Newly emerged-hygiene issue in the current lifestyles of wearing face masks during the COVID-19 pandemic

A recent article posted to the Research Square* preprint server and under consideration at Scientific Reports evaluated a novel hygiene concern that emerged during the coronavirus disease 2019 (COVID-19) pandemic, i.e., the adherence of fungi and bacteria to face masks. 

Background

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has prompted people to use face masks in public regularly. The three kinds of commercially marketed face masks are 1) cloth or gauze masks, 2) non-woven masks, and 3) polyurethane masks.

The World Health Organization (WHO) states that masks are only beneficial in combating COVID-19 when combined with non-pharmaceutical interventions such as hand hygiene. Moreover, the factors like correct mask use and disposal are also of paramount significance in curtailing the ongoing COVID-19 pandemic. 

While viruses cannot multiply without infecting host cells, most fungi and bacteria may exist and reproduce on various substrates (public transportation system, currency notes) depending on the circumstances. Despite substantial research into the efficiency of face masks in preventing SARS-CoV-2 transmission, there is no clarity on the possible hygiene difficulties caused by fungi and bacteria adhered to the mask surfaces. Furthermore, the hygiene of face masks during the COVID-19 pandemic is critical as the fungal and bacterial infections from the masks could aggravate COVID-19 infection.

About the study 

In the current work, the researchers demonstrated 1) the types and duration of mask use, 2) the number of fungi and bacteria adhering to the masks, and 3) the characterization of the fungi and bacteria sticking to masks. The team surveyed 109 medical students at Kindai University Faculty of Medicine, Japan, on their mask use during September and October 2020. The scientists assessed the association between microbes adhered to masks and factors associated with the subjects like gender, age, gargling habit, duration of mask use, natto consuming habit, and transportation. In addition, they also cultured bacteria and fungus on these volunteers' masks.

Before enrollment, informed consent was procured from all subjects, of which 63 were males, and 46 were females. The scientists ensured that none of the study participants were treated with antimicrobials during the research period. Microbes attached to the face masks were isolated by pressing the outer side and face side of the masks separately onto agar plates. These plates were then immediately covered to prevent contamination and then cultured. Subsequently, the fungal and bacterial colony counts were estimated.

Employing MiSeq, the 16S ribosomal ribonucleic acid (rRNA) sequencing was conducted. Fungi were identified by examining the colony microscopically and their morphology following lactophenol cotton blue staining. 

Findings and discussions

The results indicated that the bacteria colony counts were overall more than fungus colony counts on face masks. Further, fungal and bacterial colony counts were higher on the outer side and face side of the mask, respectively. The longer the mask was worn, the higher the fungal colony counts were, but this was not the case for bacterial colony counts. Non-woven masks harbored fewer fungi on the outside than other mask varieties. Despite the fact that bacterial colony counts were equivalent in all mask kinds, women had lower face-side counts than males.

According to the findings of the receiver operating characteristic (ROC) analysis, the Cladosporium genus, which was the most often identified fungus in this investigation, was discovered more frequently in females. B. subtilis was found more often on the masks of individuals who ate natto at least monthly. On the other hand, transportation systems were not linked to bacterial or fungal colony numbers. Of note, the ROC results were congruent with the study's findings. 

There were no significant variations in microbial colony counts across non-woven and other mask types when comparing the microbial colony counts based on mask type. The high fungal colony counts on the outer side of masks, according to these data, were linked to the length of mask use rather than the mask type. Immunocompromised individuals should be urged to use non-woven masks regularly, although the majority of the fungus found in this investigation were opportunistic pathogens. 

A foodborne pathogen named B. cereus was found on the outside of masks in 5% of the volunteers. This suggests that B. cereus may have gotten onto the masks through the hands from excrement. The authors advised intensive handwashing as it effectively lowered the occurrence of diarrhea.

Females who applied foundation on the left half of the face and wore face masks for four hours demonstrated no variation in bacterial colony counts across both sides of the face. Additionally, while facial skincare probably lowered bacteria on masks, it increased the presence of fungi. Similarly, those who used facial cleansers in the morning demonstrated lower bacterial counts but higher fungal counts.

Conclusions

The study findings implied that bacterial colony counts were higher on the face side of the masks than on the outer side. On the contrary, fungal colony numbers were lower on the face side than on the outer side of the masks. While the fungal colony counts were considerably higher after wearing the mask for extended periods, this was not the case for the bacterial colony counts. Although the majority of the detected microbes such as S. aureus, Cladosporium, and S. epidermidis were non-pathogenic, pathogenic microbes such as Microsporum, B. cereus, Aspergillus, and S. saprophyticus were also found.

Collectively, the present research indicates that individuals, particularly those with impaired immune systems, should avoid repeated usage of masks to forestall microbial infection. The present findings shed light on the usage of face masks to prevent potentially pathogenic infections during the SARS-CoV-2 pandemic.

*Important notice

Preprints with Research Square publish preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Written by

Shanet Susan Alex

Shanet Susan Alex, a medical writer, based in Kerala, India, is a Doctor of Pharmacy graduate from Kerala University of Health Sciences. Her academic background is in clinical pharmacy and research, and she is passionate about medical writing. Shanet has published papers in the International Journal of Medical Science and Current Research (IJMSCR), the International Journal of Pharmacy (IJP), and the International Journal of Medical Science and Applied Research (IJMSAR). Apart from work, she enjoys listening to music and watching movies.