1184 infection control & hospital epidemiology october 2017, vol. 38, no. 10


determine the recovered inocula on the surface as opposed to the applied inocula. Subsequent comparisons in terms of reduced bacterial numbers after plasma exposure were compared to the recovered inocula, not the applied inocula. Statistical analyses were performed using GraphPad Prism 5.00 software (GraphPad, La Jolla, CA). The means of the log values (CFU/mL) from comparisons between recovered control and plasma-treated samples and between samples with and with- out HSA over 15, 20, 30, and 45 seconds were determined using 1-way analysis of variance (ANOVA).


Atomic Force Microscopy


Atomic force microscopy (AFM) images of control (non– plasma-treated) and plasma-treated bacteria were completed in ambient air with a Dimension 3100 AFM microscope con- trolled by a Nanoscope IIIa controller (Digital Instruments, Santa Barbara, CA). This equipment was operated in tapping mode using standard silicon cantilevers (Budget Sensors, Nanoworld Holding, Shaffhaussen, Switzerland) with a 7-nm tip radius and a 42-N/m spring constant (nominal values) to assess the physical effects of the plasma on the bacterial cells. Multiple images were examined and edited using WxSM software (Nanotec Electronica, Madrid, Spain) to generate topography, phase, and profile data.12


results


The effects of the multijet CAPP on A. baumannii, ESBLEC, MRSA, and VRE in the absence and presence of HSA on mattress and stainless-steel surfaces are summarized in Table 1 and are illustrated in Figure 2. The bactericidal effect of the multijet CAPP varied depending on the type of surface, microorganism, and the presence or absence of protein. The most significant effects were observed at the longest exposure time of 45 seconds in the absence of HSA. On the mattress, a 45-second exposure time significantly reduced the bacterial load by approximately log10 3 for A. baumannii (log10 2.92; P<.05) and approximately log10 4 for ESBLEC (log10 4.29), MRSA (log10 4.14), and VRE (log10 3.83). On stainless steel, treatment for 45 seconds reduced the bacterial load of A. baumannii by log10 3.16, ESBLEC by log10 4.69, MRSA by log10 6.21, and VRE by log10 4.36. The addition of protein slightly reduced the efficacy of multijet CAPP, but this reduction was only significant for A. baumannii on the mattress and for VRE on both surfaces (P<.05). The morphological impact of multijet CAPP was evaluated


using AFM. Figure 3a and 3b illustrates untreated MRSA cells. Figure 3a shows a 2D image of the cells. Cells are regular, uniform, and intact, as shown by the 3D image in Figure 3b. However, Figure 3c and 3d illustrates MRSA cells following exposure to the multijet CAPP. The arrows in Figure 3d highlight cells that appear to be depressed, flattened, and deformed, possibly due to cell-membrane disruption and the leaking of cytoplasmic material, which strongly suggests that


table 1. Bacterial Log10 Reduction (CFU/mL)±SEM (n ≥ 3) Following 45 Seconds of Treatment with the Multijet Plasma System in the Absence and Presence of Human Serum Albumin (HSA)


− Surface


Protein (HSA) A. baumannii ESBL E. coli MRSA VRE


Mattress + Stainless Steel − +


2.92±0.15 1.96±0.65 3.16±0.37 2.52±0.73 4.29±0.00 2.33±0.81 4.69±0.00 2.68±0.58 4.14±0.79 1.34±0.22 6.21±0.78 3.73±0.47 3.83±0.09 0.94±0.29 4.36±0.58 2.42±0.22


NOTE. CFU, colony-forming units; SEM, standard error of the mean; ESBL, extended-spectrum β-lactamase–producing; MRSA, methicillin-resistant Staphylococcus aureus; VRE, vancomycin- resistant enterococci.


the multijet CAPP physically disrupts the cells. These effects can also be seen in the AFM images of ESBLEC. Figure 4a and 4b illustrates untreated E. coli cells. The cells can be clearly identified in the image as structurally intact, uniform, and characteristically rod shaped. However, in Figure 4c and 4d, the E. coli cells, following treatment, are swollen and distorted (see arrows). These conditions further suggest that CAPP may induce structural instability in the bacterial cells.


discussion


The inanimate environment in acute-care hospitals may become heavily contaminated with pathogens of HCAIs and may act as a reservoir for transmission. This condition may arise (1) via direct contact by the patient with that surface or item of equipment, (2) via the hands of healthcare workers, hospital visitors, or others touching that surface and then the patient, or (3) via air.13 The pathogens implicated include MRSA, VRE, norovirus, C. difficile, and some gram-negative bacteria. Even with general cleaning or disinfection, residual contamination may remain. For example, approximately 25% of rooms were positive for MRSA despite 4 rounds of cleaning and disinfection in a study of terminal cleaning in a 900-bed community hospital.14 In 2014, Rutala and Weber15 reviewed the qualities of an


ideal disinfectant: fast acting, nontoxic, easy to use, and eco- nomical. Decontamination is often suboptimal because many chemical disinfectants are compromised by their impact on surfaces or by the necessity for vigorous application and because cleaning staff may not be well trained or highly motivated. Enhancing decontamination through the use of HP, UVL, or the incorporation of metals such as copper on surfaces have their limitations, including the need to vacate patients from an area while being disinfected and/or the long- term efficacy of a substance incorporated into a surface.7,8,16 Cold-air plasma (ie, with minimal thermal effects on sur-


faces or equipment) is an alternative to these approaches and works through the production of reactive oxygen species with antimicrobial activity.17,18 Fridman et al19 (2007) demon- strated the efficacy of cold-air plasma on a variety of bacteria


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124  |  Page 125  |  Page 126  |  Page 127  |  Page 128  |  Page 129  |  Page 130  |  Page 131  |  Page 132  |  Page 133  |  Page 134  |  Page 135  |  Page 136  |  Page 137  |  Page 138  |  Page 139  |  Page 140  |  Page 141  |  Page 142  |  Page 143  |  Page 144