Isolation and Identification of Probiotic Microorganisms in the Regions of Northeast Syria

Abstract

Probiotics are defined as live microorganisms that, when given in sufficient amounts, provide health benefits to the host by maintaining intestinal microbial balance. Among these, lactic acid bacteria (LAB), commonly found in milk and dairy products, are the most widely used. Over 100 samples of milk and its derivatives were inoculated onto De Man, Rogosa, and Sharpe (MRS) agar plates and incubated at 37°C for 48 hours under both aerobic and anaerobic conditions. From the aerobic incubation, more than 30 samples were identified as Lactobacillus bacteria using morphological and biochemical assays, including Gram staining and the catalase test. All isolates displayed either cocci or rod-shaped forms, Gram-positive and catalase-negative, confirming their classification as LAB. Finalay, PCR method with specific primers was used to confirm the isolated strains. These 30 LAB isolates were further tested for antimicrobial activity against human pathogens Escherichia coli and Staphylococcus aureus. Seven sample showed broad-spectrum antimicrobial effectiveness. The isolates tolerated acidic conditions within a pH range of 2.0 to 5.0, grew well in the presence of NaCl, and efficiently metabolized lactose. Antibiotic susceptibility testing with Ampicillin, Doxycycline, Ceftriaxone, and Amikacin revealed notable resistance to Ampicillin and Amikacin, while susceptibility was observed for Doxycycline and Ceftriaxone. Based on probiotic characterization and antibiotic resistance patterns, the seven sample were confirmed as promising probiotic LAB strains. 16S rDNA sequence analysis identified them as belonging to Lactobacillus plantarum, L. paracasei, L. casei, L. fermentum, L. rhamnosus, L. reuteri, L. brevis, and L. acidophilus.