Healthcare Hygiene magazine October 2019 | Page 32

A Carrier Platform to Test Microbial Decontamination of High-Touch Environmental Surfaces by Wiping Figure 1: Stainless steel disks embedded in the contaminated and transfer Teflon platforms being wiped. By Syed A. Sattar, PhD; Bahram Zargar, PhD; and Saeideh Naderi, PhD Introduction H igh-touch environmental surfaces (HITES) can spread pathogens in healthcare and other settings (Carling 2016, Weber et al., 2013), and wiping is crucial for HITES decontamination except with no-touch technologies. However, routine decontamination by wiping remains suboptimal (Carling 2016; Sattar and Maillard 2013) and may spread pathogens over a wider area (Ramm et al. 2015). In addition, methods for pre-market testing of environmental surface disinfectants are either qualitative or devoid of any wiping action (Sattar 2010). We report here a quantitative and ‘dynamic’ (combining the physical and chemical action of wipes) test protocol to better reflect the field use of disinfecting wipes. Materials and Methods Acinetobacter baumannii (ATCC 19606), a common healthcare-associated pathogen (Howard et al., 2012), was used for the testing. Trypticase soy broth (TSB) and Trypticase soy agar (TSA) were used, respectively, to grow (20±2 h) and recover (48±2 h) it from the test and control samples at 36±1°C. A Teflon-based platform with perforations (see Figure 1; 30.0 cm x 60.0 cm x 0.5 cm) held nine sterile disks (1 cm in diam.) of brushed stainless steel (AISI 430) as archetypical hard, non-porous HITES. The platform was sterilized by autoclaving. Each sterile disk on one platform received 10 µL of the microbial suspension in a soil load (Sattar et al. 2007) and the inoculum dried. To maintain a uniform pressure during wiping, the operator first practiced the wiping with the platform placed on a digital read-out scale. The platform was then wiped with either Product A (2,600 ppm quaternary ammonium compound; (QAC) or Product B (250 ppm sodium hypochlorite (SH) at neutral pH; Product C, the control, was a microbicide-free fabric (J-Cloth; E.D. Smith Foods, Ltd.) dampened with normal saline with a detergent (0.1% polysorbate-80). The used wipe was immediately applied on another platform with clean disks to assess transfer of any viable organisms. 32 A custom-built retriever simultaneous collected the disks from a given platform into separate vials with 10 mL of an eluent/neutralizer in each. The eluates were individually membrane-filtered (0.22 µm pore diam.) and each filter placed on a TSA plate to recover colony-forming units (CFU) and calculate log10 reductions. Each type of wipe was tested three times under ambient conditions (RH at 45±5%; air temp. 22±2°C). After wiping, the platforms were left undisturbed for 5 minutes. Results As shown in Table 1, Product A reduced the contamination by >4 log10 (>99.99%) with virtu- ally no detectable transfer of CFU to clean disks. CLICK HERE FOR This suggested that the contamination was either Table 1 inactivated or sequestered in the applicator itself. Product B achieved a >2 log10 (>99.00%) reduction in the viability of the test microbe while transferring a higher level of CFUs as compared to Product A. Product C (J-Cloth) achieved <1 log10 (<86.2%) reduction in the test microbe’s viability while transferring >1% of the contamination. In this instance, the reduction in the level of viability was entirely due to mechanical removal of the contamination. The level of transfer from the control fabric was also higher due to the absence of any microbicidal activity. The concentration of SH (neutral pH) in this study was kept deliberately low to enhance workplace safety while also reducing the chemical loading of the environment. Higher levels of SH would most likely perform as well as the QAC-based wipe. Discussion QACs and SH continue to be among the most common microbicides in HITES wipes. However, their respective concentrations in prewetted wipes can vary widely along with the nature of the applicator itself. In the case of the SH-based wipe tested in this study, the fabric was a microfiber cloth as supplied by the wipe manufacturer. The results showed the ability of the platform to assess HITES decontamination as well as the ability of the used wipes october 2019 • www.healthcarehygienemagazine.com