Microsoft word - sage steam microbiological report

Information and statistics reproduced with permission of copyright holder Page - 2 - of 8 SDV8000 Laboratory trials 2009
1.0 Introduction
Sage Sanitizing Systems Ltd are in the business of providing technological solutions for the sanitization of
Industrial, commercial and medical environments. This report details the results and findings of laboratory
trials relating to the performance of the “Sage Steam” 8 bar steam and vacuum cleaning system. This
system is intended for cleaning flat surfaces.
This device consists of a mobile steam generation unit and waste collection unit to which a tube assembly
is connected through which steam is delivered to a work head and by which a vacuum suction system
removes treated debris from the working environment. Debris is generated during use and is collected in a
waste vessel, which is in tended to be maintained in a sanitary state by the addition of a disinfectant agent.
The objectives of the work reported here were as follows: A) To quantify the antimicrobial performance of this device against a range of medically significant organisms with respect to the cleaning of soiled surfaces. B) To assess the performance of a range of candidate antimicrobial substances with regard to the sanitization of the debris collection vessel. C) To determine the existence and quantify the nature of any undesirable cross contamination events during operation. D) To describe and provide measurement of the temperature dynamics inside and below the work head treatment area during usage Information and statistics reproduced with permission of copyright holder Page - 3 - of 8 SDV8000 Laboratory trials 2009 2.0 Conditions; Flat Surface Cleaning Trials
Assessment of Test Surfaces and Debris reservoir
The test surface consisted of a 2-m2 sheet of stainless steel plate (6 mm thick) onto which 48 X 25 Cm2
numbered quadrants had been etched. This etched matrix established the sampling template for recovery of
Contamination of the test surface was achieved by the application of an organic matrix containing suitable
numbers microorganisms or spores. The organic matrix was manufactured with ¼ strength Ringers or
Thigycollate solution (in the case of Clostridia) containing 3 % Albumin (Cohn fraction) and 2 % Lecithin.
After addition of challenge culture the matrix was mixed and applied by roller to the test surface after
which the system was allowed to dry for 24 hours at ambient temperature. In this manner a dry film of
microbiologically contaminated debris was obtained on the test surface. All challenge organisms were
applied in monoculture or as groups of types within the same genus.
At the end of a cyclic cleaning cycle sequentially involving all test organisms 150 ml of the process liquor
was recovered from the waste chamber. After creating a 1/10 dilution (in Universal quenching agent) and
creating appropriate dilution series, the analysis of residual contamination was determined as described
3.0 Recovery of organisms

Attempts to recover organisms from the test surface were conducted prior to and after treatments involving
steam cleaning.
For each sampling effort 6 X 25 cm2 quadrants were designated by random number. Each designated area
was swabbed with a transport swab pre-moistened in either ¼ strength ringers or Thioglycollate medium
(Clostridial recovery).
Charged swabs were vortexed (1 minute) in either ¼ strength ringers or Thioglycollate medium prior to the
creation of a decimal dilution series. The recovery effort proceeded by spiral plating (50 ul log) of the each
member of the dilution series on an appropriate agar for the challenge organism. Additionally recovery
from the 1 /10 test dilution of treated surfaces was achieved employing membrane filtration followed by
whole membrane incubation on the appropriate agar and a non selective medium. Standard incubation
conditions applied. Confirmation of isolates was achieved by biochemical typing, serology and where
appropriate by genomic analysis.
In the case of the debris reservoir liquor, after creating a 1/10 dilution (in Universal quenching agent) and
creating appropriate dilution series, the analysis of residual contamination was determined as described
4.0 Measurement of operational characteristics

