Chlorine Dioxide Gas Inactivation of Beta-Lactams
ClorDiSys Solutions, Inc., Lebanon, New Jersey
If a reasonable possibility exists that a non-
penicillin drug product has been exposed to
Allergic reactions to beta-lactams, such as penicil-
cross-contamination with penicillin, the non-
lin, can be life-threatening. Due to the large number of
penicillin drug product shall be tested for the
individuals allergic to beta-lactams, a method for their
presence of penicillin. Such drug product shall
inactivation was explored such that a contaminated
not be marketed if detectable levels are found
area could be treated and re-used. The goal was to
when tested according to procedures specified
validate a cycle that could be used to treat a pharma-
in Procedures for Detecting and Measuring Pen-ceutical manufacturer’s beta-lactam manufacturing equipment for the future production of non-beta-lactam
The U.S. Food and Drug Administration requires
compounds. Testing was conducted using chlorine di-
detection of penicillin G and ampicillin residues in non-
oxide gas at various concentrations and exposure times
beta-lactam pharmaceuticals at the level of 0.03 ppm
in an effort to achieve the pharmaceutical manufactur-
(U.S. FDA, 1999). To ensure the prevention of cross-
er’s required 3-log (99.9%) reduction of eight different
contamination, beta-lactam manufacturing facilities are
beta-lactams on various surfaces. After a period of cy-
often dedicated to the production of beta-lactam prod-
cle development, multiple chlorine dioxide gas cycles at
ucts for the facility’s life and then demolished upon the
various concentrations and exposure lengths were shown effective in inactivating the eight beta-lactam
A method for the inactivation of beta-lactams would
compounds to a successful degree.
allow for equipment and facilities used in the manufac-
ture of beta-lactam products to be used in the future
production of non-beta-lactam products (Kasai et al., 2002). This would allow companies to “recycle” beta-
lactam production facilities instead of demolishing them
Beta-lactam antibiotics are by definition a class of
upon the completion of production. With a novel method
antibiotics which contain a beta-lactam ring in their
of beta-lactam inactivation available, production facili-
structure. They work by inhibiting the formation of bacte-
ties could be more flexible in their functionality and be
rial cell walls by blocking peptidoglycan synthesis (Pratt,
used to produce both beta-lactam and non-beta-lactam
1983). Beta-lactam antibiotics are split into various
products. Increased flexibility for production facilities
groups depending upon their base structure, with the
would lessen the required amount of capital equipment
main groups being penicillins, carbapenems, cephalo-
and the overall footprint necessary, providing substantial
sporins, and monobactams. These antibiotics are used
to treat a variety of gram-positive and gram-negative
With these aims in mind, a study was put forth
bacteria but can also cause adverse effects on patients
to test the efficacy of chlorine dioxide gas (CD) for the
and those who come in contact with them. Allergic reac-
inactivation of beta-lactams. The study was issued by a
tions to beta-lactams are the most common cause of
pharmaceutical company that wished to reuse equip-
adverse drug reactions mediated by specific immunolog-
ment from a decommissioned beta-lactam production
ical mechanisms (Torres et al., 2003). According to the
facility in a different, non-beta-lactam production facility.
CDC, 3%-10% of all adults in the United States have ex-
While previous studies focused on the efficacy of liquid
perienced an allergic response to penicillin (CDC, 2006).
agents (Fukutsu et al., 2006; Takahashi et al., 2008),
Reactions to these allergies can range from simple rash-
this study is the first to focus on a gaseous method. A
es to life-threatening anaphylaxis (Romano et al., 2002).
