METHODS and MATERIALS: - PDF document

METHODS and MATERIALS: Five identical desktop calculators were purchased (Staples SPL - 230, obtained locally) with 1.8 cm 2 keys. Adult volunteer subjects (12 M, 4 F ) were enlisted and each was asked to enter a long key sequence of numbers and operators after the calculator was wiped with an EPA registered disinfecting wipe containing QAC (quaternary ammonia compound, CaviWipes 1, Metrex Research LLC). We instructed them to use their “normal” technique for key entry. The sequence entailed pressing each key a known number of times to comply with the desired sampling plan which totaled 680 keystrokes each. After the sequence was entered, we asked them to use the side of the upper thumb (proximal phalanx) to rub the calculator display in a sideways motion between 4 and 12 times, also randomly assigned, to simulate a high shear interaction. Half the subjects wore nitrile (blue) gloves, the other half were not gloved, prior to key entry. This treatment was randomly determined by having the subjects choose pre - marked forms they could not see from a folder. Subjects were divided into cadres of 5 at different times of the same day. The 16 th subject keyed the sequence separately. Calculators were wiped with a paper towel wet with tap water to remove any residuals between the test cadres. A negative test result was confirmed using the instant chromogenic assay after each cleaning to confirm removal of any residual QAC. Each of the keys and the rubbed display area was tested for the QAC using an experimental chromogenic swab assay after sequence entry (proprietary method ). We also tested the subjects ’ main keying finger pad, as identified by the subject, and the side of the thumb used for rubbing. The assay does not determine the activity of the residual QAC in the product. The wipe solution expressed from the wipes was diluted serially from 1:1 to 1:64 in placebo (Table 2) and swabbed on clean calculator keys in order to determine the sensitivity in this experimental protocol. The placebo is the same as the wipe solution, but contains no QAC’s. Each subject completed a total of 680 keystrokes, or 10,880 keystrokes total for the experiment; no data points were censored . RESULTS: All subjects had to exceed 40 key press cycles ( kpc ) in order to remove 80% of the QAC: the low detection limit of the assay on the keypads (Table 1 and Graph 1). No significant difference in mean kpc to QAC removal between the gloved (nitrile) and skin cadres (75.6 kpc vs. 71.9 kpc ) was found on the keys . We tested the main key finger pad from each subject and were able to detect the QAC on bare skin, but not on the gloved surfaces (87.5 % skin vs 0 % gloved). Rubbing the display area with the thumb , similar results were obtained ( 7 5 % skin, 12.5 % gloved). Combining keystroke and rubbing groups also demonstrated similar results (Table 3 summarizes these results). The experimental instant chromogenic dye test system titered between 1:4 and 1:8 dilution factor on the calculator keys (Table 2). Prior data demonstrated 1:5, or 20% of initial QAC application limit of detection (LOD), on various surfaces. This is consistent with the results on the calculator keys. It takes a lot of keystrokes to remove QAC under this experimental model. The D 50 for 80% QAC removal (~2.8 µ g less) on a calculator key pad was determined to be approximately 74 kpc . Most of the QAC remains on the keys with moderate use. The D 50 is the number of keystrokes at which point half (50%) of the keys would have no detectable QAC by this method. The sample size was too small and too few rub cycles were used to determine how many thumb rubs it took to remove the QAC from the display area . DISCUSSION: Of great interest is why there were no statistically significant differences detected between gloved and not gloved kpc mean values on the key surfaces, and yet a large statistically significant difference was detected between gloved and not gloved finger and thumb surfaces. Where did the QAC go? Subsequent investigations suggested that the QAC may be binding or absorbing into the nitrile glove itself: effectively evading detection by this chromogenic method. This is under continuing investigation. Back calculating from the limit of detection dilution factor, it appears that about 3 to 4 micrograms ( μ g ) of the QAC are deposited on a calculator key. The data indicates that when dry, it takes a lot of handling to bring this level to below detection of the instant chromogenic assay. Considering that one swipe with a wet paper towel removed virtually all of the residual QAC from the keys, the instant chromogenic method is a useful tool to evaluate cleaning compliance of high touch objects (HTO’s) for training, education and compliance auditing. A simple wipe of a towel wet with tap water will prepare an HTO by removing residuals. The HTO can be quickly read at a later time, presumably after use of a disinfecting wipe, to determine if it was wiped with the disinfectant product. The experiment has demonstrated that moderate use of the HTO, such as keying and rubbing, will not corrupt the determination of the thoroughness of disinfection cleaning, or TDC 4,5 score, when evaluating hygienic cleaning in facilities. REFERENCES 1. Hartmann B, et. al ., Computer keyboard and mouse as a reservoir of pathogens in an intensive care unit ., J. Clin Monit Comput . 2004 Feb;18(1):7 - 12 2. Frank, J.F., Chmielewski , R.A ., Effectiveness of sanitation with quaternary ammonium compound or chlorine on stainless steel and other domestic food - preparation surfaces . J. Food Prot . 1997 Jan;60(1):43 - 7 3. Arias, Kathleen, MS, CIC, Contamination and Cross Contamination on Hospital Surfaces and Medical Equipment, Initiatives in Safe Patient Care , Saxe Communications, 2010. (www.initiatives - patient safety.org ) 4. Guh , A., Carling, P., MD., et. al ., Options for Evaluating Environmental Cleaning , CDC, December 2010 5. Carling, P., MD., Methods for assessing the adequacy of practice and improving room disinfection . AJIC 41 (2013 ), S20 – S25 FINANCIAL DISCLOSURE : Authors are employed by Metrex Research, LLC . 1717 W. Collins Ave., Orange, CA, 92867, USA CONCLUSION: It takes a lot of pressing and rubbing by the healthcare workers fingers to remove sufficient QAC to reduce it to 20% or less of the original application from a disinfecting wipe. This study demonstrates that moderate use of the keys between disinfection and cleaning leaves detectable QAC, indicating it is an effective cleaning compliance indicator on high touch objects. BACKGROUND/ OBJECTIVES and SCOPE : The proliferation of electronically controlled medical devices and keyboards used in the healthcare environment has made pressing a button on a keypad a constantly repeated part of every healthcare worker’s shift. The role of these keypads as fomites are well described 1,2,3 . Many of these keypad and keyboard fomite surfaces are cleaned and disinfected on a regular basis. Persistence of various disinfecting compound residuals on surfaces has been described, but little quantitative information exists about the effect of use and handling of these fomites on this persistence : a practical point of consideration for Infection Control Professionals, Toxicologists and medical device designers alike. We set out to answer a few basic questions by having volunteers touch actual keys a known number of times: • How many times can the key be pressed before the residue is substantially removed? • Are gloved hands any different from ungloved hands with respect to the keys and the hand surfaces which touch the keys? Pushing Our Buttons: How Many Cycles Does It Take to Remove An Active Disinfecting Compound From A Keypad ? Steve Burns *, Tim T aylor, Ph.D., Joe Tulpinski, Abhigyan Som, Ph.D. Presented at the Association for Professionals in Infection Control and Epidemiology (APIC) Annual Conference . Anaheim, CA., June 7 - 9, 2014. *: Correspondence: steve.burns@sybrondental.com