Temperature measurements were conducted on both the test surface and in the steam delivery environment
of the cleaning head.
In the case of surface measurements thermistors were arranged through holes cut in a section of test surface
1 meter long and 0.75 meter wide. These were arranged perpendicular to the line of motion to of the
cleaning head at 50 cm intervals Thermal measurements were taking during reciprocating motion of the
cleaning head over the test surface for a period of 1 minute.
In the case of the cleaning head, a thermistor was located at the geometric centre of the device and a further
two thermistors were located at points where steam vented from the delivery tube.
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Data was recovered by data logger at a sampling rate of 3 measurements per second.
In this manner we able to measure the exit temperature of steam from the delivery tube and that of the
internal environment of the cleaning head.
Measurement of the thermal dynamics of steam treated surfaces was conducted as a separate trial from the
challenge work and the performance with and without vacuum on is reported.
5.0 Form of Use of the “Sage Steam” Cleaning device
In all trials the machine under evaluation was charged with tap water. The device was powered up and
allowed to stabilize until the steam ready indicator actuated. All trials surface challenge trials were
commenced with an empty, sanitized debris bucket charged with either 100mls of 10 % solution of Aqualin
ECO F or dry but containing 4 X 20 gram Sodium dichloroisocyanurate tablets.
Trials were conducted on challenged surfaces both with vacuum in operation.
For any one test organism, a total of four contaminated surfaces were examined. Each surface was cleansed
with the steam device according to the manufacturers’ instructions and each replicate was performed by the
same operator. In practice the surface was treated until it was visually clean which on average accounted 60
seconds treatment under these conditions.
6.0 Test organisms
All organisms employed in this work were obtained as clinical or industrial isolates. During the trial
working cultures were maintained on non selective agar slopes under appropriate conditions of storage.
Spore stocks of the Clostridium difficle strains were generated by recovery of the sediment from
exponential liquid cultures which had been shocked with 96 % Ethanol for 50 minutes.
Microbial suspensions intended for challenge work were prepared by recovery of cell mass from mid
exponential liquid cultures after centrifugation. Cells pellets were washed and re-suspended in Ringers
solution prior to adjustment to the desired cell density by Nephalometry.
Primary recovery medium
Clostridium difficle ( Mixed vegetative/spore A B Clostridium difficle ( Spore Form 3 strains A B 02) -
Acinetobacter lwoffii -
Mycobacterium gordonae -
Aspergillus niger -
S.aureus (MRSA 3 strains) -
Ecoli verotoxic 0157:H7 -
Group A Streptococci ( mixed species) -
Bacillus cereus -
Listeria monocytogenes -
Salmonella seftenberg -
Candida albicans -
Pseudomoas aeruginosa -
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7.0 Environmental monitoring
During the treatment of contaminated surfaces air monitoring was conducted on agar surfaces employing
an impaction device at a sample rate of 100 liters/atmosphere per minute. Additionally open agar plates
were radiated around the axes treatment area commencing at 0.1 meters from the periphery of the treatment
area and then at intervals 0.25, 0.5, 0.75 and 1 meter. These tests were performed to detect any
environmental cross contamination due to steam-generated aerosols during steam/vacuum operation.

8.0 Results

Table 1
Mean thermal performance in the deliver head data of the “Sage Steam” device during standard use.
Mean Steam Vent 1˚C
Mean steam vent 2 ˚C
Centre ˚C

Table 2
Mean thermal performance of a stainless track during standard use of the “Sage Steam” device during
standard use with and without vacuum on.
Vacuum OFF
Treated area 5 seconds after head had passed Single point time above 80˚C during 1 minute treatment of the test piece Single point time above 72˚C during 1 minute treatment of the test piece Vacuum ON
Treated area 5 seconds after head had passed Single point time above 80˚C during 1 minute treatment of the test piece Single point time above 72˚C during 1 minute treatment of the test piece
Table 3
Performance of the “Sage Steam” in the decontamination of challenged stainless steel surfaces by the
application of steam and vacuum processing
Mean Challenge
Mean Survivor
Level cm³
Lever cm³
Removal Removal
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Table 4
Microbiological status of the contents of the debris reservoir after 13 sequential cleaning cycles of the test
environment involving each test culture
No biocide Mean
Dosed Mean
Recovery CFU/ml
Mean Recovery

Table 5
Microbiological status of the peritreatment environment during treatments with the “Sage Steam” device.
CFU/plate CFU/plate CFU/plate CFU/plate
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9.0 Discussion
In this trial we have examined two steam cleaning devices, manufactured by Sage Sanitizing Systems Ltd
under laboratory conditions. These trials were conducted in “dirty” conditions where the challenge
organisms were present in high numbers and the matrix was presented as a dry film on a stainless steel
The goals of the trial included assessment of environmental reduction of the microbiological challenge
together with an understanding of the thermodynamics involved. Additionally we sought to gain some
understanding of the impact of operating the each device upon the environment peripheral to the cleaning
Cleaning systems based on steam generation appear to work by the creation of constantly replaced
pressurized cloud of hot saturated water vapor under a cleaning head. As a general model the impingement
of this vapor and direct steam impact on to surfaces together with the physical action of the head brushes
serve to solubilise organic and microbiological materials.
With earlier generations of steam cleaning devices it was anticipated that the model proposed above would
provide a regime capable of satisfactory levels of antimicrobial sanitization. However, common criticisms
of devices not offering the vacuum option involved the possible generation of microbiologically
contaminated aerosols and sub lethal thermal dosing of organism. Our data suggests that under the
conditions of trial no measurable, pressure generated cross contamination of surfaces outside the treatment
area occurred (Table 5). We did record low levels of atmospheric recovery of Aspergillus niger however
this organism is know to be present in the normal atmosphere of the test environment.
We believe there is strong evidence to suggest that the introduction of the vacuum feature in the
“Sage Steam” devices strategically overcomes the limitations of similar surface sanitizing devices
which rely solely on steam doses.

