The document discusses the bacterial endotoxin test, which is used to detect or quantify endotoxins from gram-negative bacteria. It defines endotoxins as lipopolysaccharides found in the outer membrane of gram-negative bacteria that are released upon cell lysis. The test utilizes a gel clot formation reaction that occurs when endotoxins interact with amoebocyte lysate from the horseshoe crab. The document outlines the principle, materials, procedures, controls, and interpretation for the gel clot technique of performing the bacterial endotoxin test on pharmaceutical products to ensure quality standards are met.

1. Bacterial
Endotoxin Test
SHRIVARDHAN DHEEMAN
M.Sc., Microbiology
Gurukul Kangri University,
Haridwar, U.K.
shrivardhandheeman@rediffmail.com
www.sites.google.com/site/shrivardhandheeman
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A presentation on
Bacterial Endotoxin Test
A part of project report on
Analytical Microbiology for Quality
Measurement of Pharmaceutical Product in
Industry
For partial fulfillment of the requirement for the award of
M.Sc., Microbiology
Submitted to
Prof. G.P. Gupta (H.O.D)
Department of Botany and Microbiology
Gurukul Kangri University, Haridwar, U.K. (India)
Under Supervision of
Mr. Roki Pal
Sr. Microbiologist (Executive)
Eurolife Healthcare Pvt. Ltd., Roorkee

3. Bacterial Endotoxin Test
• We will understand:
• What is bacterial endotoxin?
• Which kind of bacteria produces endotoxin?
• What difference between endotoxin and exotoxin?
• How pharmaceutical product contaminate with endotoxin?
• Why it is require to test?
• We will elaborate:
• Principle of bacterial endotoxin test
• Bacterial Endotoxin Test
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4. Bacterial Endotoxin
• The term endotoxin was coined by Richard Friedrich
Johannes Pfeiffer.
• He considered a toxin kept "within" the bacterial cell and to
be released only after destruction of the bacterial cell wall.
• The term endotoxin is used synonymously with the
term lipopolysaccharide.
• The key effects of endotoxins on vertebrates are mediated by
their interaction with specific receptors on immune cells such
as monocytes, macrophages, dendritic cells, and others. Upon
challenge with endotoxin, these cells form a broad spectrum
of immune mediators such as cytokines
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5. Bacteria Produce Endotoxin
• Specially Gram negative bacteria produce endotoxin
(pyrogen).(exceptionally Bacillus thuringeinsis, a gram
positive bacteria produce delta toxin as endotoxin.)
• The example of endotoxin are lipopolysaccharide (LPS) and O
antigen (O specific side chain) found on the outer membrane
of various Gram negative bacteria.
• LPS consists of a polysaccharide (sugar) chain and a
lipid moiety, known as lipid A, which is responsible for the
toxic effects
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6. Endotoxin and Exotoxin
Endotoxin
• Lipopolysaccharide complex on the
outer membrane; lipid A portion is
toxic.
• Cause meningococcemia, fever, death
etc.
• Similar effect of all toxin.
• Heat stable to 250ºC
• Part of outer membrane of gram
negative bacteria.
• Found in only gram negative bacteria;
released on bacterial death and some
liberated during growth.
Exotoxin
• Made of two component (A and B)
• Cause botulism, diptheria, tetanus
etc. disease.
• Highly variable effect on host of
different toxin.
• Heat sensitive and inactivated at 60-
80ºC
• Excreted outside the living cell
• Produced by both gram positive and
gram negative bacteria.
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7. Contamination of pharmaceutical
product with endotoxin
• During water purification for WFI
• During production
• During DNA isolation (Vaccine production)
• During toxoid isolation(Vaccine production)
• By pyrogenated vials (I.V./I.M./pediateric)
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8. Why we test?
• As a essential test for quality control of
pharmaceutical product.
• It will be fatal if drug administrated by human.
• Monitor product contamination during
handling and processing.
• Complies the product standard as GMP, WHO,
HACCP & ISO regulation.
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9. Principle of bacterial endotoxin
test
• The test is based on the observation that when a endotoxin
contacts clot protein from circulating amoebocyte of horse
shoe crab (Limulus) a gel clot forms.
• The preclotting enzyme activated by bacterial endotoxin
(lipopolysaccharide) and calcium to form active clotting
enzyme.
• Active clotting enzyme that catalyzes the cleavage of
procoagulogen into polypeptide subunit (coagulogen).
• The subunit join by disulfide bond to form a gel-clot.
Spectrophotometery is then used to measure the precipitated
by the lysate.
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Endotoxin Sample
Proclotting
enzyme
(Inactive)
Proclotting
enzyme
(Active)
Procoagulogen
Ca++
Coagulogen
(insoluble)Gel-clot

