Sample Preparation – An Essential Prerequisite for High-Quality Bacteria Detection

Abstract

Rapid microbial testing is more and more preferred worldwide. Conventional time-consuming methods with detection times taking up to several days are being replaced by rapid tests that take only a few hours. With the development of new, rapid, and accurate methods for the detection of bacterial contaminants, the requirements for sample preparation techniques are more and more challenging. In fact, sample preparation is the critical step with respect to the applicability of novel methods. Sample preparation comprises sampling/sample drawing, sample handling, and sample preparation. To fulfil the demands of modern microbiology the ideal procedure should permit rapidly providing the processed sample in a small volume which contains the analyte in the highest concentration possible. The analyte has to be free of substances interfering with the detection method to be finally applied. Additionally, sample processing procedures used should not result in any loss of the bacterial analyte, thereby enabling quantitative measurements. Techniques for the preparation of samples subjected to microbiological examination are described, especially focusing on the methods applied to investigate the occurrence of pathogenic organisms in foods as well as in the food processing environment. Sample drawing methods for the monitoring of air and surfaces are outlined. Moreover, different sample preparation methods intended to be carried out prior to the detection of intact bacterial cells or bacterial nucleic acids are discussed in detail. Special attention is paid to magnetic particle-based separation methods, as these tools have gained increasing importance due to their outstanding advantages.