Introduction of Bacterial Endotoxin Detection by Chromogenic Method
Table of Contents
Bacterial Endotoxin Detection by Chromogenic Method uses for screening and diagnosis of Gram-negative bacterial infection with a low limit of detection is 1 pg/ml (0.005EU/ml). It also applies to the quantitative detection of endotoxin in pharmaceutical and biological end-products. The low limit of detection is 0.001EU/ml. Endotoxin is heat stable lipopolysaccharide (LPS)-protein complexes that form structural components in Gram-Negative Bacterial cell walls and it is liberated only on cell lysis or death of bacteria.
Principle of Chromogenic Method
In brief, a key principle of the chromogenic method is to reveal the presence of the analyte in a test specimen through chemically-induced visible color changes. The resulting color is then recorded by applying spectrophotometric methods to reveal the concentration of the analyte in the test sample.
Product Characteristics
| Method | Chromogenic | Chromogenic |
| Sample | serum | Dialysate, dialysis water |
| Detection object | Gram-Negative Bacteria | Pyrogen material |
| Detection time | 1 hour | 40 minutes |
| Low detection limit | 1 pg/ml (0.005EU/ml) | 0.001EU/ml |
| Machine to operate on | Goldstream kinetic tube reader | Microplate reader |
Keynotes on Endotoxin
- Endotoxin can be detected other than chromogenic methods are gel-clot and turbidimetric methods.
- A chromogenic method is of two types- Kinetic and end-point chromogenic methods.
Features of Endotoxins
- Endotoxins are lipopolysaccharide of molecular weight 50KDa-1000KDa.
- They are found mostly in Gram-negative bacteria.
- They form an integral part of the cell wall; released only on disruption of the bacterial cells.
- Heat stable
- They are comparatively weakly antigenic. Anatoxins are not formed but antibodies against polysaccharides are raised.
- Toxoids can not be made.
- No enzymic action
- They express low potency.
- They are usually pyrogenic and feverish by induction of interleukin 1 (IL-1) production.
- Lacking specific receptor
- Not filterable
- On boiling they don’t get denatured.
- They are located on chromosomal genes.
- They are detected by Limulus lysate assay.
- Some endotoxins-produced bacteria are Escherichia coli, Salmonella enterica serotype Typhi, Shigella, and Vibrio cholerae.
- Diseases caused by endotoxins-producing bacteria are meningococcemia, and sepsis by Gram-negative rods (GNRs).
Further Reading
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5793131/
- https://textbookofbacteriology.net/endotoxin.html
- https://www.pharmtech.com/view/comparing-endotoxin-detection-methods
- https://www.era-bio.com/article-4675-5877.html
- Jawetz, Melnick and Adelberg’s Medical Microbiology. Editors: Geo. F. Brook, Janet S. Butel & Stephen A. Morse, 21st ed 1998, Publisher Appleton & Lance, Co Stamford Connecticut.
- Mackie and Mc Cartney Practical Medical Microbiology. Editors: J.G. Colle, A.G. Fraser, B.P. Marmion, A. Simmous, 4th ed, Publisher Churchill Living Stone, New York, Melborne, Sans Franscisco 1996.