Objective: Germitec has developed a new disinfection process (AS 1) based on UV-C radiation for the disinfection of external and endocavitary ultrasound probes. The objective of this study was to evaluate the efficacy of this alternative procedure according to a test method based on carrier tests currently used in Europe for the evaluation of chemical disinfectants.
Methods: 4 cm² predefined surface of a frosted glass carrier were inoculated with 50 µl of a test suspension containing about 3.0 x 105 CFU/carrier and 10% of bovine serum albumin. Contaminated carriers are maintained at room temperature until complete drying and submitted to UVC treatment in the AS 1 chamber. After treatment, glass carriers are transferred into 10 ml of recovery solution and 1 ml of glass beads and the number of viable microorganisms is determined after tenfold serial dilutions, using the pour plate technique. After incubation, plates are counted and results are expressed as a number of colony forming units per carrier.
Results: results obtained demonstrate a 4.0-log10 reduction for Mycobacterium avium CIP 105415 and Mycobacterium terrae CIP 104321 within 60 seconds of treatment and within 180 seconds for Aspergillus niger IP 1431.83 spores. After a 60 seconds exposure time in the AS 1 a 5.0-log10 reduction was obtained for glass carriers contaminated with Escherichia coli CIP 54127.
Conclusions: The efficacy levels reached are comparable to log reductions required in Europe for a liquid chemical disinfectant used on semicritical devices. Nevertheless, according to others standard like ISO 15883-4 or AOAC, higher efficacy levels should be reached (i.e. 5.0- to 6.0-log10 reduction on Mycobacterium sp.). This study demonstrates the need to define the antimicrobial efficacy levels required for such non-chemical disinfection processes used on simple medical devices and for which the use of probe covers/condom and cleaning before disinfection is always recommended.