Author, as appears in the article.: Torrico, M.; Casino, P.; Lopez, A.; Peiro, S.; Rios, M.; Rios, S.; Montes, M. J.; Guillen, C.; Nardi-Ricart, A.; Garcia-Montoya, E.; Asensio, D.; Marques, A. M.; Pique, N.;

Department: Bioquímica i Biotecnologia

URV's Author/s: Rios Azuara, Santiago

Keywords: Tetrathionate Salmonella detection Mkttn Lyophilizate Improvement Food quality control

Abstract: The detection of Salmonella in food is based on the use of a selective enrichment broth such as Muller-Kauffman Tetrathionate-Novobiocin (MKTTn), in which tetrathionate plays a key role by providing Salmonella with a growth advantage. As sodium tetrathionate is unstable, it is generated in situ by the addition of iodine (Lugol's solution) before seeding. This step is cumbersome as the solution is easily spilled, compromising the performance of the medium and hindering the work of technicians. The aim of this study was to optimize MKTTn broth by generating tetrathionate ex situ through an external reaction between iodine and thiosulphate followed by lyophilization. Quality control procedures were performed to compare the modified and original media, testing pure productivity (enrichment with 50-120 CFU of Sal-monella Thyphimurium ATCC 14028 and Salmonella Enteritidis ATCC 13076 and plating on Xylose Lysine Deoxycholate agar, XLD), mixed productivity (50-120 CFU of Salmonella strains and Pseudomonas aeruginosa and Escherichia coli at & GE;104 CFU and XLD plating) and selectivity (& GE;104 CFU of P. aeruginosa and Enterococcus faecalis and plating on Tryptone Casein Soy agar, TSA). The modified MKTTn medium (S/L) performed comparably with the original medium in terms of growth of both Salmonella strains (> 300 colonies in XLD), alone or with P. aeruginosa and E. coli. Quantitative assays showed no statistically significant differences in the number of colonies grown on XLD after 10-5 dilution (p = 0.7015 with S. Thyphimurium ATCC 14028 and p = 0.2387 with S. Enteritidis ATCC 13076; ANOVA test). MKTTn medium (S/L) was also selective against E. coli (& LE;100 colonies) and E. faecalis (< 10 colonies). These results suggest that adding tetrathionate as a lyophilisate (S/L) is a feasible alternative to the use of Lugol's solution for the preparation of MKTTn enrichment broth and does not affect the properties of the medium.

Thematic Areas: Zootecnia / recursos pesqueiros Saúde coletiva Química Odontología Nutrição Molecular biology Microbiology (medical) Microbiology Medicina veterinaria Medicina ii Medicina i Materiais Interdisciplinar Farmacia Engenharias iii Engenharias i Enfermagem Ciências biológicas iii Ciências biológicas ii Ciências biológicas i Ciências agrárias i Ciência de alimentos Biotecnología Biodiversidade Biochemical research methods

licence for use: https://creativecommons.org/licenses/by/3.0/es/

Author's mail: santiago.rios@urv.cat

Author identifier: 0000-0003-2492-9247

Record's date: 2022-08-20

Papper version: info:eu-repo/semantics/publishedVersion

Link to the original source: https://www.sciencedirect.com/science/article/pii/S0167701222001191

Papper original source: Journal Of Microbiological Methods. 199 106524-

APA: Torrico, M.; Casino, P.; Lopez, A.; Peiro, S.; Rios, M.; Rios, S.; Montes, M. J.; Guillen, C.; Nardi-Ricart, A.; Garcia-Montoya, E.; Asensio, D.; Marq (2022). Improvement of Mueller-Kauffman Tetrathionate-Novobiocin (MKTTn) enrichment medium for the detection of Salmonella enterica by the addition of ex situ-generated tetrathionate. Journal Of Microbiological Methods, 199(), 106524-. DOI: 10.1016/j.mimet.2022.106524

Licence document URL: http://repositori.urv.cat/ca/proteccio-de-dades/

Article's DOI: 10.1016/j.mimet.2022.106524

Entity: Universitat Rovira i Virgili

Journal publication year: 2022

Publication Type: Journal Publications