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Role of meningococcal endotoxin in meningococcal purpura
Abstract:
Enteric bacilli and meningococci (MGC) both contain potent endotoxins, but purpuric skin lesions indistinguishable from the experimental dermal Shwartzman reaction are much more common during meningococcal bacteremia than during bacteremia with enteric organisms. Highly purified lipopolysaccharides (LPS), virtually free of contamination by protein, RNA, and capsule, were extracted by a modification of the phenol-water technique from MGC (serogroups A, B, and C) and enteric bacilli (Escherichia coli 04 and 0:111, and Salmonella typhimurium). Polysaccharides in these LPS were similar by gas chromatography except for one galactose-deficient strain of MGC (135B). LPS from MGC and enterics were equally potent for the general Shwartzman reaction and mouse lethality, but LPS from MGC was 5-10 times more potent in inducing the dermal Shwartzman reaction. The greater skin potency of LPS from MGC explains the prominence of purpura in meningococcemia. Comparison of the properties of LPS may explain other differences in clinical syndromes caused by gram-negative bacteria.
Insights
Lipopolysaccharides (LPS) from meningococci (MGC) are more potent in causing skin reactions than those from enteric bacteria. This difference explains why purpura is more common in meningococcal infections.
Area of Science:
- Microbiology
- Immunology
- Toxicology
Background:
- Gram-negative bacteria, including enteric bacilli and meningococci (MGC), produce endotoxins.
- Purpuric skin lesions are a common clinical manifestation of meningococcal bacteremia, but less so with enteric bacteremia.
- The Shwartzman reaction is a model for understanding endotoxin-induced tissue damage.
Purpose of the Study:
- To compare the endotoxin potency of lipopolysaccharides (LPS) from MGC and enteric bacilli.
- To investigate the role of LPS in the pathogenesis of purpuric skin lesions.
- To elucidate differences in clinical syndromes caused by gram-negative bacteria.
Main Methods:
- Extraction of highly purified LPS from MGC (serogroups A, B, C) and enteric bacilli (E. coli, S. typhimurium) using a modified phenol-water technique.
- Gas chromatography analysis of LPS polysaccharide composition.
- Assessment of Shwartzman reaction (general and dermal) and mouse lethality in response to LPS.
Main Results:
- LPS from MGC and enteric bacilli showed similar potency in the general Shwartzman reaction and mouse lethality.
- LPS from MGC was 5-10 times more potent than enteric LPS in inducing the dermal Shwartzman reaction.
- Polysaccharide composition of LPS was generally similar, with one notable galactose-deficient MGC strain.
Conclusions:
- The enhanced potency of MGC LPS in the dermal Shwartzman reaction explains the higher incidence of purpura in meningococcemia.
- Differences in LPS properties can contribute to distinct clinical presentations of infections caused by gram-negative bacteria.