gaseous method was considered superior as it would
Another possible reaction is blood pressure dropping to
offer the best opportunity to contact all surfaces (interior
life-threatening levels, causing lightheadedness and loss
and exterior) of the contaminated equipment. Chlorine
dioxide gas was the agent selected for testing. CD has
Due to the prevalence and potential severity of beta-
been gaining popularity as a sterilant and decontaminat-
lactam allergies, pharmaceutical manufacturers must
ing agent since the mid-to-late 1980s (Rosenblatt et al.,
take precautions to avoid cross-contamination. The grav-
1985; Rosenblatt et al., 1987). CD in both gaseous
ity of beta-lactam cross-contamination is codified by the
and aqueous phases is a strong oxidizing agent and
U.S. Federal government in Federal Regulation 21 CFR
has about 2.5 times the oxidation capacity of chlorine
(Benarde et al., 1967). Additionally, CD has been ap-
www.absa.org Applied Biosafety Vol. 16, No. 1, 2011
proved for use as a sterilant/decontaminant by the
bapenum group, was the final component inside the
United States Environmental Protection Agency (U.S.
cocktail. Each CI contained 5 μg/mL (§ 5 ppm) inoculat-
EPA, 2005). Both gaseous and aqueous phase CD have
ed on the surface of the CI. The inoculums were dried on
been shown to be effective sanitizing agents that have
the carriers prior to treatment with chlorine dioxide gas.
broad and high-biocidal effectiveness against bacteria
(Benarde et al., 1965; Harakeh et al., 1985; Ridenour et
al., 1949) including pathogens (Harakeh et al., 1985;
CIs were placed inside a 17 ft3 two-glove isolator
Korich et al., 1990; Roberts & Raymond, 1994), viruses
(Biospherix, Ltd., Lancona, NY) complete with CD injec-
(Chen & Vaughn, 1990; Noss & Oliver, 1985), bacterial
tion, sampling, and aeration ports prior to the inactiva-
spores (Ridenour et al., 1949), algae (White, 1972), and
tion cycle. The CD inactivation cycle performed was a
various chemicals and compounds (Bakhmutova-Albert
five-step process. The process begins with a precondi-
et al., 2008; Rodriguez et al., 2007; Ryan et al., 2007).
tioning step. In this step, humidity is raised from ambient
CD has a chlorine-like odor which is detectable at its
conditions to between 60%-75% relative humidity (RH)
8-hour safety threshold (OSHA, 2011). It has a yellow-
because CD has been shown effective as a decontami-
green color, which enables it to be monitored by an ultra-
nating agent within this humidity range (Czarneski,
violet (UV)-VIS spectrophotometer, allowing for tight
2009; Eylath et al., 2003). For these tests, a level of
process control. CD was selected to decontaminate the
75% RH was used. This was followed by the conditioning
Brentwood postal sorting facility and the majority of the
step, where the environment was held at the prescribed
Hart Senate office building, both in Washington, DC,
RH level for a set amount of time. The condition time for
after the anthrax contaminations in 2001 and has also
these studies was 30 minutes. Upon completion of the
been used to decontaminate hospitals, surgical suites,
conditioning step, CD was introduced into the isolator in
laboratories, animal breeding facilities, processing
the charge step. Once the isolator was charged with the
tanks, isolators, and biological safety cabinets (BSCs)
specified concentration of CD, the gas was held at that
level for a prescribed amount of time in the exposure
step. Both the concentration and exposure time were
to be altered during the study to determine the optimal
inactivation cycle. After the exposure step, the isolator
was aerated of CD during the aeration step. Upon
Testing was done using chemical indicators (CI) of
completion of the exposure of the CIs to CD, the CIs were
various materials impregnated with eight types of beta-
sent to a laboratory for evaluation. Control CIs not
lactams, supplied by LCMS Limited (Raleigh, NC). Three
exposed to CD were also sent to provide baseline
carrier materials were selected for testing based on
recovery data to analyze the effect of CD exposure.
