Immunostimulatory and antibacterial activity of Leuconostoc mesenteroides and its purified exopolysaccharide against extended-spectrum beta-lactamase producing Burkholderia cepacia
Authors: Mahdi Likaa H. , Hussein Nadheema H. , Taha Buthainah M. , Auda Ibtesam G. , Zwain Luma A.H. , Mater Haifa N. 
Published: May 2019

Lactic acid bacteria (LAB) have reported as antifungal, antibacterial, and immunostimulatory agents. Exopolysaccharide (EPS) of lactic acid bacteria effectively could stimulate the production of cytokines by macrophages. This study was aimed to extract, purified, and characterize the EPS from Leuconostoc mesenteroides subsp. Cremoris and to evaluate the immunostimulatory and antibacterial activities of EPS against extended-spectrum beta-lactamase (ESBL) producing Burkholderia cepacia strains. Nine EPSs producing L. mesenteroides subsp. cremoris strains were isolated from local dairy products and the isolated bacteria were identified by using API 50. Eight B. cepacia strains were isolated from different specimens in the hospitals of Medical city, Baghdad. Furthermore, genotypic and phenotypic detection of antibiotic resistance were determined including ESBL genes. EPS of L. mesenteroides subsp. Cremoris was extracted and purified by gel filtration chromatography. EPS physical and chemical analysis were performed to characterize it. Antibacterial and immunomodulatory effect of EPS were studied in vivo using mice and ELISA was used to determine the levels of IL-10 in the mice sera. The extracted EPS was found to have a maximum relative viscosity in water (3.51 dl/g) and maximum specific viscosity (2.93 dl/g), while the intrinsic viscosity recorded 1.41 dl/g. The chemical analysis of the extracted polysaccharide was found to contain the following components, carbohydrates, protein, uronic acids, hexosamines, acetyl groups, ketal linked pyruvate groups, phosphate groups, and sulfate groups, also show the following functional groups under infrared (IR) spectra (hydroxyl, alkanes, carbonyl, carbonyl of carboxylic acid, phosphates, and aliphatic amines). HPLC analysis revealed the presence of mannose as a major component with a calculated molecular weight of 1.71 × 103 g/mol. Genotypic detection of the blaPER-1 gene among ESBL producing B. cepacia strains showed the presence of blaPER-1 gene in three (42.86%) strains. Furthermore, to confirm the biological potential, the EPS was evaluated for its antibacterial activity against multidrug resistance B. cepacia strains in vitro and the result showed that the purified EPS was more effective than crude EPS in all concentrations. The protective activities of L. mesenteroides and EPS were observed when administered 7 days before and after B. cepacia infection, whereas therapeutic activities were monitored by administering EPS for 7 days after B. cepacia induction. This results revealed that the administration of L. mesenteroides and EPS significantly decreased the number of B. cepacia in liver, spleen, and lung (P < 0.05). Furthermore, they enhanced production of IL-10. In conclusion, the L. mesenteroides and its EPSs possess antibacterial and immunostimulator properties and are nontoxic with medicinal importance. Therefore, further studies in human participants should determin the role of L. mesenteroides and its EPS as an immunomodulatory and its relationship in the host protection to pathogens.