The effect of contrast media on the growth of bacteria.

Some water-soluble radiological contrast agents have been shown to have anti-bacterial activity, a phenomenon which might interfere with bacterial cultures from body fluids containing contrast media. The new low-osmolality contrast media are known to achieve much higher urinary concentrations than their predecessors in intravenous urography, and any anti-bacterial properties they might possess could be especially important in this examination. These agents have been examined with some conventional counterparts for anti-bacterial activity against a range of common pathogens with some positive results. Several parameters which might be thought to play a role in the phenomenon--osmolality, free iodide, pH and the methylglucamine radical--have been examined and eliminated. The bactericidal effect manifested by several contrast agents was found to be eliminated in the presence of urine, dispelling fears for urine cultures following urography, but a theoretical problem still remains in examinations of the biliary tract with some of the media.