ABSTRACT
AIMS: 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. METHODS AND RESULTS: 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. CONCLUSIONS: 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. SIGNIFICANCE AND IMPACT OF THE STUDY: 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.
Subject(s)
Bacteria/isolation & purification , Cell Culture Techniques/standards , Fungi/isolation & purification , Real-Time Polymerase Chain Reaction/methods , Candida albicans/genetics , Candida albicans/isolation & purification , Cells, Cultured , DNA/isolation & purification , DNA Primers , Escherichia coli/genetics , Escherichia coli/isolation & purification , Humans , Limit of Detection , Microbiological Techniques/standards , Quality Control , RNA, Ribosomal, 16S/genetics , RNA, Ribosomal, 18S/genetics , Sensitivity and SpecificityABSTRACT
Technical developments in molecular biology have found extensive applications in the field of microbial ecology. Among these techniques, fingerprinting methods such as denaturing gel electrophoresis (DGE, including the three options: DGGE, TGGE and TTGE) has been applied to environmental samples over this last decade. Microbial ecologists took advantage of this technique, originally developed for the detection of single mutations, for the analysis of whole bacterial communities. However, until recently, the results of these high quality fingerprinting patterns were restricted to a visual interpretation, neglecting the analytical potential of the method in terms of statistical significance and ecological interpretation. A brief recall is presented here about the principles and limitations of DGE fingerprinting analysis, with an emphasis on the need of standardization of the whole analytical process. The main content focuses on statistical strategies for analysing the gel patterns, from single band examination to the analysis of whole fingerprinting profiles. Applying statistical method make the DGE fingerprinting technique a promising tool. Numerous samples can be analysed simultaneously, permitting the monitoring of microbial communities or simply bacterial groups for which occurrence and relative frequency are affected by any environmental parameter. As previously applied in the fields of plant and animal ecology, the use of statistics provides a significant advantage for the non-ambiguous interpretation of the spatial and temporal functioning of microbial communities.
