Abstract
Abstract This study evaluated the critical factors in the titration of penicillin and cephalosporin antibodies using hemagglutination techniques. Emphasis was placed on the development of sensitive and reproducible methods for further investigational work as well as the development of a simple and practical method suitable for use by clinical laboratories with only occasional need for performing such tests. Conditions for optimal sensitization of erythrocytes with the antibiotics were evaluated including concentration of the antibiotics; pH, temperature, and time of sensitization; comparison of red cells from different donors; and the effects of varying conditions of storage and age of the red cells. Optimal sensitization of red cells by penicillin are obtained when 1 ml of fresh erythrocytes is incubated with 1,000,000 units Kbenzylpenicillin G in 15 ml Trimethylamine (TMA)-buffer, pH 10.0, at room temperature for 2 hr. Similarly, for preparation of cephalothin-sensitized red cells, 1 ml of fresh erythrocytes is incubated with 400 mg Na-cephalothin in 10 ml TMA-buffered saline (pH 10.0) at 37°C for 2 hr. Red cells sensitized at pH 10.0 with penicillin gave titers 30 times higher than those sensitized at pH 7.3, but only marginal differences were noted with cephalothin. Several hemagglutination systems were evaluated, including standard blood-banking methods such as saline, albumin and antiglobulin techniques. These were compared with agglutination in a diluent containing dextran, normal rabbit serum, and Tris-buffered saline (Dex-NRS-TBS). The indirect antiglobulin (Coombs') test using antibiotic-sensitized cells is optimal for clinical purposes. However, if numerous penicillin and cephalothin antibody titrations are to be performed for investigational work, direct agglutination in Dex-NRS-TBS is generally more practical.
Published Version
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