Medical Microbiology

156 3 GeneralBacteriology

— LipoidAisresponsibleforthetoxiceffect.Asafreesubstance,orboundup

intheLPScomplex,itstimulates—bybindingtogetherwiththeLPSbinding

protein(LBP)totheCD1 4 receptorofmacrophages—theformationand

secretionofcytokinesthatdetermineclinicalendotoxinsymptomatology.

Interleukin 1 (IL-1)andtumornecrosisfactor(TNF)induceanincreased

synthesisofprostaglandinE2inthehypothalamus,thussettingthe“ther-

mostat”inthetemperaturecontrolcenterhigher,resultinginfever.Other

directandindirectendotoxineffectsincludegranulopoiesisstimulation,

aggregationanddegenerationofthrombocytes,intravasalcoagulationdue

tofactorVIIactivation,adropinbloodpressure,andcachexia.LPScanalso

activatethealternativecomplementpathway.Releaseoflargeamountsof

endotoxincanleadtoseptic(endotoxic)shock.Endotoxinisnotinactivated

byvaporsterilization.Therefore,theparentmaterialsusedinproductionof

parenteralpharmaceuticalsmustbefreeofendotoxins(pyrogens).

— TheO-specificpolysaccharidechainistheso-calledOantigen,thefine

chemicalstructureofwhichresultsinalargenumberofantigenicvariants

usefulinbacterialtyping(e.g.,detaileddifferentiationofsalmonella

types)(seep.284f.).

L-forms(L=ListerInstitute).TheL-formsarebacteriawithmureindefects,

e.g.,resultingfromtheeffectsofbetalactamantibiotics.L-formsarehighly

TheLipopolysaccharideComplex

Lipid Core polysaccharide O-specific

polysaccharide chain

Lipoid A

• Diglucosamine


• Fatty acids

Phosphate

Inner

core region

Outer

core region

Repeating units

consisting of

3–8 sugars

Fatty acids

Diglucosamine

Different

sugars

(heptoses)

Kdo (2-keto-

3-deoxy-octulosonic acid)

Different

sugars

(heptoses)

Fig.3. 12 Thethree-partlipopolysaccharidecomplex(LPS)ofGram-negative

bacteriaisanchoredintheoutermembranebymeansofitslipidmoiety.LPS

isalsoknownasendotoxin.

3

Kayser, Medical Microbiology © 2005 Thieme