotic resistance was 15.4 %. The prevalence of drug-resistant and multidrug-resistant bacteria in PSs and TCPs in the community could give rise to human health problems, and hygiene measures are recommended.

Review of microbial touchscreen contamination for the determination of reasonable ultraviolet disinfection doses

Background: Touchscreens are usually microbially contaminated and can therefore act as fomites inside and outside healthcare environments. Due to the increasing use of such touchscreens and the growing awareness of infection risks, approaches that allow safe and automatic disinfection are desired. Ultraviolet (UV) irradiation, with its known antimicrobial efficacy, could achieve this goal, but should be executed with limited touchscreen degradation, disinfection duration, and energy consumption. It should also pose as little harm as possible to humans even in case of failure. Materials and methods: A literature search was performed first to identify the microorganisms most commonly found on touchscreens. Then, the 90% reduction doses (D90 doses) for the different relevant microorganisms and UV spectral ranges were determined from the literature, and irradiation doses are suggested that should reduce most of these important microorganisms by 5 log-levels. Results: The most frequent microorganisms are staphylococci, bacilli, micrococci, enterococci, pseudomonads and E. coli with small differences between hospital and community environments, if antibiotic resistance properties are ignored. The determined irradiation doses for a 5 log-reduction of the most frequent microorganisms are about 40 mJ/cm2, 80 J/cm2, 500 J/cm2 and 50 mJ/cm2 for the UV spectral ranges UVC, UVB, UVA and far-UVC, respectively. These doses are also sufficient to inactivate all nosocomial ESKAPE pathogens on touchscreens by at least 99.999%. Conclusion: Disinfection is achievable in all UV spectral ranges, with UVC being the most effective, enabling automatic disinfection within a minute or less. The much higher doses required in the UVB and UVA spectral range result in much longer disinfection durations, with the advantage of a reduced risk to humans. For all kinds of UV irradiation, the doses should be limited to reasonable values to avoid irradiating an already more or less sterile surface and to prevent degradation of touchscreen devices.

Forensic Applications of Microbiomics: A Review

The rise of microbiomics and metagenomics has been driven by advances in genomic sequencing technology, improved microbial sampling methods, and fast-evolving approaches in bioinformatics. Humans are a host to diverse microbial communities in and on their bodies, which continuously interact with and alter the surrounding environments. Since information relating to these interactions can be extracted by analyzing human and environmental microbial profiles, they have the potential to be relevant to forensics. In this review, we analyzed over 100 papers describing forensic microbiome applications with emphasis on geolocation, personal identification, trace evidence, manner and cause of death, and inference of the postmortem interval (PMI). We found that although the field is in its infancy, utilizing microbiome and metagenome signatures has the potential to enhance the forensic toolkit. However, many of the studies suffer from limited sample sizes and model accuracies, and unrealistic environmental settings, leaving the full potential of microbiomics to forensics unexplored. It is unlikely that the information that can currently be elucidated from microbiomics can be used by law enforcement. Nonetheless, the research to overcome these challenges is ongoing, and it is foreseeable that microbiome-based evidence could contribute to forensic investigations in the future.

Isolation of Gram-Positive, Antibiotic-Resistant Bacteria from Tactile Mobile Phones in a Northwestern Mexican City

The widespread use of touch-screen mobile devices renders them potential fomites for the transmission of bacterial pathogens among users of different ages. The objectives of the present research were to isolate bacteria from mobile phones, perform molecular and phylogenetic identification, and determine the antibiotic resistance profiles. The surfaces of 50 touch-screen mobile devices owned by bystanders were sampled in the city center of Culiacan, Sinaloa, Mexico. The samples were cultured on nutritive agar; 13 bacterial colonies were isolated and characterized based on their macroscopic and microscopic characteristics and then identified using PCR amplification and sequencing of the 16S rRNA gene V4 and V6 regions. Their taxonomic relationships were determined via a Bayesian inference approach. Antimicrobial resistance was evaluated via disc diffusion and broth microdilution assays. Species of the genera Staphylococcus, Bacillus, and Enterococcus were identified on 84.6, 7.7, and 7.7% of the mobile phones, respectively. A unique subgroup of Staphylococcus epidermidis was identified in strains FBOPL-23, CAEPL-28, and FREPL-28. Staphylococcus hominis novobiosepticus was also identified on mobile phones for the first time. Of the isolated bacteria, 92.3% were resistant to erythromycin, 76.9% to ampicillin and penicillin, 61.5% to dicloxacillin, 38.5% to cephalothin and 7.7% to cefotaxime and ceftriaxone. The presence of antibiotic-resistant bacteria of clinical relevance poses potential risks to users' health and the dissemination of antibiotic resistance mechanisms throughout the community; thus, we recommend regular cleaning to prevent cross-infection by multidrug-resistant bacteria when using touch-screen mobile devices.

Surface touch and its network growth in a graduate student office

Fomites transmit infection. A key question is how surface contamination in a building is spread by human touch. Using video cameras, we collected more than 120 000 touch actions from 60 hours of high-resolution data on surface touch across five typical weekdays in a graduate student office. The students touched surfaces with one or both hands during 94.6% of the observed period. On average, each student made five touches per minute, with an average duration of 22 seconds per touch. High-touch and high-risk surfaces and people were identified. 98.8% of the surfaces touched, such as mobile phones and human faces, were private, but public surfaces, such as a water dispenser button, were touched by 68% of the students in the office on average. Compared with females, males spent 3% more time touching surfaces. Right hands always had higher touch frequency than left hands. The surface network in the office was scale-free, whereas the hand network was small-world. The results revealed power law and logistic growth in the number of contaminated surfaces which suggests that fomite transmission can be extremely effective. The time taken for most surfaces to be contaminated after one surface became contaminated was much shorter for public than for private surfaces.

Cultivable Microbial Diversity Associated With Cellular Phones

A substantial majority of global population owns cellular phones independently to demographic factors like age, economic status, and educational attainment. In this study, we investigated the diversity of microorganisms associated with cellular phones of 27 individuals using cultivation-based methods. Cellular phones were sampled using cotton swabs and a total of 554 isolates representing different morphotypes were obtained on four growth media. Matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry could generate protein profiles for 527 isolates and species-level identification was obtained for 415 isolates. A dendrogram was constructed based on the protein profiles of the remaining isolates, to group 112 isolates under 39 different proteotypes. The representative strains of each group were selected for 16S rRNA gene and ITS region sequencing based identification. Staphylococcus, Bacillus, Micrococcus, and Pseudomonas were the most frequently encountered bacteria, and Candida, Aspergillus, Aureobasidium, and Cryptococcus were in case of fungi. At species-level the prevalence of Micrococcus luteus, Staphylococcus hominis, Staphylococcus epidermidis, Staphylococcus arlettae, Bacillus subtilis, and Candida parapsilosis was observed, most of these species are commensal microorganisms of human skin. UPGMA dendrogram and PCoA biplot generated based on the microbial communities associated with all cellular phones exhibited build-up of specific communities on cellular phones and the prevalence of objectionable microorganisms in some of the cellular phones can be attributed to the poor hygiene and sanitary practices. The study also revealed the impact of MALDI-TOF MS spectral quality on the identification results. Overall MALDI-TOF appears a powerful tool for routine microbial identification and de-replication of microorganisms. Quality filtering of MALDI-TOF MS spectrum, development of better sample processing methods and enriching the spectral database will improve the role of MALDI-TOF MS in microbial identifications.