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.
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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.
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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