A Survey of Microbial Popluations in Infilled Synthetic Turf Fields

Staphylococcus aureus is a bacterium that is a common inhabitant of human skin and can cause various types of skin or soft tissue infections (Marples, et al, 1990). S. aureus has also been implicated in certain types of food poisoning (Bennet and Lancette, 1998) and in serious medical problems such as toxic shock syndrome. Strains of S. aureus that are resistant to common antibiotics are becoming more common, particularly in medical settings. There have been reports recently of methicillin-resistant S. aureus causing infection in athletes (Begier, et al, 2004). With the increase in athlete infections, there is growing concern regarding the role of infilled turf systems (Seppa, 2005). While there is some indication that the source of these bacteria may be more closely associated with locker room activity than with the infill system (Begier, et al, 2004; Kazakova, et al, 2005), conclusive evidence is not currently available.

The objective of this survey was to determine the microbial population of several infilled synthetic turf systems as well as natural turfgrass fields. In addition, other surfaces from public areas and from an athletic training facility were also sampled. Colonies suspected to be S. aureus were positively or negatively identified.

Materials & Methods

Sample Collection

All samples in this study were collected between June 15 and June 30, 2006. Infilled synthetic turf systems were located at facilities in Pennsylvania and were in use by all levels of play ranging from elementary to professional athletes. Infill material samples were collected from both a ‘high use’ and a ‘low use’ area of each field. A ‘high use’ area typically was a goal mouth or, for a football only field, an area between the 30- and 40-yard lines between the hash marks. A ‘low use’ area was typically an area toward the edge of the field (but within the field of play) or an end zone. Approximately 2–3 ml of infill material were removed from each area of the field using a sterile test tube inserted directly into the infill. Pile fiber samples were also collected from many fields by clipping several fibers from the backing and transferring the fibers to a sterile test tube. Samples were stored in a cooler and processed as soon after collection as possible.

Sample Processing

Approximately 0.075 g of infill material was transferred to a test tube containing 10 ml sterile 0.1% peptone broth. The sample was agitated for 30 seconds Serial dilutions of each sample were plated up to 10-3 on both R2A agar for total organism populations and Baird-Parker agar, a selective media for Staphylococcus (Bennet and Lancette, 1998). Duplicate platings were made for each media and each dilution. Petri plates were parafilmed and incubated at room temperature and colony counts were made 72 hours after processing. Samples on Baird-Parker agar were also observed again after 5 days. Calculations were then made to determine the number of colony forming units (CFU) per gram of infill material.

For comparison purposes, soil samples were also collected from a native soil and a sand based natural turfgrass athletic field. Samples were processed in the same manner as the infill material samples with 0.2 grams of soil being used for processing.

Sampling of Other Surfaces

Samples were collected from common surfaces in public areas as well as from various surfaces in an athletic training area. Samples were collected by swabbing surfaces with sterile cotton swabs. Random individuals were also tested by swabbing hands and/ or face. Both R2A and Baird-Parker agar plates were wiped with the sterile swabs. Plates were incubated at room temperature and colony counts were conducted after 72 hours for R2A agar and again at 5 days for Baird-Parker media.

Identification of Staphylococcus aureus colonies

Gram stains and latex agglutination tests (Essers and Radebold, 1980) were performed on colonies suspected of being S. aureus. Several potential S. aureus colonies isolated from hand and facial swabs were also included in the testing.