Evidence for the absence of Staphylococcus aureus in land applied biosolids

Staphylococcus aureus is an important human pathogen both within the hospital setting and as a community-acquired infection. Recently there has been concern that land applied biosolids may transmit S. aureus. However, no scientific data are available to document whether biosolids are a source of S. aureus. To determine if S. aureus is present in biosolids, we collected samples from 15 sites across the United States. Samples analyzed were as follows: 3 raw untreated sewage samples and 2 undigested primary sewage sludge samples; 23 different biosolid samples; and 27 aerosols obtained during biosolid land application (biosolid aerosols). Although S. aureus were detected in raw sewage samples, none were found in any of the treated biosolids nor in any biosolid aerosol samples. These results suggest that biosolids are not a likely source of S. aureus human exposure or infection.