Biological Evaluation of Carpeting

Studies of microbial contamination were carried out on a carpet strip (acrilan) installed in a laboratory corridor and on two carpet strips (acrilan and wool) installed in two rooms in a pediatric hospital. A sampling procedure of randomly removing 8-mm plugs from the carpets was used for subsequent enumeration and identification of contaminating microorganisms. Microbial counts increased with time, reached a "plateau" at about 4 weeks, and appeared to be related to the amount of activity present in the carpeted area. Vacuuming of carpets showed only a slight reduction in the number of recoverable microorganisms. Qualitative studies on a strip of acrilan carpet installed in a hospital room indicated that Staphylococcus epidermidis and gram-positive nonsporeforming rods were the predominating microorganisms. Coagulase-positive S. aureus organisms were isolated during every sampling period, and gram-negative rods were also regularly isolated. Most nitrate-reducing gram-negative rods belonged to the Enterobacter and Escherichia groups. Survival studies conducted on carpet strips after hospital installation showed relatively constant levels of contamination for about 6 weeks, followed by a gradual reduction in numbers; coagulase-positive S. aureus were found for 35 days, whereas the proportions of most organisms remained relatively constant with time.