Turbidimetric determination of blood aminoglycoside levels by growth curve analysis

A procedure to assay rapidly blood aminoglycoside levels was developed based on growth curve analysis of continuous absorbance measurements of a bacterial test strain. Of the means available for monitoring bacterial growth quantitatively, turbidimetric measurement was selected because it can be used to perform a clinical assay in less than 4 hr. Continuous turbidimetric measurements provide information as soon as the antimicrobial agent affects growth, which often occurs within 60 min of the start of an assay. Several bacterial isolates were evaluated before Staphylococcus aureus (MHMC 386) was chosen as the test microorganism. This isolate was quite sensitive to the aminoglycoside antibiotics, permitted the rapid measurement of blood levels of amikacin, gentamicin, kanamycin, and tobramycin, and exhibited a linear dose-response relationship of turbidity over a wide range of antibiotic concentrations.