4. Food sample pretreatment prior to FISH analysis
The pretreatment of the food matrix has been shown to be crucial for the successful detection of bacteria (Table 1). Low numbers of the target organism require the concentration of the pathogen, and huge amounts of protein and fat have to be removed
since they might disturb the hybridization of the probes. Other food components with natural fluorescence activity (e.g. chlorophyll in plant material, hemoglobin in meat and other pigments) can cause strong background in the consecutive microscopic examination. The overall accessibility and the physical properties of the target
pathogen have to be taken into account and adequate steps for the extraction of the microbes might be necessary, especially if cultureindependent FISH analyses are performed. Moreover, dilution effects as a result of sample pretreatment have to be minimized. In conclusion, a quick and suitable sample pretreatment is as necessary
as for other detection methods, for example PCR. Despite its paramount importance, there are no generally followed matrixspecific protocols for the pretreatment of food prior to FISH analysis.
The most simple, but also very time-consuming, way to perform a FISH analysis is based on the plate-picking of bacterial colonies which were isolated out of food samples (Zhang et al.,2012). However, approaches which directly use the food matrix
are much more preferable
4. Food sample pretreatment prior to FISH analysisThe pretreatment of the food matrix has been shown to be crucial for the successful detection of bacteria (Table 1). Low numbers of the target organism require the concentration of the pathogen, and huge amounts of protein and fat have to be removedsince they might disturb the hybridization of the probes. Other food components with natural fluorescence activity (e.g. chlorophyll in plant material, hemoglobin in meat and other pigments) can cause strong background in the consecutive microscopic examination. The overall accessibility and the physical properties of the targetpathogen have to be taken into account and adequate steps for the extraction of the microbes might be necessary, especially if cultureindependent FISH analyses are performed. Moreover, dilution effects as a result of sample pretreatment have to be minimized. In conclusion, a quick and suitable sample pretreatment is as necessaryas for other detection methods, for example PCR. Despite its paramount importance, there are no generally followed matrixspecific protocols for the pretreatment of food prior to FISH analysis.The most simple, but also very time-consuming, way to perform a FISH analysis is based on the plate-picking of bacterial colonies which were isolated out of food samples (Zhang et al.,2012). However, approaches which directly use the food matrixare much more preferable
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