their prevalence in the manufacturing and laboratory
A Minidox-M Chlorine Dioxide Gas Generator
workplace. Carrier materials evaluated in this study
(ClorDiSys Solutions, Inc., Lebanon, NJ) was used to con-
were polycarbonate plastic (lexan), stainless steel (304
trol the decontamination cycle. It automated the process
L, passivated), and aluminum (non-anodized). The carri-
by controlling the humidity and chlorine dioxide gas
ers were approximately 15-mm long by 5-mm wide by 2-
concentration throughout the entire cycle. During the
mm thick. A single square-profiled channel approximate-
charge and exposure steps, gas concentrations were
ly 0.5ޤ1.0-mm deep and wide was machined lengthwise
continuously monitored using a validated UV-VIS spectro-
along the center on one side of each coupon to simu-
photometer within the Minidox-M to ensure that the cor-
late the presence of beta-lactam residues in cracks and
rect concentration was reached and maintained (Shah
et al., 2005). This process control allows for repeatability
Each CI was spiked with a cocktail of eight beta-
among the various inactivation cycles. With the ability to
lactams. These eight beta-lactams were chosen to
accurately reproduce the correct cycle parameters, the
represent a sampling of those on the equipment driving
pharmaceutical manufacturer agreed to expose three
this study as well as some other common beta-lactams.
CIs of each carrier material to one inactivation cycle for
For example, amoxicillin was selected as it is reported
validation rather than expose CIs to three separate inac-
to be the most commonly used beta-lactam in the
United States and many other countries (Cars et al.,
Various decontamination cycles of differing concen-
2001; McCaig & Hughes, 1995). The cocktail consisted
trations and exposure times were tested for efficacy
of beta-lactams from the penicillin, cephalosporin, and
towards inactivation of beta-lactams. Table 1 shows the
carbapenum groups. Penicillin G, penicillin V, ampicillin,
various parameters that were associated with each inac-
and amoxicillin were included from the penicillin group.
tivation cycle. Concentrations are measured in milli-
From the cephalosporin group, cefadroxil, cefazolin, and
grams of chlorine dioxide gas per liter of volume (mg/L)
cephalexin were incorporated. Imipenem, from the car-
www.absa.org Applied Biosafety Vol. 16, No. 1, 2011
is 0.1% recovery in relation to control CIs. With approxi-
Upon completion of the inactivation cycles, exposed
mately 5 ppm of each beta-lactam inoculated on each
CIs as well as a set of positive control CIs were shipped
CI, acceptance criteria of 0.1% recovery would equal
to LCMS Limited for extraction and evaluation. In addi-
0.005 ppm or less for each beta-lactam, assuming no
tion, a negative control was processed as well. Liquid
loss on the control CIs. If controls returned with only 4
chromatography (LC) and mass spectrometry (MS) were
ppm recovered, cycle success would be measured at
used during recovery to test for the presence of the beta-
lactams (Straub & Voyksner, 1993; Voyksner et al.,
Results from the recovery testing are presented in
1991) on the CIs. Post-exposure beta-lactam recovery
Figures 1-9. Plotted in each figure are the percentages
was calculated as a percentage of the recovered amount
of each beta-lactam recovered after the inactivation cy-
on exposed CI divided by the recovered amount on the
cles. The 3-log reduction line (0.1% recovered) is shown
control (unexposed) CI of the same type (Table 2).
for reference as a dotted line. A successful inactivation
cycle would have all recovery values below this line.
The three chemical indicators on aluminum carriers
are represented by A-1, A-2, and A-3. Chemical indica-
The pharmaceutical manufacturer’s requirement of
tors on lexan carriers are represented by L-1, L-2, L-3.
achieving 3-log (99.9%) reduction (maximum post-
Chemical indicators on stainless steel carriers are repre-
exposure recovery of 0.1%) was the baseline for ac-
ceptance. By calculating post-exposure recovery as a
To further analyze the data, calculating the total
percentage of exposed/control CIs, loss due to shipping
exposure value by means of the cumulative parts per
and handling becomes irrelevant as acceptance criteria
million-hours for each cycle gives an added depth to
Limits of Quantitation (LOQs) and Limits of Detection (LODs) for the 8 target beta-lactam analytes.