11. Bacterial Endotoxin Test
• The test for bacterial endotoxin is used to detect or quantify
endotoxin of gram negative bacterial origin using amoebocyte
lysate from horseshoe crab (Limulus polyphemus).
• There are three general technique for this test among which
one is most essentially accepted.
– Gel clot technique: based on gel formation.
– Turbidimetric method: based on development of turbidity after
cleavage of an endogenous substrate.
– Chromogenic method: based on the development of color after
cleavage of a synthetic peptide-chromo-gen complex.
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12. Gel-clot Technique
• Apparatus:
– Depyrogenated glassware
– Microtitre tubes
– Micropipette
– Depyrogenated tip
• Equipment:
– Heating block
• Material:
– CSE: Control Standerd Endotoxin
– LAL: Limulus Amoebocyte Lysate
– LRW: LAL Reagent Water
– Product sample: Metronidazole IV
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13. Gel-clot Technique
• Procedure:
• Set up BET Kit
• Switch ON heating block and set on desirable temp.
• Reconstitute CSE Vial
• Dilute CSE Vial in reference to Lysate sensitivity.
• Dilute sample as per MVD.
• Add 50 µl product sample (diluted) in four Microtiter tube, two for
Positive Product Control (PPC) and two for Negative Product Control
(NPC).
• Add 100 µl LRW in two more Microtitre tube (depyrogenated) for
Negative Test Control (NTC).
• Add 50 µl LRW in two more Microtitre tube for Positive Test Contorl
(PTC).
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14. Gel-clot Technique
• Add 50 µl CSE form Sol E (0.125 EU/ ml) in both PPC and PTC and
vortex for 15 min.
• Add 50 µl LRW in NPC and vortex for 15 min.
• Add 100 LAL reagent in each tube.
• Palace each tube in heating block and incubate for 1 hrs. at 37˚C
• Observe after 1 hrs exactly for best interpretation.
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NPC
-R1
NPC
-R2
NTC
-R1
NTC
-R2
CSE LRW
LAL
Product
50 µl CSE
50 µl product sample
100 µl LAL reagent
100 µl LRW
50 µl LRW
50 µl LRW
PPC
-R1
PPC
-R2
PTC
-R1
PTC
-R2

16. Gel-clot Technique
• Observation:
• PPC: Gel clot formed
• PTC: Gel clot formed
• NPC: No gel clot formed
• NTC: No gel clot formed
• Interpritation:
• PPC and PTC control enriched with CSE. So, it formed gel clot.
• Result:
• Product has no detectable endotoxin and complience
USP/IP/BP/IH specification. Endotoxin less then 0.125 EU/ml.
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17. Thank
You
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18. CSE vial Reconstitiution
• Reconstitution of CSE vial:
– The CSE vial reconstitute as caliberated against the IU/EU
per vial.
– Reconstitution as per direction on the vial with LRW.
– Vortex the vial at least 15 min. for well mixing.
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19. Product Dilution
• Preparation of test solution:
– Prepare the sample solution to be test by dissolving or
diluting active substance using LAL reagent water. Dilution
factor determined according Maximum Valid Dilution
(MVD)
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20. CSE Dilution
• CSE dilution: (500 EU/ml) (1 ml = 1000 µl)
100 µl CSE : 900 µl LRW = 50 EU/ml (Sol A)
100 µl Sol A : 900 µl LRW = 5 EU/ ml (Sol B)
100 µl Sol B : 900 µl LRW = 0.5 EU/ml (Sol C)
100 µl Sol C : 100 µl LRW = 0.25 EU/ml (Sol D)
100 µl sol D : 100 µl LRW = 0.125 EU/ml (Sol E)
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21. Maximum Valid Dilution (MVD)
• MVD is the maximum allowable dilution of a sample at which the
endotoxin limit can be determined the MVD using the following formulae.
• Product: Metronidazole IV
• Endotoxin limit: 0.5 EU/ml
• Product Concentration: 0.35 mg/ml
• Lysate sensitivity: 0.125 EU/ml
• Calculation:
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Endotoxin Limit x Product Concentration
MVD = ------------------------------------------------------------------
Lysate sensitivity
5 x 0.35
MVD = --------------
0.125
MVD = 14

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