Comparative analysis and limitations of ethidium monoazide and propidium monoazide treatments for the differentiation of viable and nonviable campylobacter cells. 2014

Diana Seinige, and Carsten Krischek, and Günter Klein, and Corinna Kehrenberg
Institute for Food Quality and Food Safety, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany.

The lack of differentiation between viable and nonviable bacterial cells limits the implementation of PCR-based methods for routine diagnostic approaches. Recently, the combination of a quantitative real-time PCR (qPCR) and ethidium monoazide (EMA) or propidium monoazide (PMA) pretreatment has been described to circumvent this disadvantage. In regard to the suitability of this approach for Campylobacter spp., conflicting results have been reported. Thus, we compared the suitabilities of EMA and PMA in various concentrations for a Campylobacter viability qPCR method. The presence of either intercalating dye, EMA or PMA, leads to concentration-dependent shifts toward higher threshold cycle (CT) values, especially after EMA treatment. However, regression analysis resulted in high correlation coefficient (R(2)) values of 0.99 (EMA) and 0.98 (PMA) between Campylobacter counts determined by qPCR and culture-based enumeration. EMA (10 μg/ml) and PMA (51.10 μg/ml) removed DNA selectively from nonviable cells in mixed samples at viable/nonviable ratios of up to 1:1,000. The optimized EMA protocol was successfully applied to 16 Campylobacter jejuni and Campylobacter coli field isolates from poultry and indicated the applicability for field isolates as well. EMA-qPCR and culture-based enumeration of Campylobacter spiked chicken leg quarters resulted in comparable bacterial cell counts. The correlation coefficient between the two analytical methods was 0.95. Nevertheless, larger amounts of nonviable cells (>10(4)) resulted in an incomplete qPCR signal reduction, representing a serious methodological limitation, but double staining with EMA considerably improved the signal inhibition. Hence, the proposed Campylobacter viability EMA-qPCR provides a promising rapid method for diagnostic applications, but further research is needed to circumvent the limitation.

UI MeSH Term Description Entries
D011419 Propidium Quaternary ammonium analog of ethidium; an intercalating dye with a specific affinity to certain forms of DNA and, used as diiodide, to separate them in density gradients; also forms fluorescent complexes with cholinesterase which it inhibits. Propidium Diiodide,Propidium Iodide,Diiodide, Propidium,Iodide, Propidium
D002470 Cell Survival The span of viability of a cell characterized by the capacity to perform certain functions such as metabolism, growth, reproduction, some form of responsiveness, and adaptability. Cell Viability,Cell Viabilities,Survival, Cell,Viabilities, Cell,Viability, Cell
D002645 Chickens Common name for the species Gallus gallus, the domestic fowl, in the family Phasianidae, order GALLIFORMES. It is descended from the red jungle fowl of SOUTHEAST ASIA. Gallus gallus,Gallus domesticus,Gallus gallus domesticus,Chicken
D004791 Enzyme Inhibitors Compounds or agents that combine with an enzyme in such a manner as to prevent the normal substrate-enzyme combination and the catalytic reaction. Enzyme Inhibitor,Inhibitor, Enzyme,Inhibitors, Enzyme
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D001386 Azides Organic or inorganic compounds that contain the -N3 group. Azide
D013194 Staining and Labeling The marking of biological material with a dye or other reagent for the purpose of identifying and quantitating components of tissues, cells or their extracts. Histological Labeling,Staining,Histological Labelings,Labeling and Staining,Labeling, Histological,Labelings, Histological,Stainings
D016123 Campylobacter jejuni A species of bacteria that resemble small tightly coiled spirals. Its organisms are known to cause abortion in sheep and fever and enteritis in man and may be associated with enteric diseases of calves, lambs, and other animals. Campylobacter fetus subsp. jejuni,Vibrio hepaticus,Vibrio jejuni
D017000 Campylobacter coli A species of gram-negative, rod-shaped bacteria isolated from the intestinal tract of swine, poultry, and man. It may be pathogenic. Vibrio coli
D058491 Bacterial Load Measurable quantity of bacteria in an object, organism, or organism compartment. Bacterial Count,Bacterial Counts,Count, Bacterial,Counts, Bacterial,Bacterial Loads,Load, Bacterial,Loads, Bacterial

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