A New Bacteriocin from Latilactobacillus sakei: In vitro and In situ Application.

AIMS AND BACKGROUND: Natural preservatives are a viable alternative to replace chemical preservatives that have potential toxicity and carcinogenic effects. OBJECTIVE: To prove the effectiveness in increasing the microbiological stability of Minas Frescal cheese with the addition of a bacteriocin obtained from Latilactobacillus sakei as a natural preservative. METHODS: A new broad-spectrum bacteriocin was evaluated for its functional activity in vitro and in situ when applied in the formulation of Minas Frescal cheese. A commercial bacteriocin was used as a positive control. RESULTS: The inhibitory action of the bacteriocin studied was confirmed, with a reduction of 42.86% in the count of coagulase-positive Staphylococcus in relation to the negative control, at the end of the 30 days of study. For the group of thermotolerant coliforms, the bacteriocin studied showed greater efficiency than the commercial preservative. In vitro analyzes showed the inhibitory action of bacteriocin, above 87% inhibition against S. aureus, E. coli and Salmonela enteritidis, and approximately 90% against Listeria monocytogenes. CONCLUSION: It was concluded that the bacteriocin produced by the Latilactobacillus sakei strain has great potential for application in foods such as Minas Frescal cheese.

Development of Active Packaging Based on Agar-Agar Incorporated with Bacteriocin of Lactobacillus sakei.

In the search for new biodegradable materials and greater microbiological safety and stability of perishable food products, this study aimed to develop a bioplastic antibacterial film incorporating bacteriocin for application in commercial curd cheese and monitoring of microbiological stability. Films with good handling characteristics as well as physical, barrier, and mechanical properties were obtained. Regarding the antibacterial activity, the microbial reduction was demonstrated in a food matrix, obtaining a reduction of 3 logarithmic cycles for the group of coagulase positive staphylococci and from 1100 to <3.00 MPN/g in the analysis of thermotolerant coliforms. Therefore, the film presented food barrier characteristics with the external environment and adequate migration of the antibacterial compound to the product, contributing to the reduction of contamination of a food with high initial microbial load.

Assessment of virulence factors, antibiotic resistance and amino-decarboxylase activity in Enterococcus faecium MXVK29 isolated from Mexican chorizo.

Enterococcus faecium MXVK29 has the ability to produce an antimicrobial compound that belongs to Class IIa of the Klaenhammer classification, and could be used as part of a biopreservation technology through direct inoculation of the strain as a starter or protective culture. However, Enterococcus is considered as an opportunistic pathogen, hence, the purpose of this work was to study the food safety determinants of E. faecium MXVK29. The strain was sensitive to all of the antibiotics tested (penicillin, tetracycline, vancomycin, erythromycin, chloramphenicol, gentamicin, neomycin, kanamycin and netilmicin) and did not demonstrate histamine, cadaverine or putrescine formation. Furthermore, tyrosine-decarboxylase activity was detected by qualitative assays and PCR. Among the virulence factors analysed for the strain, only the genes encoding the sexual pheromone cCF10 precursor lipoprotein (ccf) and cell-wall adhesion (efaAfm ) were amplified. The presence of these genes has low impact on pathogenesis, as there are no other genes encoding for virulence factors, such as aggregation proteins. Therefore, Enterococcus faecium could be employed as part of a bioconservation method, because it does not produce risk factors for consumer's health; in addition, it could be used as part of the hurdle technology in foods. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of molecular techniques has allowed, in recent years, to detect pathogenicity genes present in the genome of starter cultures used in food processing and preservation. The presence of these genes is undesirable, because horizontal transfer may occur with the natural biota of consumers. For this reason, it is important to analyse the presence of pathogenicity genes in such cultures. In this work, virulence factors and antibiotic resistance of Enterococcus faecium strain MXVK29, producing an antimicrobial compound with high antilisterial activity, were analysed. The results indicate that the strain is safe to be used in food processing as starter culture.

Actividad antimicrobiana de Weissella confusa y sus metabolitos frente a Escherichia coli y Klebsiella pneumoniae / Antimicrobial activity of Weisella confusa and its metabolites against Escherichia coli and Klebsiella pneumoniae

Con el fin evaluar el campo de aplicación potencial de una bacteria ácido láctica y de sus metabolitos, se realizó la cinética de la actividad antimicrobiana de W. confusa y de sus metabolitos contra E. coli, y K. pneumoniae, dos patógenos causantes de enfermedades transmitidas por alimentos. La producción de W. confusa se realizó por fermentación discontinua en sustrato comercial MRS. Se realizaron tres fermentaciones durante 6 horas, sin aireación, agitación continúa 33°C y 100 rpm. Cada hora de fermentación se separaron tres sustancias biológicas, W. confusa con sus metabolitos (W+W10b), células de W. confusa libres de metabolitos (W) y metabolito (W10b) y se midió la actividad antimicrobiana contra los patógenos E. coli, y K. pneumoniae. Se encontraron diferencias estadísticas significativas entre tratamientos y tiempo de fermentación. Para E. coli el tratamiento W presentó la mayor actividad antimicrobiana, la cual se obtuvo entre la cuarta y sexta hora de fermentación (2.45 cm de diámetro promedio de inhibición). Para K. pneumoniae, los tratamientos W y W+W10b presentaron actividad antimicrobiana entre la cuarta y quinta hora de fermentación, sin diferencia significativa entre ellos. W. confusa y el metabolito W10b demostraron poseer capacidad antimicrobiana contra E. coli y K. pneumoniae, lo cual sugiere que W. confusa y W10b podrían utilizarse como alternativa de bioconservación o bioprotección de alimentos frescos y procesados, para alimentación humana y animal; y podría convertirse en una alternativa al uso de antibióticos para enfermedades causadas por E. coli y K. pneumoniae.

The kinetic of antimicrobial activity of Weissella confusa and their metabolites against E. coli, and K. pneumoniae, (two pathogens causing foodborne illness) was evaluated, in order to know the possible use in food processing. W. confusa was produced by batch fermentation using MRS commercial substrate. Three fermentations, of 6 hours at 33 °C, without aeration, stirring continuously (100 rpm) were performed. Every hour of fermentation, three biological substances, W. confusa with their metabolites (W + W10b), W. confusa free cells metabolites (W), and metabolite (W10b) were separated, and subsequently the antimicrobial activity against pathogenic E. coli and K. pneumoniae was measured. Statistically significant differences between treatments and fermentation time were found. Treatment (W) against E. coli, showed the greatest antimicrobial activity, it was obtained between the fourth and sixth hours of fermentation (2.45 cm diameter average inhibition). In treatments W and W + W10b against K. pneumoniae, statistically significant differences between them were not found. The antimicrobial activity was shown between the fourth and fifth hour of fermentation. W. confusa and W10b have antimicrobial activity against E. coli and K. pneumoniae, suggesting that W and W10b could be used as an alternative to biopreservation or bioprotection of fresh and processed food for human and animal consumption, and could become an alternative to antibiotics used for diseases caused by E. coli and K. pneumoniae.