Introduction to isolators for sterility testing, covering: Sterility testing concerns Introduction to isolators Isolator decontamination cycles Biological indicators Validation of isolator cycles Key operational decisions Maintaining isolators

1. Operation of Sterility Testing
Isolators and validation issues
http://www.pharmamicroresources.com/
https://www.pharmig.org.uk

2. Introduction  Sterility testing concerns
 Introduction to isolators
 Isolator decontamination cycles
 Biological indicators
 Validation of isolator cycles
 Key operational decisions
 Maintaining isolators

3. X
X
 Major concern with the sterility test is the risk of false positives.
 These can lead to expensive and lengthy failure
investigations.
 Proving a false positive is extremely difficult.
 A false positive is a microorganism that has been transferred
through cross-contamination by personnel or from the test
environment.
 This differs to microbial contamination being present in the
product under test.
 Where the sterility test is conducted within a conventional
cleanroom, the risk of cross-contamination is arguably higher than
if the test is conducted within an isolator.

4. Isolators

5. An isolator is an
arrangement of
physical barriers
that are integrated
so that the
workspace (an
enclosed
environment) within
the isolator is
sealed from the
outside
environment.
• Provide a testing environment free from contamination,
through routine sanitization using a validated cycle and
confirmed by environmental monitoring.
• Enable the isolation between the operator and the process.
• May have doors to provide access to the equipment inside the
isolator.
• Have gloveports situated to allow users access to machinery
and product during testing or half-suits.
• Have a mechanism by which materials can be sanitized in place
or moved into the isolator via the use of transfer isolators or
through the use of a rapid gassing port.

6. To maintain the barrier with the
external environment, isolators
consist of either a flexible film
for the outer wall or have a solid
wall envelope.
With the exception of handling
certain medicinal products
isolators used for the sterility
test are at a positive pressure
relative to the room and have a
high efficiency particulate air
(HEPA) filtered airflow.
The maintenance of isolators is important, especially
in ensuring the minimization of leakage.
Isolators are normally tested biannually for HEPA
filter issues.
Regular checks for leakage and pressure differential,
often with alarms in place.

7. • Isolators are most commonly sanitized using hydrogen
peroxide vapor (a surface disinfectant) or peracetic acid.
• Isolators are said to ‘disinfect’, ‘biodecontaminate’ or
to 'sanitize' rather than 'sterilize’.
• Absolute sterility cannot be demonstrated.
• Sanitization, in this context, describes the reduction
of a number of microorganisms within the clean
environment as demonstrated through the use of
biological indicators in validation studies for different
isolator cycles.
Biodecontamination # 1

8. Biodecontamination # 2
• Hydrogen peroxide vapor disinfection employs a free
radical reaction mechanism to facilitate microbicidal
action.
• Hydrogen peroxide always decomposes (or
disproportionates) exothermically into water and
oxygen gas spontaneously.

9. Biodecontamination # 3
VHP
• Reliant on a high vapour phase concentration - achieved by initial dehumidification of the air.
• The process uses 30-35% hydrogen peroxide liquid which is flash evaporated to achieve the
required vapour phase concentration.
• The process is always stopped before the dew point is reached - a “Dry” process.

10. Biodecontamination # 3
HPV
• The process also flash evaporates 30-35% hydrogen peroxide to create a vapour.
• No initial dehumidification.
• The process is brought beyond the dew point to saturated vapour conditions.
• The process relies on the formation of micro-condensation on surfaces - a “Wet” process.
• Reliant upon ambient temperature and humidity.
iHP
• Less common, produced by ultrasonics.

11. QUALIFYING AN ISOLATOR
FOR STERILITY TESTING
A CASE STUDY

12. This presentation examines the important operational criteria for an isolator used for sterility
testing.
Looking at aspects of validation and the maintenance program.
This examination takes the form of a study proposal.
The isolator system consists of two solid wall Type 1 positive pressure isolators linked by a rapid
gassing port.
The gassing port and the isolators are attached to a gas generator.

