Abstract
Contact plates, dipslides and swabs are used for the microbiological monitoring of surfaces in controlled environments such as pharmaceutical clean rooms. In the present study, three different swab types using two different methods (direct streaking on agar versus elution followed by membrane filtration) were evaluated. In a first study, representative surfaces in pharmaceutical clean rooms were artificially inoculated using three different environmental strains (in vitro study). In a second study, a naturally inoculated floor was swabbed with the same three swab types, again using the two different recovery methods (in situ study). With the in vitro study, clear differences were found between the three swab types as well as between the two recovery methods. In addition, recovery rate of the swab type was dependent on the recovery method (interactive effect). One swab type showed a higher recovery rate with direct streaking on agar, while the other swabs showed better results using the elution/membrane filtration method. This difference can be explained by the fact that both swabs were each developed for their specific application. The type of surface also had a highly significant effect on the recovery rates. Recovery on stainless steel was better than for the other surfaces, while lexan had the lowest recovery rate. From the three different strains applied in the in vitro study, Micrococcus luteus had significantly higher recovery results compared to the other two strains (Bacillus thuringiensis, Aspergillus brasiliensis). The differences in recovery between the swab type and recovery method were less pronounced in the in situ study. In particular, the recovery of the swab type depending on the recovery method was not found. In conclusion, if swabs are to be used for environmental monitoring, their suitability should first be evaluated. This can be approached with artificially inoculated surfaces. However, naturally inoculated surfaces might be more realistic and might better reflect what is found in pharmaceutical clean rooms.
- in situ study
- membrane filtration
- microbiological environmental monitoring
- recovery rate
- streak on agar
- swab
- Received June 2, 2016.
- Accepted August 8, 2016.
- Copyright © 2016, Parenteral Drug Association
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