Rectal Thermocouple Catheters'

MIAHER, J. T. (Quartermaster Research and Engineering Command, Natick, Mass.), M. R. ROGERS, AND D. W. PETERSON. Evaluation of disinfection techniques for, and their effects on, rectal thermocouple catheters. Appl. Microbiol. 9:273-278. 1961.The antibacterial activities of an iodophor (Wescodyne G), a quaternary ammonium compound (Roccal), and an iodine tincture as agents for the cold disinfection of rectal catheters contaminated in vitro were determined. Following thorough cleaning with an alcoholic solution of soft soap, each of the three disinfectants tested showed satisfactory results (100% kill) in 5 min against the enteric test bacteria (Escherichia coli and Salmonella typhosa) as well as a test species of the genus Pseudomonas, among the bacteria most resistant to surface-active agents. An aqueous solution of Wescodyne G containing 75 ppm available iodine was used both as a wiping solution and for subsequent disinfection of rectal catheters contaminated in vivo. Total bacterial destruction was found to follow a 60-min soak preceded by the wiping procedure. Rectal catheters subjected to prolonged immersion in each of the test disinfectants were found to be essentially unaffected, retaining their initial calibrations within a permissible tolerance. Neither Roccal nor Wescodyne G solutions were found to measurably attack bare thermocouples. Alcoholic iodine 0.5% did, however, exert a deteriorating effect on bare thermocouples in a short time, as measured by change in resistance characteristics. The results of this study have led to the recommendation that Wescodyne G containing 75 ppm available iodine be used in standing operating procedures for the initial cleaning and subsequent disinfection of rectal thermocouple catheters. The rectal thermocouple catheter has proved to be an invaluable laboratory and field instrument in gathering physiological data (Mead and Bommarito, l The views and conclusions herein contained are those of the authors. They are not to be construed as necessarily reflecting the views or indorsement of the Department of Defense. 1948; Davidzick, Harvey, and Goddard, 1953). This deep body temperature-sensing device is now worn by resting or active volunteer military test participants with physiological and psychological acceptability even under extreme temperature conditions (+120 to -65 F). Although the results of studies on disinfecting rectal thermometers are available (Gershenfeld, Greene, and Witlin, 1951; Sommermeyer and Frobisher, 1953), there is little or no information about disinfecting rectal catheters. Since there is danger of rectal catheters transmitting infectious agents, and considering their unique structure and function, it is advisable to standardize a technique for disinfecting catheters. This study was begun with two objectives, namely: Phase I. To establish an efficient technique for the disinfection of rectal catheters, and Phase II. To investigate the effects, if any, of disinfectant action on the components of rectal catheters, specifically in regard to functioning and use-life. MATERIALS AND METHODS Phase I. Bacteriological Studies A) Studies in vitro. 1) Rectal thermocouple catheters. The catheters used in this study (Fig. 1) are temperature measuring devices constructed of modified Dow Corning2 9711 silicone rubber covering a 30 gauge copper-constantan thermocouple. The thermocouple is fused with silver solder to a brass tip. The tip is crimped to the end of a 318 by 0.16-in. catheter body. 2) Disinfectants tested. (i) Wescodyne G3 (Federal stock no. 6840-526-1129) solution containing 75 ppm available iodine (4.7 ml of Wescodyne G to 1 liter distilled water). Wescodyne G is a brand of iodophor containing as active ingredients: polyethoxy polypropoxy polyethoxy ethanol-iodine complex, nonylphenoxy polyethoxy ethanol-iodine complex, and hydrogen chloride; (ii) alcoholic iodine solution, 0.5 % (5 g iodine in sufficient 70 % isopropyl alcohol to make the product measure 1 liter); (iii) alcoholic Roccal4 solution, 1-1,000 (10 ml of 10% Roccal to 990 ml of 2 Dow Corning Corporation, Midland, Mich. 3 West Chemical Products, Inc., Long Island City, N. Y. 4 Sterwin Chemicals, Inc., New York 18, N. Y. 273 on S etem er 3, 2017 by gest ht://aem .sm .rg/ D ow nladed fom J. T. MAHER, M. R. ROGERS, AND D. W. PETERSON 70% isopropyl alcohol). Roccal is a brand of alkyldimethylbenzylammonium chloride. The test concentrations of the commercial disinfectants were those recommended by the respective manufacturers. The efficiency ascribed by Sommermeyer and Frobisher (1953) to a 0.5 % alcoholic iodine solution in disinfecting rectal thermometers was the basis for its selection. Isopropyl alcohol was used as the carrier for Roccal since tinctures of the quaternary ammonium compounds have been found to be much more effective than aqueous solutions. Aqueous Zephiran,5 0.1 %, is, in fact, used to isolate Mycobacterium tutberculosis from various body fluids (Patterson, 1956). 