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Discussion

Considering the data in Table 1, the number of total colonies detected varied considerably between sites. In most cases, the number of total microbes at a given site was similar for both high use and low use areas of the field. In general, indoor fields tended to have lower overall microbial populations (0–7267 CFU) than outdoor fields. At one facility where indoor and outdoor fields were sampled on the same day, the indoor fields contained 0–67 CFU/g crumb rubber, while the outdoor field contained 2.8–3.3×104 CFU/g crumb rubber. While indoor fields represent only 20% of the fields sampled in this study a consistent trend is apparent.

Total microbial populations for the two natural turf athletic fields were an order of magnitude higher than populations for the infill systems with the highest numbers. Also, observationally, there appeared to be a greater diversity in the types of organisms isolated from soil samples than crumb rubber samples. However, no specific determinations of any cultures were made other than to positively or negatively identify S. aureus.

One factor that may influence total microbial populations of infill surfaces is use. Of the 11 fields with at least one subsample having greater than 1×104 CFU/g crumb rubber, one of those fields had been heavily used within 7 days of sampling and two fields had been used within 24 hours of sampling. Tracking microbial population fluctuations of a field over time may be of interest.

It is perhaps not surprising that no S. aureus colonies were found on any fields, given that the temperature range for growth of S. aureus is 7–48°C, with the optimal temperature for growth being 37°C (Baird-Parker, 1990). Surface temperatures of infill surfaces outdoors often exceed the temperature range of S. aureus (McNitt, 2005). However, high surface temperatures do not explain the relatively low numbers of total microbes on indoor playing surfaces. These low numbers may, in part, be explained by the permanently very low moisture content of indoor infilled surfaces.

In conclusion, there are generally lower numbers of total microbes present in the infill or fibers of the synthetic turf systems tested compared to natural turfgrass rootzones and Staphylococcus aureus bacterium were not found on any of the playing surfaces. Staphylococcus aureus bacterium were found on towels and other devices used by athletes.