The effects of X-ray contrast media on bacterial growth

Six widely used X-ray contrast media (XRC) were tested against nine commonly isolated organisms to determine the practicality of using XRC to outline body spaces prior to obtaining specimens for culture and to assess the feasibility of using XRC in divided doses to reduce cost. Preparations of Escherichia coli, Klebsiella pneumoniae, Enterococcus faecalis, Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Candida albicans, Streptococcus pyogenes and Streptococcus milleri in two approximate concentrations of 10(4) and 10(8) colony forming units/mL (cfu/mL) were inoculated into the following XRC: Conray 280, Hexabrix 320, lopamiro 370, Omnipaque 350, Ultravist 300 and Optiray 320 each in two concentrations. Sampling was performed in triplicate at 0, 2, 4 and 20 h with the 20 h counts made after exposure at both 22 degrees C and 4 degrees C. There were 16 significant interactions, predominantly with the Gram-negative organisms. Conray 280 produced the greatest number of effects. Most effects were bacteriostatic. Organisms were most susceptible at low concentration and after prolonged contact with XRC. No effect was seen with dilute XRC. All weekly sterility checks were negative. Non-ionic XRC have no significant effect on the growth of Gram-positive organisms and little effect on Gram-negative organisms if processing is performed promptly. Using standard aseptic technique, no contamination of XRC occurred, suggesting multi-dosing may be a safe and cost-effective method of XRC utilization.