To the Editor:-As the manufacturer of Betadine Solution (10% povidone-iodine; Purdue Frederick Company), we read the article entitled “Povidone-iodine and skin disinfection before initiation of epidural anesthesia”with great interest.
The authors state that their study shows that multiple-use bottles of povidone-iodine (PI) solution “in normal use may become contaminated by bacteria,” and secondly, that “PI solution from previously opened bottles was less effective than PI from previously unopened bottles.”
A great number of variables important to the issue of possible contamination of the bottle caps (e.g., length and number of times a bottle was left open, technique for handling and storing the cap during opening, protection of opened containers from the environment and from contamination by personnel) are not specified. All of these should have been identified and controlled for in this study to arrive at the conclusions noted with a reasonable degree of certainty.
In the results section of the paper, the microorganisms grown from swabs of the caps from the previously opened bottles and from the solution in the previously opened bottles are listed together in the text. The authors do not provide a Table totell us which microorganisms were found in the caps from opened bottles and which microorganisms were found in the PI solutions. Other than Bacillus, the organisms listed will not survive in PI for more than 15 s. Bacillus (vegetative organisms) have been shown to survive for no more than 30 s in in vitro tests with Betadine Solution. 
Showing that microorganisms commonly found on the skin [4,5]may be present on some caps of previously opened PI bottles demonstrates that caps may become contaminated if not properly handled during use. The study does not demonstrate that microorganisms on the caps contaminate and multiply in the PI solution itself in previously opened PI bottles.
Support of Microbial Growth
In the article, there appears to be confusion between microbial contamination and support of growth. To demonstrate support of growth, colonies of bacteria should be cultured, then reintroduced into the PI solution in a challenge test to determine organism viability. In the absence of these data one must consider that the study results do not demonstrate the support of growth.
The results of the microbial comparison between the third swab used on the patient's back and the PI bottle used for preparing that surface show that, with one exception, the bacteria isolated from the third swab are not the same as the bacteria isolated from the cap or bottle of povidone-iodine used. This suggests that bacterial contamination of the swab is from environmental sources other than the bottle of povidone-iodine used. The authors apparently did not test the new sponge sticks used to sample patients' backs to see whether they may have already been contaminated with Bacillus or Staphylococcus. This would have been an important methodological control.
Although these results might be statistically significant, they are not clinically significant, as demonstrated by the authors' clinical experience. In addition, the reported widespread prevalence of Bacillus may require explanation. Although it is true that bacteria are commonly found on the some parts of the skin, they are not commonly found in large numbers on the skin of the back. There is no adequate explanation for the presence of Bacillus in the setting described in the study.
Loss of Efficacy of PI Solution from Previously Opened Bottles
It is difficult to comment about the reported difference in efficacy between solution from newly opened bottles and solution from previously opened bottles. For opened bottles, the handling technique, the number of openings, and the duration of time of openings should have been recorded and controlled. Also of importance would be the storage conditions of the bottles.
Although the authors raise concerns important to the practice of medicine and to patient health and safety, the results and the conclusions based on them are questionable because of the flawed experimental design. In reality, the study demonstrates that exposed materials may acquire small numbers of organisms from the environment because of less-than-ideal handling techniques. Multiple-use containers of povidone-iodine should be handled in a fashion that minimizes potential contamination. If the clinical-use situation is such that adequate procedures cannot be adhered to, then single-use dosage products (including Betadine Gauze Pads, Betadine Swabsticks, Betadine Swabaids) may be used.
Janet S. Welch, Ph.D.
Director; Medical Services and Drug Surveillance; Purdue Frederick Company; Norwalk, Connecticut
(Accepted for publication August 31, 1998.)