3) Test organisms and media. The test organisms used were Escherichia coli ATCC 26, Salmonella typhosa Hopkins strain, and Pseudomonas aeruginosa ATCC 13,388. Stock cultures of E. coli and S. typhosa were carried on slants of Bacto6 stock culture agar, whereas P. aeruginosa was maintained on Sabouraud maltose agar (Davis et al., 1959). These organisms are considered among the bacteria most resistant to surface-active agents (Glassman, 1948). A transfer from the stock culture to 25 ml of BBL' Fluid Thioglycollate medium, followed by three daily subcultures prepared each organism for use. Fluid Thioglycollate was also used to recover each of the test organisms after disinfection. However, this transplant medium for Roccal-subjected catheters contained 3 % Tween 801 and 0.2 % lecithin. Eosin methylene blue agar was used as a confirmatory medium for E. coli from tubes of broth showing growth. Broth cultures suspected to be S. typhosa were subcultured on BBL bismuth sulfite agar. The strain of P. aeruginosa 5 Winthrop Laboratories, New York 18, N. Y. 6 Difco Laboratories, Inc., Detroit 1, Mich. 7 Baltimore Biological Laboratory, Inc., Baltimore, Md. 8 Atlas Powder Co., Wilmington, Del. used produced the characteristic blue-green pigment in abundance, and this was considered an adequate criterion for identification. The bacterial pick-up by lubricated catheters was determined by plate counts using Bacto Tryptone glucose extract agar, recommended for the standard plate count according to Standard Methods for theExamination of Water, Sewage, and Industrial Wastes (APHA, 1955). 4) Wiping solution. An alcoholic solution of soft soap containing 75 g soft soap in 1 liter of 70% isopropyl alcohol. 5) Lubricant. K-Y9 sterile lubricant. A greaseless, water soluble lubricant recommended for easy insertion of rectal thermometers. 6) Temperature. The tests were performed at a range of 29 to 30 C. 7) Techniques. Since frequent sterilization by steam under pressure may adversely affect the properties of rubber, all catheters used throughout the study were subjected to dry heat at 110 C for 30 min. This process effectively destroyed vegetative contaminants without killing contaminating spores. Somewhat limited data, then, could be obtained about the sporicidal activity of the disinfectants. A surface film of the sterile, water-soluble lubricant was applied to the catheters to simulate the condition found to exist upon removal of a catheter from the rectum. After lubrication, the catheters were contaminated by immersing in 25 ml of a 22to 26-hr thioglycolate broth culture of one of the organisms, and then wiped with cotton moistened with the alcoholic solution of soft soap described above. The soap was then removed by rinsing with sterile distilled water, and the catheters transferred to a 600-ml beaker containing enough disinfectant to permit complete im9 Johnson and Johnson, New Brunswick, N. J. FIG. 1. Catheter, thermocouple type I L VO4FILNOR. CANNON 274 [VOL. 9 on S etem er 3, 2017 by gest ht://aem .sm .rg/ D ow nladed fom DISINFECTION OF RECTAL THERMOCOUPLE CATHETERS mersion. After a 5-min immersion in the disinfectant, the catheters were given 2 rinses; first with sterile sodium thiosulfate solution, 1 % to inactivate the iodine carried over from the Wescodyne G and alcoholic iodine solutions, then with sterile distilled water. The catheters were then aseptically transferred by sterile forceps to tubes of culture media. The tubes were incubated at 37 C until growth was visible, or for 3 days if there was no apparent growth. Catheters from tubes showing no growth 3 days after disinfection with Roccal were checked for bacteriostasis by transferring them to other tubes of broth. Such transfers were not considered necessary after iodine activity, since sodium thiosulfate effectively inactivates the antibacterial action of iodine. B) Studies in vivo. A lubricated, nonsterile rectal