幼猫源约氏乳杆菌S20分离鉴定及其体外益生作用OA

[Objective]To isolate and identify Lactobacillus johnsonii with favorable probiotic properties from the feces of healthy juvenile Chinese rural cats,systematically evaluate its in vitro probiotic functions,and provide a theoretical basis for the research and development of feline-derived probiotic preparations and their application in the field of nutrition.[Method]Strains were isolated from the feces of healthy juvenile Chinese rural cats using MRS medium and strain identification was conducted via morphological observation,physiological and biochemical tests,combined with 16S rRNA gene sequence analysis.The growth performance and acid-producing capacity of the target strain were assessed by monitoring its growth curves and pH changes.The plate counting method was applied to detect the strain's tolerance to low pH,0.3％bile salt and artificial gastrointestinal fluid.The Oxford cup method was adopted to determine its antibacterial activity against pathogenic bacteria including Escherichia coli,Salmonella and Staphylococcus aureus.Its adhesion potential was evaluated through auto-aggregation rate and surface hydrophobicity assays.Its antioxidant activity was measured by hydroxyl radical and DPPH free radical scavenging tests.Furthermore,its biosafety and antibiotic susceptibility were evaluated via hemolysis test and Kirby-Bauer(K-B)disk diffusion method.[Result]One strain of Lactobacillus johnsonii was successfully isolated and identified.The isolated strain formed white,irregularly edged circular colonies on MRS agar plates and was positive for Gram staining.The isolated strains could utilize glucose,galactose,maltose,sucrose and fructose,but cannot utilize lactose,rhamnose and arabinose.The sequence similarity between the isolated strain and Lactobacillus johnsonii CIP 103620 was over 99％.Therefore,the isolated strain was named Lactobacillus johnsonii S20.Lactobacillus johnsonii S20 grew rapidly and entered the logarithmic growth phase after 2 hours of incubation,with strong acid-producing capacity,the pH decreased to 3.59 after 48 hours of culture.Lactobacillus johnsonii S20 showed excellent stress resistance,with survival rates of 83.72％,86.32％,72.02％and 85.95％under pH 2.0 condition,in 0.3％bile salt,artificial gastric juice and artificial intestinal juice,respectively.Lactobacillus johnsonii S20 exerted significant inhibitory effects on multiple pathogenic bacteria,among which the strongest effect was observed against Escherichia coli,with an inhibition zone diameter of 26.02 mm.In addition,Lactobacillus johnsonii S20 presented favorable intestinal adhesion potential(auto-aggregation rate:83.15％,surface hydrophobicity:67.67％)and antioxidant activity(hydroxyl radical scavenging rate:73.38％,DPPH scavenging rate:34.79％).Safety evaluation indicated that Lactobacillus johnsonii S20 was sensitive to commonly used antibiotics such as penicillin,cephalosporins and chloramphenicol,resistant to partial aminoglycoside and quinolone agents,and exhibited no hemolytic activity.[Conclusion]Lactobacillus johnsonii S20 possessed favorable in vitro probiotic properties and safety,making it a promising candidate strain of feline probiotics with high development potential.