Medical Microbiology

creasesandthepolartubule,whichisupto 100 lmlong,isextrudedrapidly.

Ifthetipofthepolartubulepenetratesthewallofanenterocyte,thespo-

roplasmmigratesthroughthehollowtubuleintothehostcell.TheMicro-

sporathenreproducelocallyinintestinalcells orinvadeotherorgans

fromthissite.Aerogenicinfectionsappearprobableinsomegenera.Inani-

mals,diaplacentaltransmissionofEncephalitozoonhasbeenconfirmed.

ItisnotentirelyclearbywhatmechanismstheMicrosporaaredissem-

inatedinthebody.Incellcultures,theparasitesareabletoinfectneighboring

tissuecellsbyextrudingtheirpolartubuleandinjectingthesporoplasminto

them.Invitro,Microsporaarephagocytosedbymacrophagesandotherhost

cells(so-callednonprofessionalphagocytes:epithelialandendothelialcells,

mesenchymalcells).Itisassumedthattheymaybetransportedwithinthe

bodyinsidesuchcells.

Clinicalmanifestations.Microsporaattainclinicalsignificancealmostexclu-

sivelyinimmunodeficientpersons,inparticularAIDSpatients.Thefollowing

listsummarizesthediseasescausedbytheindividualspeciestogetherwith

somediagnosticinformation.

&Enterocytozoonbieneusi

Occurrence:

Probablyworldwide,foundin 2 – 50 %ofHIVpatientswithchronicdiar-

rhea,withprevalenceshowingadownwardtrendsincethenewtypeofanti-

retroviraltherapywasintroduced.Rarelydiagnosedinimmunocompetent

persons.E.bieneusiwasalsofoundinthebiliaryepitheliumofmonkeys(ma-

caques)andinfecalsamplesofanimals,includingpigs,cattle,dogs,andcats.

ThespeciesE.bieneusiconsistsofnumberofvariousgenotypes.Current

knowledge suggeststhathumans acquire the infectionpredominantly

frominfectedpersons,whereastransmissionofgenotypesfromanimalsto

man—ifitoccursatall—isarareevent.

Localization:

Mainlyinthesmallintestine,inenterocytesatthetipsofvilli,lessfre-

quentlyinthecolonaswell,inthebileductsandgallbladder.Intracellular

localizationinplasmawithoutparasitophorousvacuole.Symptoms:chronic

diarrhea,alsowithcholangiopathy;asymptomaticinfectionsareknownto

occur.

Diagnosis:

Detectionoftinyspores(1. 1 – 1 .6!0.7–0.9lm)instainedstoolsmears.

Thesporeshavefourtosevenpolartubulewindingsinadoublerow(inother

species:singlerow!).

&Encephalitozoonintestinalis(formerlySeptataintestinalis).

540 9 Protozoa

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Kayser, Medical Microbiology © 2005 Thieme