title: In vitro growth inhibition of mastitis-causing coliform bacteria by bovine apo-lactoferrin and reversal of inhibition by citrate and high concentrations of apo-lactoferin.
abstract: Bovine apo-lactoferrin (apo-Lf) was added to in vitro cultures of eight strains of coliform bacteria associated with bovine mastitis. As little as 0.02 mg of APO-Lf per ml resulted in marked inhibition of growth of all coliforms. Growth inhibition was lost if saturated Lf or iron plus apo-Lf was added to the synthetic medium. The inhibition of growth increased as the concentration of apo-Lf increased from 0.02 to 0.2 mg/ml for Klebsiella pneumoniae (OARDC-A1), Klebsiella spp. (K1-21), and Aerobacter aerogenes (55-12222) and 2 mg/ml for A. aerogenes (76-2414-1), Escherichia coli (60-Lilly), E. coli (66-S16), and Klebsiella spp. (K6-24). As the concentration of apo-Lf was increased above 0.2 or 2 mg/ml, there was less inhibition of growth except for E. coli (33-C4). Apo-Lf at 20 mg/ml was bactericidal for E. coli (33-C4). Results are compatible with the hypothesis that coliform bacteria respond to low-iron environments by production of iron-sequestering agents that complete effectively with apo-Lf for free iron. Addition of apo-Lf plus citrate resulted in loss of growth inhibition. The molar ratio (citrate to apo-Lf) was found to be more important than the absolute concentration of either component. A ratio of 75 resulted in 50% growth inhibition, whereas ratios of 300 and greater resulted in less than 10% growth inhibition. These results suggest that the ratio of citrate to Lf would be important in evaluating Lf as a nonspecific protective factor of bovine mammary secretions.
mesh_terms: D000818:Animals; D002417:Cattle; D002951:Citrates / Q000494:pharmacology*; D003470:Culture Media; D004305:Dose-Response Relationship, Drug; D004754:Enterobacter / Q000254:growth & development*; D004755:Enterobacteriaceae / Q000254:growth & development*; D004926:Escherichia coli / Q000254:growth & development*; D007501:Iron / Q000378:metabolism; D007711:Klebsiella pneumoniae / Q000254:growth & development*; D007781:Lactoferrin / Q000494:pharmacology*; D007782:Lactoglobulins / Q000494:pharmacology*; D008414:Mastitis, Bovine / Q000209:etiology*
chemical_list: D002951:Citrates; D003470:Culture Media; D007782:Lactoglobulins; D007501:Iron; D007781:Lactoferrin