Millipore Technical Publications |
 | Poster | |
Development of a culture media for microbiological air monitoring in isolators containing residual hydrogen peroxide | ||
| | |
| | |
| Year: | 2001 | |
Authors: Serge Ohresser, Christel Noehringer, Millipore SA France
Introduction
During microbiological air monitoring in isolators containing residual hydrogen peroxide as low as 0.3 ppm, the growth of micro-organisms can be inhibited. A media allowing the growth of micro-organisms in the presence of up to 3 ppm hydrogen peroxide is needed to avoid any false negatives.
Materials and Methods
Air monitoring in the presence of 3 ppm gaseous H2O2. 1 m3 air was sampled in isolator (Steris hyperphase VHP 1000, kindly placed at our disposal by Lilly France, Fegersheim) after a complete sterilization cycle and injection of gaseous H2O2 adjusted in order to stay at a constant 3 ppm H2O2 concentration during the entire sampling. H2O2 concentration was constantly monitored by using a PACIII system from Dräger. After air sampling, 10 to 100 cfu/plate of the following micro-organisms were spreaded on the media (TSA or TSA isolator): Staphylococcus aureus ATCC 6538, Micrococcus luteus ATCC 9341, Candida albicans ATCC 10231, Pseudomonas aeruginosa ATCC 27853, Bacillus subtlis ATCC 6633, Aspergillus niger, Staphylococcus hominis. A percentage recovery was calculated by comparing the number of cfu/plate on TSA isolator media after air monitoring in the isolator or in a laminar flow hood.
Effect of gamma-sterilization.
1 m3 air was sampled in a FRAM isolator from La Calhène after a complete sterilization cycle and ventilation to reach a 3 ppm vaporous residual H2O2 concentration. H2O2 concentration was monitored by using Dräger tubes coupled to a Dräger pump. The same micro-organisms as above were spread on gamma-sterilized and non gamma-sterilized media.
Results
We observed a complete growth inhibition on classical TSA, on all strains tested, whereas the new TSA isolator media allowed a complete recovery of bacterial growth (% recovery obtained by comparison with air monitoring in the absence of H2O2, each value representing an average of five experiments). These data were confirmed by air monitoring in isolators containing up to 8 ppm gaseous H2O2.
Figure 1: Air monitoring in the presence of 3 ppm gaseous H2O2. |
By comparing the number of cfu per plate obtained after air-monitoring in the presence of 3 ppm vaporous H2O2 on gamma-sterilized and non gamma-sterilized media (each value representing an average of six experiments), we showed that the activity of the TSA isolator media was not affected by gamma-sterilization
Fig. 2: Effect of gamma-sterilization. |
Conclusion
A new media allowing the growth of micro-organisms in the presence of up to 3 ppm vaporous or gaseous hydrogen peroxide and compatible with gamma-sterilization was developed. This media ensures the user of the absence of any false negative after air monitoring in isolators containing residual hydrogen peroxide.