13. Images of the isolator examined – taken by Tim Sandle

14. Introducing isolator
decontamination cycles

15. ISOLATOR CYCLE: STEP 1
Pre-cycle Disinfection
Prior to final product items (and other material that is not sterilized and contained within double
wrapping) being loaded into the isolator or gassing port, items should be disinfected.
A rationale for the inclusion of this step is that gaseous disinfection requires a pre-cleaning step.
The target of the gaseous disinfection process is surface bio-decontamination and does not match
the performance of defined penetrative sterilization processes detailed in pharmacopeia.
Surface gaseous disinfection requires a starting condition wherein a surface is visibly clean of soiling.
Visible contamination or soiling may occlude microorganisms from the disinfection process.

16. ISOLATOR CYCLE: STEP 2 (A)
Gassing Port and Disinfection Cycles
The gassing port is designed to sanitize the different sterility test
loads in a faster time than would be possible if loads were placed
inside an isolator for sanitization.
The gassing port is connected to a gas generator.
Because hydrogen peroxide in the passive state is very poor at
diffusion, the function of the gas generator is to heat the
hydrogen peroxide to produce a vapor and to provide the
generated vapor to the port.

17. ISOLATOR CYCLE: STEP 2 (b)
Gassing Port and Disinfection Cycles
The function of the port is to actively distribute the vapor via a
distribution nozzle.
The function of the rotating nozzle is to prevent hot spots arising
from an uneven distribution of the gas.
The dosage of the hydrogen peroxide is controlled by the user
prior to placing the chemical into the gas generator.
When loading an isolator or port, the presentation of surfaces to
the sanitization process is extremely important. Material loads
often rely on point contact support, via wire racking or hangers, to
assure exposure to the disinfection agent.

18. ISOLATOR CYCLE: STEP 3 (a)
Sanitization Cycle #1
The sanitization process occurs by an aqueous solution of
hydrogen peroxide being evaporated to produce the same
weight ratio in the vapor phase as in the source liquid.
This vapor is transported to the chamber to be bio-
decontaminated in a heated carrier gas (initially sterile
compressed air).
Vapors are circulated around the chamber, then through a
catalysing filer at the end of sanitization to break down the
hydrogen peroxide.

19. ISOLATOR CYCLE: STEP 3 (b)
Sanitization Cycle #1
The sanitization stage (or what is sometimes called ‘bio-
decontamination’) functions within the chamber by
depositing an even layer of hydrogen peroxide over all
surfaces.
In this case study – a micro-condensation process.
Optimum kill conditions require dew point to be reached,
which is affected by various parameters.

20. ISOLATOR CYCLE: STEP 3 (c)
Sanitization Cycle #2
There are some key steps to ensure an optimal hydrogen peroxide vapor disinfection process:
1. Vaporization of liquid to small molecules–gas phase delivery to target volume.
2. Development of the gas concentration in the target environment to saturated vapor conditions, past
dew point, and transition into liquid phase.
1. With this case study: at saturated vapor conditions, the gas concentration can hold no more
molecules, thus, the process of condensation formation and disinfection agent surface
deposition starts.
3. Re-evaporation of the surface condensate and removal of residual gas to target endpoint
concentration.

21. ISOLATOR CYCLE: STEP 3 (d)
Sanitization Cycle #3
The sanitization cycle operates through the following steps:
1. The generator initially dehumidifies the ambient air (conditioning). Here, initial temperature and
relative humidity is optimized before vapor injection.
2. The generator then produces hydrogen peroxide vapor by passing aqueous hydrogen peroxide over
a vaporizer.
1. The gassing phase is validated to deliver a disinfection agent dose volume that will reach
required in the target area and on target surfaces.
3. The vapor is circulated at a programmed concentration in the air and held for a set period of time
(dwell phase).
4. After the hydrogen peroxide vapor has circulated in the enclosed space for a pre-defined period of
time, it is circulated and broken down into water and oxygen to safe levels, at 1 parts per million
(ppm).

22. ISOLATOR Cycle
Primary process variables for hydrogen peroxide vapor disinfection
include:
Starting relative humidity (RH) Surface and environmental
temperatures
Gas distribution for a homogeneous deposition of vapor and
resulting surface condensate
The amount of evaporated hydrogen peroxide solution dosed into
the target volume (g/min)
Surface area for condensate distribution together with amount of
surface absorbency (e.g., packaging).
It is important that these process variables are controlled

23. Validation of isolator cycles

24. Biological indicators
With this case study, the gassing cycles were validated and developed
using biological indicators.
The indicators used were Geobacillus stearothermophilus spores dried
onto stainless steel discs.
ATCC 7953 or 12980.
The microorganism used as the biological indicator should have a
higher population and resistance than the bioburden on the item to
be decontaminated
Metal discs placed in Tyvek pouches (polyethylene fibre)
The microorganism must geminate under defined conditions in a
standard culture media.

