[Inhibitory capacity of Lactobacillus spp. against pathogens involved in foodborne diseases]

Applicability of the probiotic Lactiplantibacillus plantarum BFL as an adjunct culture in a dry fermented sausage

The addition of probiotic bacteria to a meat batter allows the development of functional fermented sausages. The aim of this work was to study the effect of microencapsulated Lactiplantibacillus plantarum BFL (EP) and as free cells (FP) on microbiological, physicochemical, and sensory parameters of fermented sausages during the drying stage and on the product ready for consumption. The microencapsulation of L. plantarum BFL did not improve its viability during the drying stage. In addition, sausages inoculated with L. plantarum BFL (FP and EP) caused lower residual nitrites values, pH values and Escherichia coli counts than the Control (C). However, only the presence of free cells of L. plantarum BFL (FP) caused a decrease in the Enterobacteriaceae and mannitol salt-positive Staphylococcus counts. In the sensory analysis, no significant differences were found in the acceptability of the different sausages. However, the acidity in probiotic sausages (FP and EP) was an attribute that consumers highlighted. The probiotic L. plantarum BFL could adapt and survive at high doses in the matrix of an industrial fermented sausage. Therefore, its use could represent a strategy both for biocontrol of pathogens and for the development of functional meat products.

Protective effect of Lactiplantibacillus plantarum LP5 in a murine model of colonisation by Campylobacter coli DSPV458

Thermotolerant Campylobacter species are the leading cause of foodborne bacterial diarrheal disease worldwide. Campylobacter coli, abundant in pigs and pork products, have been identified as a source of human infection. In this study, we propose the use of Lactiplantibacillus plantarum LP5 as a probiotic to reduce colonisation of this intestinal pathogen in a murine colonisation model of C. coli DSPV458. Six-week-old adult female Balb/cCmedc mice were housed in groups: Control, Campy and Pro-Campy. Control and Pro-Campy groups received antibiotics for 5 days and the Campy group for 12 days. Pro-Campy group was inoculated for 7 days with 8.78 log₁₀ cfu total of L. plantarum LP5 suspended in De Man, Rogosa and Sharpe broth. All groups were inoculated with 6.72 log₁₀ cfu of C. coli DSPV458 suspended in brain heart infusion broth. L. plantarum LP5 was recovered only in the Pro- Campy group. C. coli DSPV458 was recovered at higher levels in the Control and Campy groups. The differences with the Pro-Campy group were significant. As regards faeces, Control and Campy groups reached 7.41 and 7.84 log₁₀ cfu/g, respectively, and the Pro-Campy group only 4.62 log₁₀ cfu/g. In the caecum, Control and Campy groups reached 8.01 and 9.26 log₁₀cfu/g, respectively, and the Pro-Campy group only 4.51 log₁₀ cfu/g. In the ileum, Control and Campy groups reached 3.43 and 3.26 log₁₀ cfu/g, respectively, and the Pro-Campy group did not show detectable levels. The reduction of C. coli DSPV458 in the Pro-Campy group compared to the Control group in faeces, caecum and ileum was 99.55, 99.98 and 100%, respectively. Animals were maintained under normal health conditions, and haematological parameters were within the standard values for Balb/cCmedc. The incorporation of a probiotic generated a protective effect in the mice colonisation model. The protective effect would also apply to intestinal colonisation by indigenous enterobacteria. Therefore, the strategy used in this study is of great importance to understand the protection mechanisms in a murine model, as well as its application in food-producing animals.

In vitro screening and in vivo colonization pilot model of Lactobacillus plantarum LP5 and Campylobacter coli DSPV 458 in mice

The objective of this work was to determine the antibacterial effect of Lactobacillus plantarum strains of pork origin against Campylobacter coli strains, and to conduct experimental colonization pilot models in mice for both microorganisms. Inhibition assays allowed evaluation and selection of L. plantarum LP5 as the strain with the highest antagonistic activity against C. coli and with the best potential to be used in in vivo study. Adult 6-week-old female Balb/cCmedc mice were lodged in two groups. The treated group was administered with 9.4 log₁₀CFU/2 times/wk of L. plantarum LP5. L. plantarum LP5 was recovered from the feces and cecum of the inoculated mice. However, when bacteria stopped being administered, probiotic counts decreased. Experimental colonization with C. coli was carried out in five groups of mice. All animals were treated with antibiotics in their drinking water to weaken the indigenous microbiota and to allow colonization of C. coli. Four groups were administered once with different C. coli strains (DSPV458: 8.49 log₁₀CFU; DSPV567: 8.09 log₁₀CFU; DSPV570: 8.46 log₁₀CFU; DSPV541: 8.86 log₁₀CFU, respectively). After 8 h, mice inoculated with different C. coli strains were colonized because the pathogen was detected in their feces. L. plantarum LP5 tolerated the gastrointestinal conditions of murine model without generating adverse effects on the animals. C. coli DSPV458 colonized the mice without causing infection by lodging in their digestive tract, thus generating a reproducible colonization model. Both models combined could be used as protection murine models against pathogens to test alternative control tools to antibiotics.