catheter was inserted into each of ten test subjects. The catheters were worn for a 5-hr period, 1 hr of which included treadmill activity at 3 mph to insure maximal rectal contact. Catheters were removed during this 5-hr contact period only for defecation, when necessary, and reinserted immediately thereafter. Immediately upon removal from the rectum, catheters were wiped thoroughly with cotton moistened with an aqueous'0 solution of Wescodyne G, rather than the alcoholic soap solution used during the studies in vitro." After cleaning and subsequent treatment with aqueous Wescodyne G, the catheters were processed in the same manner as described under A) Studies in vitro. This procedure was repeated for 6 days; the amount of time the catheters were exposed in the disinfectant was the only variable. Catheters worn on the first, second, third, and fourth days were exposed for 5, 10, 30, and 60 min, respectively. When the efficacy of the 60-min exposure became apparent, the catheters worn on the fifth and sixth days were also subjected to the 60-min exposure to enhance the reliability of the results. Phase II. Effect of Disinfectants on Rectal Catheters Three tests were made to determine the possibly harmful effect of test disinfectants on: (i) possible swelling of silicone rubber of the catheter, (ii) the complete or intact catheter, and (iii) the bared silversoldered thermocouple of the catheter. Methods for each of these are described below. A) Resistance of silicone rubber to test disinfectants. 10 Natick tap water was used as the carrier for Wescodyne G, rather than distilled water. 11 Soap will impair the activity of Wescodyne G if inadvertently carried-over into the disinfectant solution. Further, detergent-germicides such as Wescodyne G are expected to clean thoroughly, as well as destroy microorganisms in the presence of variable amounts of organic and inorganic matter. The phenomenon of rubber products swelling in liquids is of practical importance not only because of dimensional changes, but also because of the effect on physical properties. The swelling of a rubber in a liquid is taken as an indication of its resistance, or lack of resistance to a fluid (Wilson, Griffis, and Montermoso, 1958). The method used in determining the percentage of swelling of silicone rubber specimens exposed to each of the test disinfectants conforms to that described in Federal Test Method Standard No. 601 (U. S. Government Printing Office, 1955). B) Effects of exposure of intact rectal catheters to test disinfectants. The first step in evaluating these effects consisted of totally immersing six precalibrated rectal catheters in each of the test disinfectants. After exposure times of 5, 10, 30, 60 min, 24 and 48 hr, catheters were removed and rinsed with tap water. The catheter tips were then fastened with a rubber band to the bulb of a National Bureau of Standards certified mercury thermometer, enclosed in a water-tight polyethylene bag,'2 and immersed in a well stirred water bath. Aftex a more than adequate temperature equilibration period at both 95 and 98 F, the emf of each catheter thermocouple was measured in millivolts with a model 8662 Potentiometer'3 and converted to degrees Fahrenheit. Confirmation of measurements was made with a type K-3 Universal Potentiometer.'3 A series of five readings was made on each catheter at a specific temperature, and a mean reading was recorded. In all tests, a nonexposed, standardized reference thermocouple was used as a control. C) Effects of exposure of bared, silver-soldered thermocouples to test disinfectants. Since it is conceivable, although unlikely, that a disinfectant could penetrate the catheter core (thermocouple) without measurably altering the true emf, it was considered desirable to investigate this possibility. A rectal catheter of proper thermoelectric characteristics was cut apart and sections of copper and constantan wire cut from it were made into thermocouples. The junctions were silversoldered, and care was taken to remove all trace of flux. The free ends of a thermocouple so made were attached to the binding posts of a Wheatstone bridge and the silver-soldered junction immersed in a beaker containing a test disinfectant in such a way that 2 in. of both copper and constantan above the junction were exposed to the disinfectant. Anl initial resistance measurement was made, and subsequent readings were recorded at various intervals throughout a 24-hr