25. Biological indicators
Hydrogen peroxide is a surface disinfectant; therefore, it is important that the biological indicators
are presented to ensure maximum surface area exposure.
Need to determine number and location.
To place in the isolator the envelope must be folded back so that the biological indicator does not
lying flat on a surface.
Kapton tape can be used.
After the exposure of each biological indicator, the discs must be transferred into tryptone soya
broth and incubated at 55-60 C for a minimum of 7 days.
Temperature range suitable for the recovery of thermophilic bacteria.

26. Developing load patterns #1
An important part of the OQ and PQ stages is with the development of load patterns for sterility
testing.
For this: The different sterility test load combinations were mapped out.
These were evaluated for the smallest and largest configurations by assessing the different
load types (this was assessed by calculating the surface area and by an assessment of the
degree of absorbent material).
OQ data demonstrated that the maximum load was the worst-case.
Once assessed, the maximum load was evaluated against biological indicators using
different cycle parameters.
A cycle that achieved total biological indicator kill was chosen as a base cycle and performed
on three occasions.
Routine cycle parameters were then established by incorporating an ‘overkill’ for gassing agent
volume and dwell time to ensure a robust cycle.
During performance qualification each different load type was assessed using biological
indicators and the established routine cycle.

27. Developing load patterns #2
Duplicate biological indicators were used at each location due to the theoretical
risk of ‘rogue’ biological indicators.
The following strategy was applied:
Both duplicates indicate no growth–test pass.
Both duplicates indicate growth–test failure. Here cycle parameters to be
reviewed.
One duplicate indicating growth and one no growth–raise out-of-
specification investigation.
Repeat in triplicate: all replicates must indicate no growth for cycle
acceptance.
Once established, the load patterns became the standardized load patterns for
sterility testing. No significant changes were permissible without undertaking a
new load qualification.

28. When to requalify isolator loads?
An important consideration is the frequency of isolator load requalification and, when undertaken,
the types of load patterns required.
As a minimum this is ordinarily the largest size for each load type.
Requalification is to verify that the isolator system and gassing port continue to operate as
expected; that is to demonstrate that the gassing system continues to kill a known population of
resistant spores (a ‘kill’ or ‘no kill’ test).
In relation to this study proposal, the decision taken was to re-qualify the entire isolator system
using biological indicators on an annual basis.

29. OTHER OPERATIONAL DECISIONS

30. Frequency of decontamination
The frequency of sanitizing the entire isolator system needs to be established.
This was a separate activity to the gassing of each load required for the sterility
test in the gassing port.
In part, this decision was based on environmental monitoring data.
For this study protocol, the two isolators and the gassing port were sanitized
empty once per week.
The purpose of this was to:
Minimize the risk of microorganisms surviving within the isolator chamber.
After a considerable period of satisfactory data, the frequency could be
extended.
Additional supporting data can be provided from conducting post-sanitization
microbial monitoring.

31. Routine cleaning and disinfection
There will be occasions when the inside of the isolator should be
cleaned and disinfected, such as following a spillage incident.
The cleaning and disinfection agents should be carefully selected.
The disinfectant of choice, given that most isolators are
constructed from stainless steel, is 70% IPA or hydrogen peroxide.
This is because many other disinfectants, such as chlorine
based ones, could damage the stainless steel inner chamber
of the isolator (by causing scratching, rouging, and etc.).
Seventy percent IPA may not be appropriate for cleaning
perspex visors; sterile filtered water can then be used to
remove any debris.

32. Frequency of glove changes
Isolator gloves are prone to leakage, and this represents a weak
point with any isolator system.
Some users test all gloves for leakage before and after each test.
One problem here is that leak-testing devices are not available
for all types of isolators, and those that are available can be
unreliable.
Where leak testing is difficult to perform, some users adopt a policy
to change the gloves on a regular basis (such as weekly) with a
visual inspection before and after each test.
Additional supporting data for a glove change policy can be
provided from post-sterility test and post-sanitization microbial
finger plate monitoring.
The use of a water intrusion test for gloves that have been changed
can provide further data as to the frequency that leaks occur.