www.absa.org Applied Biosafety Vol. 16, No. 1, 2011
Results from Inactivation Cycle 1 (1 mg/L at a 6-hour exposure).
d Cephalexin % Recovery
Results from Inactivation Cycle 2 (3 mg/L at a 6-hour exposure).
d Cephalexin % Recovery
www.absa.org Applied Biosafety Vol. 16, No. 1, 2011
Results from Inactivation Cycle 3 (5 mg/L at a 4-hour exposure).
d Cephalexin % Recovery
Results from Inactivation Cycle 4 (5 mg/L at a 6-hour exposure).
d Cephalexin % Recovery
www.absa.org Applied Biosafety Vol. 16, No. 1, 2011
Results from Inactivation Cycle 5 (7 mg/L at a 2-hour exposure).
d Cephalexin % Recovery
Results from Inactivation Cycle 6 (7 mg/L at a 4-hour exposure).
d Cephalexin % Recovery
www.absa.org Applied Biosafety Vol. 16, No. 1, 2011
Results from Inactivation Cycle 7 (7.5 mg/L at a 4-hour exposure).
d Cephalexin % Recovery
Results from Inactivation Cycle 8 (9 mg/L at a 2-hour exposure).
d Cephalexin % Recovery
www.absa.org Applied Biosafety Vol. 16, No. 1, 2011
these results. For gaseous chlorine dioxide, 1 mg/L is
equal to 362 parts chlorine dioxide gas per million parts
(ppm) of air. A ppm-hour is a measure of exposure, with
Test results demonstrated that chlorine dioxide gas
1 ppm-hour representing the exposure of 1 ppm of chlo-
was effective towards the inactivation of the eight beta-
rine dioxide gas for the duration of 1 hour. Determining
lactams involved at varying concentrations and exposure
the cumulative exposure using ppm-hours for chlorine
lengths. Nine inactivation cycles were tested, with five
dioxide gas for each cycle consists of multiplying the gas
passing the acceptance criteria of achieving a 3-log
concentration (in mg/L) by 362 (ppm per mg/L) and
reduction of the eight beta-lactams to beneath U.S. Food
then multiplying that number by the exposure time (in
and Drug Administration (FDA)-required 0.03 ppm resi-
hours). Table 3 shows the cumulative exposure in ppm-
due detection level. Inactivation cycles numbered 3, 4, 6,
hours for each inactivation cycle. The successful inacti-
7, and 9 each achieved the targeted 3-log reduction of
beta-lactams on aluminum, lexan, and stainless steel CIs.
Results from Inactivation Cycle 9 (30 mg/L at a 4-hour exposure).
d Cephalexin % Recovery
Cumulative ppm-hours per inactivation cycle.
www.absa.org Applied Biosafety Vol. 16, No. 1, 2011
Successful inactivation cycles which achieved 3-log
reduction of all eight beta-lactam compounds all had
cumulative exposures of over 7,240 ppm-hours. Based
Bakhmutova-Albert, E. V., Margerum, D. W., Auer, J. G., &
on this, it can be concluded that in order to achieve a
Applegate, B. M. (2008). Chlorine dioxide oxidation of dihy-
3-log reduction of beta-lactams, an inactivation cycle
dronicotinamide adenine dinucleotide (NADH). Inorganic Chemistry, 47(6), 2205-2211.
consisting of a 30-minute conditioning phase at 75%
Barza, M. (1985). Imipenem: First of a new class of beta-lactam
relative humidity, followed by an exposure to CD of at
antibiotics. Annals of Internal Medicine, 103(4), 552-560.
Benarde, M. A., Israel, B. M., Oliveri, V. P., & Granstrom, M. L.
Results demonstrate that beta-lactam contaminated
(1965). Efficacy of chlorine dioxide as a bactericide. Applied
equipment and facilities can be treated with CD using a
validated cycle and reused to manufacture non-penicillin
Benarde, M. A., Israel, B. M., Oliveri, V. P., & Granstrom, M. L.
products based on the manufacturer’s risk assessment.
