Destruction of Typical Endotoxins by Dry Heat as Determined Using LAL Assay and Pyrogen Assay

Tohru Nakata

Abstract

The kinetics of destruction by dry heat of two typical endotoxins, Escherichia coli 055:B5 (E. coli endotoxin) and Salmonella abortus equi (S. abortus equi endotoxin), were determined using the Limulus Amebocyte Lysate (LAL) and pyrogen assays. The efficiency of recovery of these endotoxins from carriers using a pyrogen assay was also determined simultaneously. In the LAL assay 0.1–10,000 EU was used and 10–1000 EU in the pyrogen assay. Recoveries of E. coli endotoxin and S. abortus equi endotoxin were, respectively, 49.7–92.0% and 27.0–70.1% by the LAL assay, and 31.1% and 60.6% by the pyrogen assay. Fourier transformation infrared (FT–IR) spectra demonstrated the presence of chemical structural differences between the two endotoxins. By dry heat (200 or 250°C), there were no significant differences in the destruction kinetics between the two endotoxins; either endotoxin can therefore be adapted for use in the endotoxin challenge test. Destruction in the pyrogen assay was significantly quicker than that predicted by the LAL assay for each of the two endotoxins. In this endotoxin destruction system, 3 log cycle reduction (the United State Pharmacopeia (USP) recommendation for the depyrogenation process) could not be obtained by challenge with 10,000 EU of endotoxin under the depyrogenation conditions of 200°C for 60 min (a set of conditions described in the European Pharmacopoeia (EP)), though little pyrogenicity remained. On the other hand, at 250°C for 30 min (a set of conditions described in the EP, USP and Pharmacopoeia of Japan (JP)), a 3 log cycle reduction was achieved without any pyrogenicity remaining.

Received October 5, 1992.
Accepted March 8, 1993.

PDA members receive access to all articles published in the current year and previous volume year. Institutional subscribers received access to all content. Log in below to receive access to this article if you are either of these.

If you are neither or you are a PDA member trying to access an article outside of your membership license, then you must purchase access to this article (below). If you do not have a username or password for JPST, you will be required to create an account prior to purchasing.

Full issue PDFs are for PDA members only.

Note to pda.org users

The PDA and PDA bookstore websites (www.pda.org and www.pda.org/bookstore) are separate websites from the PDA JPST website. When you first join PDA, your initial UserID and Password are sent to HighWirePress to create your PDA JPST account. Subsequent UserrID and Password changes required at the PDA websites will not pass on to PDA JPST and vice versa. If you forget your PDA JPST UserID and/or Password, you can request help to retrieve UserID and reset Password below.