Isolation Characterization and Identification of Lactic Acid Bacteria from Fruit Juices and Their Efficacy against Antibiotics

The presence of lactic acid bacteria (LAB) in dairy products has long been established but the occurrence of this particular group of bacteria in Pakistani fruits has rarely been focused. Therefore, different lactic acid bacteria generally found in fruits, cultivated in Pakistan were studied using microscopic analysis as well as the technique of ribotyping. Following the culture enrichment method randomly selected fruit samples were analyzed. The initial identification was based on conventional morphological and biochemical analysis while the final confirmation was done by utilizing advanced molecular tools (i.e., 16S rRNA gene amplifications). Prior to all these manipulations the growth conditions were carefully optimized for the respective strains. The surveillance of all strains after experiencing an acid shock mimicking the harsh acidic surroundings of gastrointestinal tracts reflects their probiotic potential. The results of antibiotic sensitivity test demonstrated an unusual high rate of kanamycin and oxacillin resistance among isolated LAB strains. Hence it can be hypothesized that use of these antibiotics against pathogens would not disrupt the natural microbiota of gastrointestinal tract which mainly consist of lactic acid bacteria. The study finally led us to conclude that Lactobacillus plantarum was the most abundant type of lactic acid bacteria distributed in most of the fruit samples studied, on the other hand Leuconostoc mesenteroid subsp. mesenteroides showed sporadic occurrence. The presence of such bacteria in raw fruits satisfies the nutritive and microbial profile of fruits to be a healthy food.