How often should phosphor plates be sterilized?

Is weekly gas sterilization enough to prevent microbial contamination of a phosphor plate system?

Researchers from the Medical College of Georgia School of Dentistry tackle this question in a new study published in Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics (January 8, 2010).

Sajitha Kalathingal, B.D.S., M.S., and colleagues set out to determine the rate and source of microbiologic contamination of photostimulable phosphor plates (PSP) in a predoctoral clinic, and whether a combination of weekly gas sterilization and barrier protocols can prevent contamination of PSP plates.

Fifty plates in clinical use and 25 gas-sterilized control plates were pressed onto a blood agar medium and incubated at 37° C. The number, size, distribution, and variety of resulting bacterial colonies were noted. To test whether these bacteria could have come from oral sources, the researchers selected 17 colonies for culture on Mitis Salivarius (M-S) agar.

They found that 28 test plates (56%) exhibited growth of bacterial colonies on blood agar. Of the 17 colonies selected for growth on M-S agar, 13 (76.47%) showed growth, with 69% of them gram-positive.

"Our results indicate [the need for] reinforcing standard precautions of infection control for intraoral radiography," the researchers wrote.

One potential solution, they added, is daily rather than weekly gas sterilization of plates after clinical use.

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