In Vitro Phenotypic Screening and MALDI-TOF Identification of Lactic Acid Bacteria Isolated from Feces of Suckling Piglets with Antibacterial Activity

Lactic acid bacteria are important components of the early gut microbiota in piglets and may contribute to gastrointestinal stability and control of enteric pathogens, particularly under increasing restrictions on antibiotic use in livestock production. This study aimed to perform in vitro phenotypic screening and characterization of lactic acid bacteria isolated from feces of suckling piglets aged 7–28 days. A total of 42 fecal samples were collected and cultured on selective media, yielding 318 colonies, of which 135 Gram-positive, rod-shaped, catalase-negative isolates were retained for further evaluation. These isolates were assessed for tolerance to acidic conditions (pH 2.0–3.1), bile salts (0.3–0.5%), cell surface hydrophobicity, hemolytic activity, and antibacterial activ-ity against Escherichia coli and Staphylococcus aureus. Among them, only two isolates (PMvet212 and PMvet318) showed detectable tolerance to acidic and bile conditions and exhibited moderate antibacterial activity, with inhibition zones of approximately 10-12 mm. Identification using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry indicated that PMvet212 was closely related to Lactobacillus brevis, whereas PMvet318 was identified at the genus level as Lactobacillus sp. Both isolates displayed α-hemolytic activity, indicating the need for further safety evaluation. Overall, the findings provide preliminary evidence of selected functional properties of piglet-derived lactic acid bacteria; however, additional molecular characterization and in vivo studies are required before any practical application can be considered.