Evaluation of the Novel mTA10 Selective Broth, MSB, for the Co-Enrichment and Detection of Salmonella spp., Escherichia coli O157 and Listeria monocytogenes in Ready-to-Eat Salad Samples
Author:
Costa-Ribeiro Ana12, Lamas Alexandre3ORCID, Prado Marta13ORCID, Garrido-Maestu Alejandro1ORCID
Affiliation:
1. International Iberian Nanotechnology Laboratory, Av. Mestre José Veiga s/n, 4715-330 Braga, Portugal 2. Department of Biochemistry, Genetics and Immunology, University of Vigo, 36310 Vigo, Spain 3. Food Hygiene, Inspection and Control Laboratory (Lhica), Department of Analytical Chemistry, Nutrition and Bromatology, Veterinary School, Campus Terra, University of Santiago de Compostela (USC), 27002 Lugo, Spain
Abstract
Multiplex assays implementing DNA-based methods have been demonstrated as suitable alternatives to culture-based microbiological methods; however, in most cases, they still require a suitable enrichment step. Finding suitable enrichment conditions for different bacteria may result in challenges. In the present study, a novel selective broth named MSB (mTA10 selective broth) was formulated for the simultaneous recovery of Salmonella spp., E. coli O157:H7 and L. monocytogenes. Attention was paid to ensure the optimal enrichment of L. monocytogenes as its enrichment is more challenging. To this end, cellobiose was added to increase the growth of L. monocytogenes, and sodium pyruvate was also added to improve the recovery of stressed bacteria. Four selective agents were added, namely nalidixic acid, sodium cholate, lithium chloride and potassium tellurite, to control the growth of interfering microorganisms. It was concluded that the novel broth was suitable for the simultaneous enrichment of the target pathogens, allowing them to reach concentrations higher than 7 log CFU/mL for each bacterium in pure culture. Furthermore, all heavily contaminated ready-to-eat salad samples reached concentrations higher than 5 log CFU/g. Finally, after 24 h of enrichment of spiked salad, it was possible to detect concentrations below 10 CFU/25 g.
Funder
Fundação para a Ciência e a Tecnologia project “Agenda SMARTgNOSTICS–Global Testing & Diagnostics Solutions for antimicrobial resistances” NextGenerationEU Fund
Subject
Plant Science,Health Professions (miscellaneous),Health (social science),Microbiology,Food Science
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