Lactic acid bacteria play increasingly important roles in the food industry. Streptococcus thermophilus KLDS 3.1003 strain was isolated from traditional yogurt in Inner Mongolia, China. It has shown high antimicrobial activity against selected foodborne and vaginal pathogens. In this study, we investigated and analyzed its complete genome sequence. The S. thermophilus KLDS 3.1003 genome comprise of a 1,899,956 bp chromosome with a G+C content of 38.92%, 1,995 genes, and 6 rRNAs. With the exception of S. thermophilus M17TZA496, S. thermophilus KLDS 3.1003 has more tRNAs (amino acid coding genes) compared to some S. thermophilus strains available on the National Centre for Biotechnology Information database. MG-RAST annotation showed that this strain has 317 subsystems with most genes associated with amino acid and carbohydrate metabolism. This strain also has a unique EPS gene cluster containing 23 genes, and may be a mixed dairy starter culture. This information provides more insight into the molecular basis of its potentials for further applications in the dairy and allied industries.

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Foodborne pathogens are a major source of morbidity and mortality worldwide. For this cause, exploring various effective ways of suppressing their spread is at the forefront of many research projects. The current study aims to investigate the in vitro organic acid production of S. thermophilus KLDS 3.1003 and L. bulgaricus KLDS 1.0207 strains, their in vivo suppression of and immuno-modulatory effects against E. coli ATCC 25922 and S. aureus ATCC 25923 pathogens. First, lactic and acetic acid production using three carbon sources – 1% glucose (control), 1% sucrose, and 1% fructo-oligosaccharides (FOS) – was determined by HPLC. For the in vivo section, a total of 40 BALB/c mice were purchased and divided into 10 treatment groups (control and nine treatments). Animals were given 1 week to acclimatize and then fed treatment diets for 14 days. Afterward, hematological (RBC, WBC, HB, PLT, Neutrophils, Eosinophils, Lymphocytes, and Monocytes) and histopathological analyses were carried out. All analyses were done in triplicate. Results show that lactic and acetic acid productions for both strains increased with supplementation and were highest after 1% FOS addition. Regardless of carbon source, L. bulgaricus KLDS 1.0207 produced higher ( P < 0.05) amounts of lactic and acetic acids than S. thermophilus KLDS 3.1003. Also, generally better hematological parameters in probiotic groups than the control ( P < 0.05) were observed. In some instances, mice in probiotic treatment groups had better immunity levels (lymphocytes, monocytes, neutrophils, eosinophils) than those in the control and pathogen groups. Histopathological studies showed that no anomalies were associated with S. thermophilus KLDS 3.1003 and L. bulgaricus KLDS 1.0207 administration. In conclusion, S. thermophilus KLDS 3.1003 and L. bulgaricus KLDS 1.0207 strains are not only probiotic candidates but can have therapeutic applications.

Cumulative studies have suggested that probiotic bacteria strains could be an effective alternative in inhibiting conditions caused by foodborne and vaginal pathogens. The use of genomic techniques is becoming highly...