Medical Microbiology

158 3 GeneralBacteriology

latedbacteriaaredescribedasmonotrichous,lophotrichous,orperitrichous,

dependingonhowtheflagellaarearranged(seeFig.3. 1 ,p. 14 7).Thebasal

bodytraversesthecellwallandcytoplasmicmembranetoanchortheflagel-

lum(seeFigs.3. 7 and3. 13 )andenablesittowhirlaboutitsaxislikeapro-

peller.InEnterobacteriaceae,theflagellarantigensarecalledHantigens.To-

getherwiththeOantigens,theyareusedtoclassifybacteriainserovars.

AttachmentPili(Fimbriae),ConjugationPili.........

ManyGram-negativebacteriapossessthinmicrofibrilsmadeofproteins(0. 1 –

1 .5nmthick, 4 – 8 nmlong),theattachmentpili.Theyareanchoredinthe

outermembraneofthecellwallandextendradiallyfromthesurface.Using

thesestructures,bacteriaarecapableofspecificattachmenttohostcellre-

ceptors(ligand—receptor,key—keyhole).

Theconjugationpili(syn.sexpili)inGram-negativebacteriaarerequired

fortheprocessofconjugationandthusfortransferofconjugativeplasmids

(seep. 1 75).

ExamplesofAttachmentPiliinGram-NegativeBacteria

PAP(syn.Ppili) Pyelonephritis-associatedpili.Bindtoreceptorsoftheuro-

epitheliumandtothePbloodgroupantigen(hence“P”pili).

Thespecificreceptorsforthesepiliareplentifulontheuro-

epithelialsurface.PAParecharacteristicoftheuropathological

varietyofEscherichiacolithatcausesspontaneousurinarytract

infectionsinpatientsshowingnotractobstruction.

CFA1,CFA2 Colonizationfactors.Piliresponsibleforspecificbindingofen-

teropathogeniccolibacteriatoenterocytes.

Gonococcal

attachmentpili

Usedforspecificattachmentofgonococcimucosalcellsofthe

urogenitalepithelium.

Biofilm.................................................

Abacterialbiofilmisastructuredcommunityofbacterialcellsembeddedina

self-producedpolymermatrixandattachedtoeitheraninertsurfaceorliving

tissue.Suchfilmscandevelopconsiderablethickness(mm).Thebacterialo-

cateddeepwithinsuchabiofilmstructureareeffectivelyisolatedfromim-

munesystemcells,antibodies,andantibiotics.Thepolymerstheysecreteare

frequentlyglycosides,fromwhichthetermglycocalyx(glycosidecup)forthe

matrixisderived.

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Kayser, Medical Microbiology © 2005 Thieme