The Endotoxin Conundrum
Outsourced Pharma's in-depth look at an issue preoccupying the microbial detection field.
Earlier this year, John Dubczak, the General Manager of Microbial Solutions at Charles River, wrote about how the unresolved issue of low endotoxin recovery remains the hot issue in the testing of these highly toxic, heat stable lipopolysaccharides (LPSs). He has since followed up with a well-documented article in Outsourced Pharma, posted last week that lays out nicely the LER conundrum. LER, the inability to recover a spiked amount of lipopolysaccharide (LPS), was first reported about four years ago at a scientific meeting, and has dominated conference agendas ever since. So why is this of interest?
Endotoxins can trigger severe inflammatory fever reactions in patients, so regulatory authorities require companies to screen vaccines, drugs and medical devices like artificial kidneys that, for various reasons, remain particularly vulnerable to LPS contamination. The favored test for years has been the Limulus Amebocyte Lysate (LAL) test, which contains the blood of the horseshoe crab. Apparently, certain agents, such as surfactants, appear to denature purified LPS to the point where it is no longer detectable using LAL (see Images below), though how much of an issue this really is remains a matter of debate.
Scientists largely agree that LER is not a public health risk, and there have been no reported endotoxin outbreaks due to a failure of the LAL test. But LER does appear to present a problem in validating product hold-times, notes Dubczak in the Outsourced Pharma article. "Many of us have seen endotoxin activity decrease over time, but the problem with the rapid decay of LPS spiked, undiluted biological samples is one that is tied to the analyte itself," he says.
Images. LPS in water, on left, and after the surfactant Tween is added, which can denature purified LPS.
(Photos credit: Charles River Microbial Solutions)