248 4 BacteriaasHumanPathogens&Gasgangrene(clostridialmyonecrosis).Anaggressiveinfectionofthe
musculaturewithmyonecrosisandtoxemia.Theincubationperiodvaries
fromhourstoafewdays.
Diagnosis.Thediagnosticprocedureincludesidentificationofthepathogens
inrelevantmaterialsbymeansofmicroscopyandculturing.Identificationof
anaerobicallygrownculturesisbasedonmorphologicalandphysiological
characteristics.
Therapy.Primarytreatmentissurgical,accompaniedbyantibiosis(penicil-
lins,cephalosporins).TreatmentwithhyperbaricO 2 inspecialcentershas
provedeffective:patientsbreathepureO 2 throughatubeormaskinapres-
surechamber(3atm= 303 kPa)severaltimesduringtwo-hourperiods.
Epidemiologyandprevention.Truegasgangreneisnowararecondition.
Timelyoperationofcontaminatedwoundsisthemainpreventivemeasure.Clostridiumtetani(Tetanus)..........................
Tetanus(lockjaw)isanacuteclostridialdisease,itsclinicalmanifestationsdo
notresultdirectlyfromtheinvasiveinfection,butarerathercausedbya
strongneurotoxin.
Toxin.Tetanospasmin(anABtoxin,p. 1 6)consistsoftwopolypeptidechains
linkedbyadisulfidebridge.Theheavychainbindsspecificallytoneuronre-
ceptors.Thelightchainisazinc-metalloproteasethatisresponsibleforpro-
teolysisofcomponentsoftheneuroexocytosisapparatusinthesynapsesof
theanteriorhornsofthespinalcord.Thisstopstransmissionofinhibitory
efferentimpulsesfromthecerebellumtothemotorendplates.
Pathogenesis andclinicalpicture. These ubiquitouspathogens invade
tissuesfollowinginjuries(Fig.4.8a).Givenanaerobicconditions,theypro-
liferateandproducethetoxin(seeabove),whichreachestheanteriorhorns
ofthespinalcordorbrainstemviaretrogradeaxonaltransport.Theclinical
pictureresultingfromtheeffectsofthetoxinischaracterizedbyincreased
muscletoneandspasmsinducedbyvisualoracousticstimuli.Thecramps
oftenbegininthefacialmusculature(risussardonicus,Fig.4.8b),thenspread
toneckandbackmuscles(opisthotonus).Thepatientremainslucid.
Diagnosis.Thepreferredmethodistoxindetectioninwoundmaterialinan
animaltest(mouse)basedeitheronneutralizationordetectionofthetoxin
genewithPCR.Thepathogenisdifficulttoculture.
Therapy.Antitoxictherapywithimmuneseraisappliedfollowingameti-
culouswoundcleaning.Thepatient’smusculaturemustalsoberelaxed
withcurareorsimilaragents.4
Kayser, Medical Microbiology © 2005 Thieme