Use of the dynamic gastro-intestinal model TIM to explore the survival of the yogurt bacterium Streptococcus thermophilus and the metabolic activities induced in the simulated human gut.

Streptococcus thermophilus, a lactic acid bacterium used to produce yogurts and cheeses is more and more considered for its potential probiotic properties. This implies that additional information should be obtained regarding its survival and metabolic activity in the human Gastro-Intestinal Tract (GIT). In this study, we screened 30 S. thermophilus strains for urease, small heat shock protein, and amino-acid decarboxylase functions which may play a role in survival in the upper part of the GIT. The survival kinetics of 4 strains was investigated using the TIM, a physiologically relevant in vitro dynamic gastric and small intestinal model. The three strains LMD9, PB18O and EBLST20 showed significantly higher survival than CNRZ21 in all digestive compartments of the TIM, which may be related to the presence of urease and heat shock protein functions. When LMD9 bacterial cells were delivered in a fermented milk formula, a significant improvement of survival in the TIM was observed compared to non-fermented milk. With the RIVET (Recombinase In Vivo Expression Technology) method applied to the LMD9 strain, a promoter located upstream of hisS, responsible for the histidyl-transfer RNA synthesis, was found to be specifically activated in the artificial stomach. The data generated on S. thermophilus survival and its adaptation capacities to the digestive tract are essential to establish a list of biomarkers useful for the selection of probiotic strains.

Lactobacillus species signature in association with term and preterm births from low-income group of Pakistan.

AIM/PURPOSE OF STUDY: It is estimated that around 15 million babies are born prematurely every year and approximately one million children die each year due to complications of preterm birth (PTB). Many survivors face a lifetime of disability, including learning disabilities and visual and hearing problems. The current study aimed to characterize Lactobacillus species isolated from vaginal swabs and determine their antibiotic susceptibility. MATERIAL AND METHODS: 40 term and 20 preterm samples were processed by culturing on MRS agar and initial identification was carried out using sugar fermentation reactions and 16S rRNA PCR. Moreover, Lactobacillus species from preterm and term cases using paired samples, i.e. vaginal swabs and placenta tissues from 8 preterm delivering mothers were further recruited for metagenomics study to possibly detect uncultured Lactobacillus species known to cause PTB. RESULTS: 40% samples from preterm delivering mothers lack any Lactobacillus species whereas in contrast vaginal microflora of all term delivering mothers carry one or more species of Lactobacillus. L. crispatus (46% in term group and 25% preterm group) was found to be the most abundant group followed by L. jensenii (25% in both groups) and L. gasseri (19% in term group and 10% in preterm group). The antimicrobial susceptibility profile suggests that preterm isolates were least resistant to linezolid (20% resistance rate) and trimethoprim/sulfamethoxazole (22% resistant rate) compared to term isolates (>60% for each drug group). Furthermore, the metagenomics data for paired samples (8 VS and 8 PT) from extreme PTB suggested that Lactobacillus Iners was the main difference between term and preterm deliveries. Moreover, overall lack of lactobacillus species or presence of rogue Lactobacillus species such as L. iners and L. vaginilis is associated with PTB. ERIC-PCR analysis using Lactobacillus crispatus revealed that all the pre-term samples are closely related and fall in same cluster while all the term samples fall in different cluster. CONCLUSION: The study not only provides a baseline data of distinct signatures of associated lactobacillus species with the PTB which may be further transmitted to new born infants but also developing further therapeutic interventions to better manage the PTB.