During the COVID-19 pandemic, face masks have become a vital tool in limiting the transmission of the virus. Mask use is currently recommended by the Centers for Disease Control and Prevention, World Health Organization, and many local public health authorities. Although beneficial, face masks are associated with facial skin adverse reactions, including worsening of pre-existing dermatoses, pruritus, and abrasions.1,2 Patients use masks made from a variety of materials, all of which cover the lower and mid face. The significance of this alteration in the epithelial environment regarding the surgical site infection (SSI) is not known.
The primary objective of this study was to identify shifts in SSI rates and causative microorganisms after Mohs micrographic surgery (MMS) on mask-covered areas during the COVID pandemic compared with the pre-COVID era.
Methods
Design, Setting, and Participants
Patient data were collected by the retrospective chart review of all MMS cases performed by a single Mohs college fellowship–trained dermatologic surgeon at an academic medical center outpatient clinic. Data were obtained retrospectively, in an identical manner, from two 7-month time periods, with August 6, 2019, to March 21, 2020, representing the prefacial mask “control” period and May 6, 2020, to December 21, 2020, representing the COVID pandemic with universal facial mask wearing. May 6, 2020, was selected as the start date of the facial mask period because the academic hospital system and all affiliates instituted a universal mask requirement for all healthcare workers, patients, and visitors at that time.
Surgical site infection was defined as a diagnosis of wound infection by the surgeon in addition to the isolation of pathogenic organisms from the bacterial culture of the operative wound within the first 30 days after surgery. Facial masked sites were defined as the nose, nasolabial fold, cutaneous or mucosal lip, and chin. Cheek locations were not included because of variability in lateral facial coverage between different types of masks (Figure 1). The exclusion criteria for SSIs included cultures from wounds not related to MMS, repeat cultures on the same patient within the study period, repeat cultures from infections initially occurring before the study period, and cultures which grew normal skin flora.
Figure 1.
Facial locations included under the mask location definition highlighted in red. Cheek locations were not included because of variability in lateral facial coverage between the different types of masks. Created with BioRender.com.
Statistical Analysis
The study protocol was exempted by the Washington University Institutional Review Board. Differences between the two cohorts were compared using the chi-square and t-test. p < .05 was considered significant. Statistical analysis was performed using SPSS v26 (IBM, Armonk, NY).
Results
Eight hundred nineteen MMS cases were performed on 754 patients. Three hundred four cases were performed pre-COVID and 515 during COVID. Sixty-nine cases (22.7%) were performed on mask-covered facial locations pre-COVID with 100 such cases (19.4%) performed during COVID. For mask-covered sites, there were no significant differences in baseline demographics, skin cancer type, or surgical repair technique pre-COVID versus COVID (p < .05 for all) (Table 1).
TABLE 1.
Demographic, Procedure, and Surgical Site Infection Data
| All Cases | Mask Location Cases | |||||
| Pre-COVID (n = 304) | COVID (n = 515) | p* | Pre-COVID (n = 69) | COVID (n = 100) | p* | |
| Age (median) | 67 | 70 | .15 | 63 | 66 | .09 |
| Gender | .02 | NS | ||||
| Male | 167 (55%) | 325 (64%) | 28 (41%) | 49 (49%) | ||
| Female | 137 (45%) | 187 (36%) | 41 (59%) | 51 (51%) | ||
| Cancer type | NS | NS | ||||
| BCC | 178 (59%) | 295 (57%) | 58 (84%) | 77 (77%) | ||
| SCC/SCC in situ | 124 (40%) | 213 (42%) | 11 (16%) | 23 (23%) | ||
| Others | 2 (1%) | 6 (1%) | 0 (0%) | 0 (0%) | ||
| Location | NS | |||||
| Mask location | 69 (23%) | 100 (19%) | — | — | ||
| Nonmask location | 235 (77%) | 415 (81%) | — | — | ||
| Mask location | NS | NS | ||||
| Nose | 57 (19%) | 79 (15%) | 57 (83%) | 79 (79%) | ||
| Nasolabial fold | 2 (1%) | 3 (1%) | 2 (3%) | 3 (3%) | ||
| Lip | 7 (2%) | 14 (3%) | 7 (10%) | 14 (14%) | ||
| Chin | 3 (1%) | 4 (1%) | 3 (4%) | 4 (4%) | ||
| Repair type | NS | NS | ||||
| Second intention | 20 (7%) | 12 (2%) | 4 (6%) | 1 (1%) | ||
| Linear closure | 218 (72%) | 395 (77%) | 34 (49%) | 51 (51%) | ||
| Flap or graft | 66 (22%) | 108 (21%) | 31 (45%) | 48 (48%) | ||
| Surgical site infections† | 7 (2%) | 9 (2%) | NS | 0 (0%) | 4 (4%) | .09 |
| Gram-negative infection | 3/7 (43%) | 7/9 (78%) | NS | 0 (0%) | 4/4 (100%) | .09 |
| Others | 4/7 (57%) | 2/9 (22%) | 0 (0%) | 0 (0%) | ||
*p-values reported as nonsignificant (NS) if p > .15. Values reported for p ≤ .15.
