Development of a qualitative real-time PCR for microbiological quality control testing in mammalian cell culture...

The aim of this study was to develop and evaluate a real-time PCR technology for microbiological control methods to examine individualized cell therapeutics, an emerging class of pharmaceutical formulations.

Oligonucleotide primers and hybridization probe for bacterial detection targeting the 16SrRNA gene were adapted based on Nadkarni et al. [Microbiology148 (2002) 257]. For detection of yeast and moulds, primers and probe were designed from conserved sequences of the 18SrRNA gene in this study. The real-time PCR assays were tested on genomic DNA of Escherichia coli and Candida albicans to assess efficiency and linear dynamic range. After successful establishment of robust real-time PCRs, applicability of the assays was evaluated by extracting microbial target DNA from cell-based preparations. Different commercial DNA extraction methods were compared identifying the MagNA Pure DNA Isolation Kit III as the method of choice. Sensitivity was examined for different strains and a detection limit of 10² -10³ CFU per ml in a sample containing ~10⁶ mammalian cells per ml was achieved.

This study reports the successful establishment of two qualitative real-time PCR assays, enabling in general the broad-range detection of microbial contaminants in a cell-based sample matrix.

Individualized cell therapeutics tend to have a short shelf life. Due to lengthy incubation periods, compendial testing according to current pharmacopoeial guidelines may not be applicable. We report a suitable alternative method upon which future microbiological quality control methods for such products could be based on. However, to implement valid rapid microbiological testing methods using real-time PCR technology, further challenges need to be addressed.