Comparison of three rapid and easy bacterial DNA extraction methods for use with quantitative real-time PCR

The development of fast and easy on-site molecular detection and quantification methods for hazardous microbes on solid surfaces is desirable for several applications where specialised laboratory facilities are absent. The quantification of bacterial contamination necessitates the assessment of the efficiency of the used methodology as a whole, including the preceding steps of sampling and sample processing. We used quantitative real-time polymerase chain reaction (qrtPCR) for Escherichia coli and Staphylococcus aureus to measure the recovery of DNA from defined numbers of bacterial cells that were subjected to three different DNA extraction methods: the QIAamp® DNA Mini Kit, Reischl et al.’s method and FTA® Elute. FTA® Elute significantly showed the highest median DNA extraction efficiency of 76.9% for E. coli and 108.9% for S. aureus. The Reischl et al. method and QIAamp® DNA Mini Kit inhibited the E. coli qrtPCR assay with a 10-fold decrease of detectable DNA. None of the methods inhibited the S. aureus qrtPCR assay. The FTA® Elute applicability was demonstrated with swab samples taken from the International Space Station (ISS) interior. Overall, the FTA® Elute method was found to be the most suitable to selected criteria in terms of rapidity, easiness of use, DNA extraction efficiency, toxicity, and transport and storage conditions

Evaluation of a nitrite-free commercial preparation in the production of swine and roe deer ( Capreolus capreolus

The aim of this study was to compare the effect of a commercial formulation consisting of natural ingredients and dextrose on the production of salami. We analysed the effect on microbiological, physico-chemical and sensorial properties in the production of nitrite-free swine and roe deer (Capreolus capreolus) salami. Six batches of salami were prepared: four with the addition of starter cultures and diverse substrates (no substrate, skimmed milk, commercial formulation and dextrose) and two without starter cultures as controls (one without substrate and one with skimmed milk). Samples for microbiological and physico-chemical analysis were taken on day 0, day 5 and day 25. A sensory evaluation was performed at the end of the ripening process. The best results regarding the changes in the microbiota were observed in the batch produced with the addition of skimmed milk (final concentration for Pseudomonas spp. was 3.07 ± 1.11 log cfu g−1, for Enterobacteriaceae was 1.57 ± 0.51 log cfu g−1 and the total coliforms were undetectable). As regards the sensory evaluation, the best scores (in particular colour uniformity, fat/lean distribution and mould flavour) were assigned to the salami produced with the addition of dextrose. According to the results obtained in this study, the addition of the commercial formulation to manufacture nitrite and nitrate-free, dry-cured swine and roe deer salami led to no significant effects on their microbiological and sensory characteristics. Overall, the results obtained with the addition of the commercial formulation were very similar to those obtained by adding dextrose, which is the main component of the formulation itself.HIGHLIGHTS The effect of a commercial formulation on microbiological, chemical and sensory characteristics of nitrite-free swine and roe deer (Capreolus capreolus) salami was analysed. The results obtained with the addition of the commercial formulation were very similar to those obtained by simply adding dextrose or just skimmed milk. The use of commercial preparation seems therefore not worthwhile

Influence of autochthonous starter cultures on microbial dynamics and chemical-physical features of traditional fermented sausages of Basilicata region

In this study, a combination of a Lactobacillus sakei strain and a Staphylococcus equorumstrain was used as autochthonous starter for an experimental production of Basilicata fermented sausages. The influence of starter addition on the safety and quality parameters and microbiological and chemical-physical properties of the products was investigated. Microbial counts of safety indicators were lower in the samples with the addition of starter culture, and, at the end of ripening, Enterobacteriaceae and Gram negative bacteria were detected only in samples made without the starter addition. The addition of starter led to a final product with better microbiological and chemical-physical features, and a positive effect on flavor and aroma compounds formation by a good proteolytic and lipolytic activities. The use of autochthonous starter cultures allows to obtain products with the organoleptic characteristics expected and steady in time and to standardize the production process, improving the safety and quality, but preserving the essential character of the product