Recent confirmation of intrinsic bacterial contamination of 10% povidoneiodine solution has raised questions regarding the bactericidal mechanism of iodophors and the possibility for survival of vegetative bacterial cells in iodophor solutions. In this laboratory investigation, five different species were exposed to various dilutions of three commercial preparations of 10% povidone-iodine solution; survival was assessed after exposure for time periods varying between 0 and 8 min. All brands of povidone-iodine solution tested demonstrated more rapid killing of Staphylococcus aureus and Mycobacterium chelonei at dilutions of 1:2, 1:4, 1:10, 1:50, and 1:100 than did the stock solutions. S. aureus survived a 2-min exposure to full-strength povidone-iodine solution but did not survive a 15-s exposure to a 1:100 dilution of the iodophor. Both stock and dilute preparations of 10% povidone-iodine solution demonstrated rapid bactericidal action against Klebsiella pneumoniae, Pseudomonas cepacia, and Streptococcus mitis.

We investigated the effect ofdisinfectants on microbial contamination present on the interior surface of polyvinyl chloride (PVC) pipes filled with 600 ml of water contaminated with Pseudomonas pickettii and P. aeruginosa. After eight weeks, water was removed, and the test pipes exposed to various types of aqueous disinfectants. Disinfectant samples were removed, neutralized, and examined for recovery of microorganisms by membrane filtration. After seven-days exposure, disinfectant solutions were removed and pipes filled with sterile distilled water. Water was examined by membrane filtration at seven-day intervals to determine whether the organisms had survived in the pipes. Colonization of PVC surfaces were examined during each study phase by scanning electron-

Laboratory investigations were conducted to study potential mechanisms for prolonged survival of Pseudomonas aeruginosa in poloxamer-iodine (PxI). P. aeruginosa organisms isolated from PxI and adapted for growth in distilled water or found as part of a mixed microbial population from water in a manufacturing plant did not survive more than 15 s after challenge in stock PxI solution. Batches of PxI were compounded in the laboratory to determine the survival and growth of P. aeruginosa during the various stages of preparation. No P. aeruginosa organisms were recovered from the finished product at 1 min after the addition of iodine-iodide. However, we found P. aeruginosa in PxI 48 h after adding sterile PxI to the inside of a naturally contaminated polyvinyl chloride water distribution pipe. These organisms (10(4) CFU/ml) survived for as long as 98 days in contaminated stock PxI after it was removed from the polyvinyl chloride pipe. Both decreasing the free iodine level through addition of potassium iodide and increasing the free iodine level through dilution of the product resulted in an increased length of survival of P. aeruginosa in contaminated PxI solution. Comparative survival studies with pipes of different composition revealed that other materials may exert an effect similar to polyvinyl chloride. We concluded that polyvinyl chloride and perhaps other materials may play an important role in the survival of P. aeruginosa in iodophors and may be one source of resistant microbial populations when used in manufacturing plants which produce these antimicrobial solutions.

The intrinsic and extrinsic microbial contamination of large-volume parenterals has been associated with bacteremias in hospitalized patients. When epidemiologic data suggest the association of contaminated intravenous (i.v.) fluids with disease, appropriate laboratory methods must be devised to analyze quickly the suspect fluid. A study was undertaken to compare three laboratory test methods (standard pour plate [SPP] technique, ATP procedure, and Limulus amebocyte lysate [LAL] assay) for detecting the presence of microorganisms in artificially contaminated i.v. fluid. SPP proved the most sensitive of the assay techniques used, but a 24-h period was required for microbial growth. The LAL assay appeared more sensitive in detecting i.v. contamination than the ATP method. These studies suggest that the LAL and ATP methods can be used for the rapid detection of microbial contamination in i.v. fluid. SPP and LAL procedures would have practical laboratory application when the contamination of i.v. fluids is suspected, and they are more sensitive in detecting microbial contamination in these solutions than the ATP method.