title: An improved method for determining the microbial inhibitory activity of serum and its application to the study of patients with leukemia.
abstract: Numerous investigators have demonstrated that derangements in serum transferrin and iron can contribute to susceptibility to infection, but the complexity and imprecision of assays have impeded both research and development of clinical testing in this area. This article describes an automated assay for measuring the microbial inhibitory activity of transferrin in serum and its use in patients with acute myelogenous leukemia (AML) and in normal controls. The assay measured the ability of heat-inactivated serum to inhibit the growth of an antibiotic-resistant strain of Pseudomonas aeruginosa. The serum dilutions were prepared in a special low iron chemically defined broth. An inhibition index, the reciprocal of the serum dilution producing 50% inhibition of bacterial growth when compared with the growth in broth alone, was determined. The results showed the serum from the patients with leukemia had a significantly lower inhibition index than that of controls (16 +/- 11 vs. 35 +/- 13, P less than 0.01). In addition, they had higher serum iron levels (162 +/- 65 vs. 75 +/- 27, P less than 0.01), lower serum transferrin levels (231 +/- 65 vs. 309 +/- 71, P less than 0.01), and higher percentage saturation of transferrin with iron (59 +/- 21 vs. 20 +/- 8, P less than 0.01) than did controls. Because the assay uses equipment available in many clinical laboratories, it could be developed for routine use as an index of susceptibility to infection in selected patients.
authors.affiliation: Department of Pathology, Emory University School of Medicine, Atlanta, Georgia.
authors.forename: M L
authors.initials: ML
authors.lastname: Towns
authors.forename: B
authors.initials: B
authors.lastname: Bennett
authors.forename: I J
authors.initials: IJ
authors.lastname: Check
authors.forename: R L
authors.initials: RL
authors.lastname: Hunter
mesh_terms: D001770:Blood Bactericidal Activity; D004198:Disease Susceptibility; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007501:Iron / Q000097:blood*; D015479:Leukemia, Myelomonocytic, Acute / Q000097:blood* / Q000382:microbiology; D008297:Male; D008826:Microbial Sensitivity Tests / Q000379:methods*; D011550:Pseudomonas aeruginosa / Q000254:growth & development; D014168:Transferrin / Q000378:metabolism*
chemical_list: D014168:Transferrin; D007501:Iron