Our results indicated the range of operational vent temperatures achieved, by the “Sage Steam” devices
studied, range between 99.3˚C and 99.7˚C. These latter data correspond to the generation of core vapor
temperatures ranging from 96.2˚C to 98.2˚C. Although we were unable to measure dwell time of
microbiological debris in the vapor cloud nor assess any protective effect due to lecithin present, it is not
unreasonable, assuming a dwell time of 0.1 seconds or greater, to postulate that any vegetative cells (other
than those of extreme thermoduric organisms or some bacterial spores) present within the cloud would be
inactivated with a high degree of efficiency.
During the generation of the steam and vacuum effect we have recorded treatment surface temperature
maxima of circa 80˚c under standard conditions of use with the temperature minimally falling to circa
62˚C within 5 seconds after the dosage head had passed any single measurement point. Overall we assessed
the time of dosing any of single surface treatment point at a temperature above 72˚C to be minimally circa
11 seconds and circa 6 seconds for temperatures at or above 80˚c. Again conditions likely afford
pasteurization of non thermoduric vegetative cells and bacterial spores.
Considering the observed thermal performance data, we postulated that surface treatment trials would be
successful in the removal of all vegetative microbial forms (and fungal spores) employed as challenge
organisms during these trials. Our data (tables 3 & 4) confirms this prediction where in a greater than
99.999 % removal of all vegetative cells was repeatedly recorded at the treatment surface. However it is
commonly accepted that the spores of Clostridium difficle under optimum conditions of treatment require
exposure to conditions of 80’C for a period 10 minutes to achieve satisfactory levels of log reduction.
Information and statistics reproduced with permission of copyright holder Page - 8 - of 8 SDV8000 Laboratory trials 2009 Our data suggests that > 99.999% spore removal was achieved by the device even though the “Sage Steam”
device under standard conditions of use would not deliver a thermal treatment equivalent to 80˚c for 10
With respect to the performance observed. In the environmental removal of Clostridium difficle spores we
suggest that, not withholding any degree of thermal lethality, the contribution of the nebulisation of spores
by the effects of steam vapor, coupled with that of vacuum removal into a sanitizing solution, is a
distinguishing key operational characteristic of the “Sage Steam” device evaluated during this trial.
These observations are corroborated by the work conducted on the microbiological status of the debris bath
(Table 5) where in our data clearly shows survival and the development of populations of some challenge
organisms ( including Clostridium difficle) ) in the debris reservoir in the absence of an effective biocide.
Relatedly our data suggests that both antimicrobial agents studied were capable of satisfactorily
maintaining an acceptable level of sanitation in the debris reservoir.
10.0 Conclusions
Within the conditions and constraints of this laboratory trial the “Sage Steam” has met the criteria
assigned for successful performance.
In these trials both devices consistently achieved a visually clean post treatment surface with > 99.999
% removal of all challenge organisms under dirty conditions. All test data indicated that the
antimicrobial treatments applied to the debris reservoir achieved satisfactory performance
These objectives were achieved with no measurable level of microbiological contamination of
peritreatment surfaces or the immediate atmosphere.
The data obtained robustly supports the premise that steam cleaning combined with vacuum
removal is an effective technology.
On the basis of the results reported we are pleased to recommend both devices as candidates for flat
surface cleaning solutions in both the medical and industrial environment.
It anticipated that equivalent levels of performance will be obtained in imminent Clinical and
Industrial trials which will afford the opportunity for cross laboratory verification and further
understanding of this cleaning strategy.

D.O’Connor B.Sc. Ci.Biol M.I.F.S.T.

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