33. Environmental monitoring
Environmental monitoring should be conducted for each sterility test.
The testing isolator environment should be monitored every time a
sterility test is performed: air-samples (using a volumetric sampler) and
settle plates (during the test); and finger plates, swabs, or contact
plates (immediately post-test).
Action levels are based on EU GMP Grade A environment,.
Static state particulate monitoring is performed regularly.
Environmental monitoring data is used to show the level of
contamination inside the isolator, and, if a final product fails a sterility
test, the data will be used to help determine the validity of the test.
The culture media used should be subjected to inhibition studies.
The room in which the isolator system is housed will also be subject to
viable and particulate monitoring.

34. Isolator housing room
Many isolators are held within a cleanroom or a controlled environment.
The isolator described in this study protocol was held within an EU GMP Grade D/ISO 14644
class 9 (‘in operation’) cleanroom.
Where a cleanroom is used, the cleanroom will have to meet various operational parameters
itself. These parameters will include:
Positive pressure differential to the outside corridor
Controlled temperature and humidity.
High efficiency particulate air (HEPA) (with filters of 99.995% efficiency)
Controlled air-changes
Particles monitored in the dynamic state
Room subject to viable environmental monitoring room falls under a routine maintenance
plan including classification.

35. Maintaining sterility testing
isolators

36. In order for an isolator to function as required, a number of physical attributes
and tests must be performed and measured, such as:
Volume of hydrogen peroxide used
Gas concentration alert level
Alarm status during the cycle
Gas injection phase time
Humidity at the start of gassing.
Selected parameters should also be trended.
Useful reference point is: ISO 14644 Part 7

37. Cycles: temperature and humidity
Case study:
Gas injection temperature:
Alarms set at 41oC to 50oC (determined during OQ)
This temperature range is important in order to determine that the gas entering
the chamber is within the correct range to create a vapor of the required level
of saturation.
Temperature inside port:
15–30oC (operation of the gassing port during the gassing cycle).
This is part of the conditioning phase. The risk of the air temperature being
affected by cold external air upon the isolator is minimal
Humidity:
15-70% RH
The gassing port is designed to condition the air prior to its passing through the
isolator system or from the commencement of gassing.

38. Gassing time
Time is an important parameter.
If the time falls outside the set range, then the gassing cycle will probably be ineffective.
The cycle parameters of peroxide injection rates and phase times were initially developed to
ascertain the required gas concentration profile during the qualification.
Gassing dwell time is set during the cycle development stage of OQ for each different cycle

39. Positive pressure
Positive pressure relative to the isolator room is required to prevent the ingress of
contamination from the outside environment into the enclosed clean zone.
The minimum specification of +20 Pa is the lowest setting to prevent this occurrence and to
leave some safety margin.
The maximum specification of 250 Pa relates to the integrity of the isolator chamber.

40. Leak rate test of the isolator
From a starting pressure of 150 Pa, a timed sequence of monitoring leakage over a 90 second
period is undertaken. By the end of the 90 seconds the pressure must not fall by more than 25 Pa.
From ISO 14644-7

41. Air and airflow
Maintaining the Grade A zone
HEPA filtered H14 standard
Although unidirectional airflow is not required for a sterility testing isolator, there is a theoretical
argument that the airflow should demonstrably remove contamination.
Air speed should be 0.45 meters per second (ms-1) at the filter face (±20%)
A set number of air changes is necessary for the dilution and removal of any potential
contaminants from the isolator environment.
Particle levels:
0.5 µm = 3, 520 counts per cubic meter 5.0 µm = 20 counts per cubic metre

42. This presentation examined a case study for an isolator system used
for sterility testing drawing upon personal experience.
The study focused on the development of cycles with reference made
to validation parameters and to the critical physical parameters that
require monitoring for routine sanitization cycles and maintenance of
the isolator.
Further reading:
Sandle, T. and Tours, N. (2013). Validation and Operation of a
Sterility Testing Isolator: a Study Proposal, Journal of Validation
Technology, Vol. 19, No.1

43. Summary
Sterility testing concerns
Introduction to isolators
Isolator decontamination cycles
Biological indicators
Validation of isolator cycles
Key operational decisions
Maintaining isolators

44. THANK YOU
Dr. Tim Sandle
Pharmaceutical Microbiology:
http://www.pharmamicroresources.com/
Pharmig: https://www.pharmig.org.uk