Radioimmunoassay of iodinated tobramycin

A radioimmunoassay for tobramycin was developed using antisera from rabbits injected with a tobramycin-bovine serum albumin conjugate. The antibody had a relatively high affinity for (125)I-labeled tobramycin (1.6 x 10(9) liters/mol), thus indicating little interference in immunoreactivity by iodination. The radioimmunoassay was highly specific, and only minor cross-reaction occurred with other aminoglycoside antibiotics. The radioimmunoassay was also more sensitive than previously published tobramycin assays (minimum sensitivity, 280 pg), and there was a significant correlation (P < 0.05) with both the radioenzymatic and microbiological assays.