Staph infection turf study yields insight in coronavirus survivability on fields
When Andrew McNitt and colleagues were conducting a study of the survivability of bacteria that cause staph infections on synthetic and natural turf football fields in 2008-09, no one had heard of COVID-19, of course. So, the question of whether the novel coronavirus that triggered the global pandemic could persist on playing surfaces and infect players was unimaginable.
The research was important, and still is, because MRSA—methicillin resistant Staphylococcus aureus—isolates have become more prevalent among athletes. The objective of the study was to examine the survival of bacteria that cause staph infections on synthetic turf systems and natural turfgrass under varying environmental conditions and to evaluate the effectiveness of various control agents applied to the synthetic turf.
When the data from that research was compiled and analyzed, it showed that staph infection isolates applied to football fields outside, on natural or synthetic turf, didn't survive long. When the bacteria were applied to turf in indoor stadiums, perhaps surprisingly, they did not fare much better. However, the Penn State professor of soil science opted not to publish the study in a scientific journal.
"I publish on many things, but with this one I decided to simply put the findings on our website and give the data to the Synthetic Turf Council," said McNitt, director of the Penn State Center for Sports Surface Research in the College of Agricultural Sciences. "So, the information got out to the people I wanted to see it, who were high school and college athletics leaders. The bottom line was that ultraviolet light kills bacteria that cause staph infections, and in indoor situations away from light, a dilute liquid detergent also was very effective."
Fast forward to late 2019, when the onset of the pandemic caused similar concerns about football players getting infected with COVID-19 from exposure to turf. Because there are similarities in the circumstances surrounding the survival of MRSA bacteria and the novel coronavirus on turf, McNitt decided to have the results of his staph bacteria and turf research peer reviewed and published.
In the resulting paper, recently published in International Turfgrass Society Research Journal, McNitt's research team reported that under nonextreme temperature and very limited light conditions, fewer than 4% of the staph infection isolates that were applied survived on both synthetic and natural turfgrass for 12 days. Applied antibacterial treatments reduced survival rates to less than 1% survival at six days for all but one treatment.
When the researchers applied bacteria that cause staph infections to outdoor surfaces in the presence of sunlight, the bacterial survival rate was reduced to less than 1% within two hours of application on synthetic turf and within three hours on natural turfgrass. Exposure to ultraviolet light and higher temperature seemed to be an effective disinfectant under the conditions of the experiment. Survival rates on synthetic and natural turfgrass did not differ greatly in indoor conditions.
Partly because of the MRSA-related turf research conducted by McNitt, who is a consultant to the National Football League, the NFL began spraying indoor fields with antimicrobial preparations such as diluted detergent solutions and disinfecting turf by slowly dragging ultraviolet light trays over playing surfaces.
"With the threat of COVID-19, the issue of fields' exposure and cleaning arose again," he said. "Studies have shown that the novel coronavirus, like MRSA, is killed by UV light, so on outdoor fields, it's not much of an issue. On indoor fields, the league continues to spray antimicrobials and disinfect with ultraviolet light trays as a precaution."
Because he did not study the novel coronavirus, McNitt has been careful about what he says regarding its ability to survive on turf, but he sees parallels between the pathogens. That is what motivated him to publish his MRSA-turf study.
"The editors really wanted to get it in the journal because there is a relationship, and there's almost nothing out there on synthetic surfaces and the diseases that get passed around," he said. "The NFL hasn't backed off its stance that it needs to use certain preventive methods as a precaution to stop COVID-19 from spreading because of turf. But the urgency of disinfecting fields has diminished as we've learned more about the disease."