(1967). Efficiency of chlorine dioxide as a bactericide, Jour-
This provides pharmaceutical manufacturers the option
nal of Applied Microbiology, 13, 776.
of reusing capital equipment previously used for beta-
Cars, O., Molstad, S., & Melander, A. (2001). Variation in antibi-
otic use in the European Union. Lancet, 357(9271), 1851-
lactam production. It also provides a means to routinely
treat equipment in an effort to minimize the risk of cross-
Centers for Disease Control and Prevention (CDC). (2006).
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Available at: www.cdc.gov/std/treatment/2006/penicillin-
Chen, Y., & Vaughn, J. M. (1990). Inactivation of human
and simian rotaviruses by chlorine dioxide. Applied
Since the original test study, multiple beta-lactam
Environmental Microbiology, 56, 1363-1366.
facilities have been treated with CD inactivation cycle #3,
Code of Federal Regulations. (2010). Penicillin contamination,
consisting of 30 minutes of conditioning at 75% relative
humidity followed by approximately 7,240 ppm-hours of
Czarneski, M. A. (2009). Microbial decontamination of a 65-
CD exposure. In some cases, the beta-lactam manufac-
room new pharmaceutical research facility. Applied Biosafety:
turing facilities were converted into non beta-lactam
Journal of the American Biological Safety Association, 14(2),
manufacturing facilities post-treatment. In others, the
beta-lactam manufacturing facilities were repurposed as
Eylath, A. S., Madhogarhia, E., Rivera, E., Lorcheim, P., &
Czarneski, M. (2003). Successful sterilization using chlorine
training facilities. These inactivation cycles have all
dioxide gas: Part one-sanitizing as aseptic fillisolator. BioPro-
included the facility’s HVAC systems and all equipment
located inside the facility, including BSCs and production
Fukutsu, N., Kawasaki. T., Saito, K., & Nakazawa. H. (2006). An
and packaging equipment. To test the efficacy of the CD
approach for decontamination of beta-lactam antibiotic
inactivation cycles, the facilities performed swab tests
residues or contaminants in the pharmaceutical
pre- and post-exposure. Swab locations included inside
manufacturing environment. Chemical and Pharmaceutical Bulletin, 54(9), 1340-1343.
HVAC ductwork and inside and underneath equipment,
Harakeh, M. S., Berg, J. C., & Matin, A. (1985). Susceptibility of
among others. Swab tests utilizing liquid chromatography
chemostat-grown Yersinia enterocolitica and Klebsiella
confirmed the effectiveness of the CD inactivation cycles
pneumoniae to chlorine dioxide. Applied Environmental Mi-
in all facilities with zero positive swabs at post-exposure
test locations. These decontaminations proved that the
Kasai, T., Okubo, T., Yamanaka, A., Takahira, M., Takeuchi, M.,
chlorine dioxide gas inactivation cycles could be success-
& Nakamura, K. (2002). ICH Q7A; 4.40 containment of beta-
fully used outside of the controlled laboratory setting.
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ClorDySis’ research on this project was funded by
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the pharmaceutical industry. The author would like to
McCaig, L., & Hughes, J. M. (1995). Trends in antimicrobial
drug prescribing among office-based physicians in the
thank Dr. Robert Voyksner of LCMS Limited for his help
United States. Journal of the American Medical Association,
and support during the study and Dr. Henry Luftman of
DRS Laboratories for his support in writing this article.
National Sanitation Foundation, (2007). Annex G—
Kevin Lorcheim is employed by ClorDiSys Solutions, Inc.
Recommended microbiological deecontamination proce-
Correspondence should be addressed to Kevin Lorcheim
dure,National Sanitation Foundation: Standard No. 49 for Class II (Laminar Flow) Biosafety Cabinetry, G1-G3. Ann Arbor, MI: NSF International.
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Training Announcements Principles & Practices of Biosafety (PPB)
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