An evaluation of microbiologic contamination on a phosphor plate system: is weekly gas sterilization enough?

Objective: This study was performed to determine: 1) the rate and source of microbiologic contamination of photostimulable phosphor plates (PSP) in a predoctoral clinic; and 2) whether a combination of weekly gas sterilization and barrier protocols can prevent contamination of PSP plates. Methods: Fifty plates in clinical use and 25 gas-sterilized control plates were selected for examination. The PSP plates were pressed onto blood agar medium and incubated at 37°C. The number, size, distribution, and variety of resulting colonies were noted. To test whether these bacteria could have come from oral sources, 17 colonies were selected for culture on Mitis-Salivarius (M-S) agar. Those colonies that grew on the M-S agar were Gram stained. Results: Twenty-eight test plates (56%) exhibited growth of bacterial colonies on blood agar. Seventeen of those bacterial colonies were selected for growth on M-S agar, and 13 (76.47%) showed growth, 69% of them gram positive. Conclusion: Our results indicate reinforcing standard precautions of infection control for intraoral radiography, and that gas sterilization of plates after each day's clinical use is a potential solution.