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SAN ANTONIO -- Face masks became seeded "almost instantaneously" with oral and nasopharyngeal bacteria, posing a potential risk of spread to the eyes during intravitreal injections for macular degeneration, according to a study reported here.

Masks for all 73 patients involved in the study tested positive for a variety of common organisms, as well as some uncommon microbes. Bacteria grew on both sides of masks, irrespective of mask material age.

Despite the proximity to infectious organisms, no patient developed endophthalmitis, reported Avinash V. Honasoge, MD, PhD, of the Retina Institute of St. Louis, at the American Society of Retina Specialists (ASRS) meeting.

"We didn't find a correlation between mask age and inside or outside growth, which suggests [other evidence] that even within a few hours of wearing a mask, you can see bacteria on them," he said. "Men did have greater inside-mask growth than women. This has previously been speculated to be due to facial hair."

"Everybody here is doing intravitreal injections, and you'll have to make a choice," Honasoge added. "How are you going to try and protect the periocular surface after you've sterilized it with iodine? Are you going to tape the mask, institute a no-talking policy? Perhaps just remove the mask and dilute the particulate matter and away from the periocular space? The other question is, as this pandemic continues, will we see a change in the flora that are present for our post-injection endophthalmitis?"

The COVID-19 pandemic has led to widespread use of face masks, made of a variety of materials and of varying quality. Ill-fitting masks pose an obvious risk to patients during intravitreal injections. Changing masks is not a solution, he continued. Within hours of putting on a fresh mask, bacterial RNA can be isolated, and bacteria can adhere to a mask for hours after wearing.

"While masks are very good at blocking forward transmission, if you don't tape a mask or you have a poorly fitted mask, you can get an upward flow of particulate matter," said Honasoge. "Not talking seems to help. Taping seems to help, but the question we had is what kind of bacteria are we dealing with. Is it truly just ordinary flora or are we dealing with new bugs that may cause more virulent endophthalmitis?"

To exam the issues of bacterial variety and quantity, investigators prospectively evaluated 73 patients with appointments for intravitreal injections. Patients with N95/KN95 masks were excluded, as were patients receiving intravitreal antibiotic injections endophthalmitis.

Patients' masks were swabbed on the inside and outside and evaluated for gram stain, aerobic culture, and speciation. The primary outcomes were bacterial composition and mask growth.

The study population had a median age of 76-77, and mask material was cloth in 31 cases; surgical in 42. Mask age ranged from less than 1 day to more than a month. More than a third of the masks had been worn a week or longer. One patient had not washed his cloth mask in more than a year.

Laboratory analysis showed bacterial growth on the inside of 97.2% of the masks and 90.2% of the outside. Some masks had bacteria on the inside and outside and some had more than one type of bacteria.

"The bacteria included the usual suspects, such as coagulase-negative staph and strep viridans, but also some of the kind of bad players -- enterobacter, E. coli, bacillus. Each mask had between one and two species on each side of the mask."

Quantification studies suggested heavy growth on both the inside and outside of the masks, he added.

A second study reported at the same ASRS "Inflammatory and Infectious Diseases Symposium," provided additional evidence of upward dispersion of microbes by patients wearing masks during simulated intravitreal injections. The study involved 15 healthy volunteers who wore different types of masks, with and without taping, and with and without a no-talking setting (the latter consisting of a standardized script).

Altogether, the patients participated in evaluation of six mask scenarios, said Samir Patel, MD, of Mid-Atlantic Retina, Wills Eye Hospital and Thomas Jefferson University, both in Philadelphia. Culture plates were secured to each participant's forehead, and the plates were cultured for aerobic and anaerobic species. A total of 90 cultures were obtained during each of the no-talking and talking settings.

The results showed that a tight-fitting mask taped at the top and an N95 mask performed best, and both were associated with an average of 0.20 colony-forming units (CFUs) during the no-talking setting. The N95 performed numerically better during the talking simulation, but did not differ significantly from the tight-fitting mask with taping (0.20 vs 0.27 CFU). A tight-fitting mask without tape performed significantly worse (1.13 CFU with no talking, 1.40 CFU with talking, P<0.01) and was similar to no mask, a loose-fitting mask, or a cloth mask.

The most commonly isolated organisms during talking and no-talking simulations were Staphylococcal spp (51-64%).

"There was no difference in bacterial dispersion between tight-fitting surgical face masks with tape and N95 face masks," said Patel. "Taping the superior portion of the patient's face mask may limit bacterial dispersion when performing intravitreal injections. However, the clinical implications of these findings are unknown, and it is unclear whether alterations in the number of colony-forming units around the eye necessarily alters the clinical risk of endophthalmitis."