Isolation and Identification of 3 Lactic Acid Bacteria and Their Antibacterial Activity against Klebsiella pneumoniae Isolated from Bovine Mastitis
To obtain lactic acid bacteria(LAB)with potent antibacterial activity against Klebsiella pneumoniae isolated from bovine mastitis,samples including feed,bedding,and milking equipment(6 each)as well as oral cavity,faeces,hoof,teat skin,teat orifice,and nasal cavity swabs(12 each)were collected from a large dairy farm in Shandong Province.Bacteria were isolated and cultured on MRS agar,identified by morphological observation and 16S rRNA gene sequencing,and screened for inhibitory effects on Klebsiella pneumoniae using the Oxford cup method.The antibacterial substances produced by LAB(organic acids,bacteriocins,and hydrogen peroxide)were analyzed,growth curves were established,and antibiotic sensitivity was tested.The results showed that a total of 93 LAB strains were isolated from 90 samples,classified into Weissella(58 strains),Leuconostoc(11 strains),Lactobacillus(17 strains),and Lactococcus(7 strains).Three strains demonstrated significant antibacterial activity against Klebsiella pneumoniae with inhibition zone diameters greater than 17 mm:Weissella cibaria SDS2.1(17.1 mm±1.2 mm),Lactiplantibacillus plantarum SDN1.2(19.73 mm±0.93 mm),and Lactobacillus curvatus SDN6.1(19.53 mm±0.15 mm).Growth curve analysis revealed that all three LAB strains entered the lag phase at 0-2 h,with Weissella cibaria SDS2.1 and Lactobacillus curvatus SDN6.1 entering the logarithmic growth phase at 4-8 h and the stationary phase after 12 h.Lactiplantibacillus plantarum SDN1.2 exhibited a longer logarithmic phase(4-10 h)and entered the stationary phase at 14 h.The main antibacterial substance produced by these strains was organic acids.All three strains were sensitive to 13 common antibiotics,including penicillin,ampicillin,and carbenicillin.The findings indicate that the three LAB strains possess effective antibacterial activity against Klebsiella pneumoniae associated with bovine mastitis and could serve as potential candidates for the prevention and treatment of Klebsiella pneumoniae-induced bovine mastitis.
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