†Bacterial culture data reported as a proportion of cases with surgical site infection.
Sixteen SSIs occurred, with 7 (2.3%) and 9 (1.7%) occurring during the premask and mask periods, respectively. For mask-covered locations, infection occurred in 0/69 cases pre-COVID (0%) versus 4/100 cases during COVID (4%) (p = .09) (Table 1). Mask location SSIs composed 44.4% of total infections during COVID. All mask location SSIs during the mask period were caused by gram-negative organisms, with Pseudomonas aeruginosa (n = 2) and Enterobacter (n = 2) species isolated. Three of 7 SSIs (42.9%) in the pre-COVID period were caused by gram-negative bacteria versus 7 of 9 SSIs (77.8%) during COVID (p = .15) (Table 1). Antibiotic prophylaxis management did not change during the 2 periods.
Seven infections occurred in nonmask locations pre-COVID (100%) and 5 occurred in nonmask locations during COVID (55.5%) (Table 1). Causative organisms for nonmask location infections pre-COVID included methicillin-sensitive Staphylococcus aureus (n = 2), mixed aerobic and anaerobic bacteria (n = 2), P. aeruginosa (n = 2), Bacteroides fragilis (n = 1), Enterobacter cloacae (n = 1), and Escherichia coli (n = 1). Causative organisms for nonmask location infections during COVID included methicillin-sensitive S. aureus (n = 2), E. coli (n = 1), P. aeruginosa (n = 1), Klebsiella oxytoca (n = 1), and Proteus mirabilis (n = 1).
Discussion
Facial masks are a vital tool in limiting the transmission of severe acute respiratory syndrome coronavirus 2. Widespread, the regular use of face masks represents a significant behavioral change for most dermatologic surgery patients. At our institution, a mask requirement for health care workers and patients was issued on May 6, 2020, in addition to mandates issued by local public health authorities. After the universal mask mandate, we observed an increased rate of SSIs at mask-covered areas of the face compared with a similar time period before widespread facial mask usage. Interestingly, a higher proportion (77.8% vs 42.9%) of gram-negative bacterial infections was identified during the COVID period, and either P. aeruginosa or Enterobacter species were isolated in all mask location cases.
Although relatively rare, SSIs are the most common complication after MMS, with previously reported infection rates ranging from 0.4% to 2.5%.3,4 Known potential risk factors for post-MMS infections include wedge excisions of the lip, flaps performed on the nose, as well as skin grafting and pre-existing patient comorbidities.5 However, in this study, repair types were similar for surgical defects within masked sites during both the premask and mask periods. In addition, there were no identified comorbidities among the patients who developed masked site SSIs. Antibiotic prophylaxis management did not change during the 2 periods.
Although the underlying mechanisms remain unclear, our findings suggest that the occlusive environment generated by mid and lower face masking may have potential implications, not only for the incidence of SSIs but also for the etiologic bacterial agents as well. The increased propensity toward gram-negative infections, whether related to resident oral flora, mask-mediated abrasions, or simply frequently used but infrequently laundered facial masks, may require alternative considerations in postoperative antimicrobial management. As facial masks will likely remain necessary for the foreseeable future, larger studies are needed to further elucidate the potential role of facial masking on SSIs.
Limitations
Limitations of this study include the small sample size and variability in the patient mask type and wearing habits. The potential for selection bias and increased vigilance in tracking SSIs on mask-covered sites during the COVID period must be considered; however, the retrospective nature of this study and lack of change in clinical practices pertaining to SSI diagnosis during the pre-COVID and COVID periods greatly mitigate this risk.
Conclusion
In this retrospective study of 819 MMS cases, there was an increase in the rate of SSI on the mask-covered face during the COVID-19 pandemic that approached statistical significance (0 vs 4%). All mask-covered face infections were caused by gram-negative bacteria. The mechanism underlying these findings, whether directly mask related or secondary to changes in patient behaviors, remains unclear. Larger studies are needed to further elucidate the potential role of facial masking on SSIs.
Footnotes
B. C. Baumann received honoraria from Mevion, and B. C. Baumann and K. M. MacArthur received consulting fees from Sanofi/Regeneron, all outside of the scope of the submitted work. The remaining authors have indicated no significant interest with commercial supporters.
Contributor Information
Stephen P. Erickson, Email: ericksons@wustl.edu.
James P. Foshee, Email: jpfoshee@wustl.edu.
Brian C. Baumann, Email: brian.baumann@wustl.edu.
Martha L. Council, Email: mcouncil@wustl.edu.
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