Medical Microbiology

Bacillus 245

Bacillusanthracis(Anthrax)...........................

Occurrence.Anthraxoccursprimarilyinanimals,especiallyherbivores.The

pathogensareingestedwithfeedandcauseasevereclinicalsepsisthatis

oftenlethal.

Morphologyandculturing.Therodsare 1 lmwideand 2 – 4 lmlong,non-

flagellated,withacapsulemadeofaglutamicacidpolypeptide.Thebacte-

riumisreadilygrowninanaerobicmilieu.

Pathogenesisandclinicalpicture.ThepathogenicityofB.anthracisresults

fromitsantiphagocyticcapsuleaswellasfromatoxinthatcausesedemas

andtissuenecrosis.Humaninfectionsarecontractedfromdiseasedanimals

orcontaminatedanimalproducts.Anthraxisrecognizedasanoccupational

disease.

Dermal,primaryinhalational,andintestinalanthraxaredifferentiated

basedonthepathogen’sportalofentry.Indermalanthrax,whichaccounts

for 90 – 95 %ofhumanB.anthracisinfections)thepathogensenterthrough

injuriesintheskin.Alocalinfectionfocussimilartoacarbuncledevelops

withintwotothreedays.Asepsiswithafoudroyant(highlyacute)course

maythendevelopfromthisprimaryfocus.Inhalationalanthrax(bioterrorist

anthrax),withitsunfavorableprognosis,resultsfrominhalationofdustcon-

tainingthepathogen.Ingestionofcontaminatedfoodscanresultinintestinal

anthraxwithvomitingandbloodydiarrheas.

Diagnosis.Thediagnosticprocedureinvolvesdetectionofthepathogenin

dermallesions,sputum,and/orbloodculturesusingmicroscopicandcultur-

ingmethods.

Therapy.TheantimicrobialagentofchoiceispenicillinG.Doxycycline(atet-

racycline)orciprofloxacin(afluoroquinolone)arepossiblealternatives.Sur-

geryiscontraindicatedincasesofdermalanthrax.

Epidemiologyandprophylaxis.AnthraxoccursmainlyinsouthernEurope

andSouthAmerica,whereeconomicdamageduetofarmanimalinfectionsis

considerable.Humanscatchthediseasefrominfectedanimalsorcontami-

natedanimalproducts.Anthraxisaclassiczoonosis.

Prophylaxisinvolvesmainlyexposurepreventionmeasuressuchasavoid-

ingcontactwithdiseasedanimalsanddisinfectionofcontaminatedproducts.

Acell-freevaccineobtainedfromaculturefiltratecanbeusedforvaccine

prophylaxisinhigh-riskpersons.

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Kayser, Medical Microbiology © 2005 Thieme