Effects of Lactobacillus plantarum and Weissella viridescens on the Gut Microbiota and Serum Metabolites of Mice with Antibiotic-Associated Diarrhea

Antibiotic-associated diarrhea (AAD) refers to diarrhea caused by gut microbiota disorders after the use of antibiotics, which seriously threatens the health of humans and animals. Therefore, it is necessary to find an effective therapy to treat AAD. This research aimed to explore the effects of Lactobacillus plantarum H-6 (L. plantarum H-6) and Weissella viridescens J-1 (W. viridescens J-1) on alleviating antibiotic-associated diarrhea induced by lincomycin hydrochloride (LH) in mice. The results show that L. plantarum H-6 could significantly reduce the expression of pro-inflammatory factors such as IL-1β and IL-6 in colon tissue. At the same time, L. plantarum H-6 significantly increased the abundance of Lactobacillus and Akkermansia, decreased the abundance of Bacteroides, and increased the contents of L-tryptophan, LysoPC (20:4 (8Z, 11Z, 14Z, 17Z)), reduced riboflavin, threoninyl-methionine, and N-palmitoyl in serum. However, W. viridescens J-1 had little effect on the treatment of AAD. It can be concluded that L. plantarum H-6 can regulate mice's colonic microbial composition, improve their serum metabolic process, and alleviate antibiotic-associated diarrhea. This research may provide a novel therapeutic option for AAD.

Selection, truncation and fluorescence polarization based aptasensor for Weissella viridescens detection

Weissella viridescens is a spoilage bacterium commonly found in low-temperature meat products. In this work, after fifteen rounds including three counter selection rounds of whole-cell systemic evolution of ligands by exponential enrichment (SELEX) in vitro, a novel aptamer L3 that can specifically recognize W. viridescens was obtained with a dissociation constant (K_d) value of 68.25 ± 5.32 nM. The sequence of aptamer L3 was optimized by truncation and a new aptamer sequence TL43 was obtained with a lower K_d value of 32.11 ± 3.01 nM. Finally, a simple and rapid fluorescence polarization (FP) platform was constructed to detect W. viridescens, in which FAM-labeled complementary sequence (FAM-cDNA) was employed to generate FP signal and streptavidin was used to amplify FP signal. In the presence of target bacteria, FP value decreased owning to the dissociation of FAM-cDNA from streptavidin/biotin-TL43/FAM-cDNA complex. Under optimal conditions, the concentration of W. viridescens and FP value displayed a good linear relationship with the detection range from 10² to 10⁶ cfu/mL. Moreover, the designed detection system had a good recovery rate of 90.6%-107.7% in smoked ham samples compared with classical plate counting method, indicating the great potential of the selected and truncated aptamer in practical biosensing applications.

A mathematical modeling approach to the quantification of lactic acid bacteria in vacuum-packaged samples of cooked meat: Combining the TaqMan-based quantitative PCR method with the plate-count method

The TaqMan-based quantitative Polymerase Chain Reaction (qPCR) method and the Plate Count (PC) method are both used in combination with primary and secondary mathematical modeling, to describe the growth curves of Leuconostoc mesenteroides and Weissella viridescens in vacuum-packaged meat products during storage under different isothermal conditions. Vacuum-Packaged Morcilla (VPM), a typical cooked blood sausage, is used as a representative meat product, with the aim of improving shelf-life prediction methods for those sorts of meat products. The standard curves constructed by qPCR showed good linearity between the cycle threshold (C_T) and log₁₀ CFU/g, demonstrating the high precision and the reproducible results of the qPCR method. The curves were used for the quantification of L. mesenteroides and W. viridescens in artificially inoculated VPM samples under isothermal storage (5, 8, 13 and 18 °C). Primally, both the qPCR and the PC methods were compared, and a linear regression analysis demonstrated a statistically significant linear correlation between the methods. Secondly, the Baranyi and Roberts model was fitted to the growth curve data to estimate the kinetic parameters of L. mesenteroides and W. viridescens under isothermal conditions, and secondary models were used to establish the dependence of the maximum specific growth rate on the temperature. The results proved that primary and secondary models were adequate for describing the growth curves of both methods in relation to both bacteria. In conclusion, the results of all the experiments proved that the qPCR method in combination with the PC method can be used to construct microbial growth kinetics and that primary and secondary mathematical modeling can be successfully applied to describe the growth of L. mesenteroides and W. viridescens in vacuum-packaged morcilla and, by extension, other cooked meat products with similar characteristics.

A novel real-time PCR assay for the specific identification and quantification of Weissella viridescens in blood sausages

Weissella viridescens has been identified as one of the lactic acid bacteria (LAB) responsible for the spoilage of "morcilla de Burgos". In order to identify and quantify this bacterium in "morcilla de Burgos", a new specific PCR procedure has been developed. The primers and Taqman probe were designed on the basis of a sequence from the gene recN. To confirm the specificity of the primers, 77 strains from the genera Carnobacterium, Enterococcus, Lactobacillus, Leuconostoc, Pediococcus, Streptococcus, Vagococcus and Weissella were tested by conventional PCR. The specificity of the primers and the correct functioning of the probe was confirmed by performing real-time PCR (qPCR) with 21 W. viridescens strains and 27 strains from other LAB genera. The levels of detection and quantification for the qPCR procedure proposed herein were determined for a pure culture of W. viridescens CECT 283(T) and for "morcilla de Burgos" artificially inoculated with this species. The primers were specific for W. viridescens, with only one product of 91 bp being observed for this species. Similarly, the qPCR reactions were found to be specific, amplifying at a mean CT of 15.0±0.4 only for W. viridescens strains. The limit of detection (LOD) and quantification (LOQ) for this procedure was established in 0.082 pg for genomic DNA from W. viridescens. With regard to the artificially inoculated "morcilla", the limit of quantification was established in 80 CFU/reaction and the limit of detection in 8 CFU/reaction. Consequently, the qPCR developed herein can be considered to be a good, fast, simple and accurate tool for the specific detection and quantification of W. viridescens in meat samples.