Medical Microbiology

274 4 BacteriaasHumanPathogens

pathogensincerebrospinalfluidandblood.Thediseaseoccurssporadically

orintheformofminorepidemicsinchildren,youths,andyoungadults.The

antibioticsofchoicearepenicillinGandthird-generationcephalosporins.

&

ThefamilyNeisseriaceaeincludesaerobic,Gram-negativecocciandrods

(seeTable3. 9 ,p.222),themostimportantofwhicharethehumanpathogens

N.gonorrheaeandN.meningitidis.OtherspeciesinthegenusNeisseriaare

elementsofthenormalmucosalflora.

Neisseriagonorrheae(Gonorrhea)....................

Morphologyandculture.GonococciareGram-negative,coffee-bean-shaped

coccithatareusuallypairedandhaveadiameterofapproximately 1 lm

(Fig.4. 16 ).Attachmentpilionthebacterialcellsurfaceareresponsiblefor

theiradhesiontomucosalcells.

Gonococcicanbegrownonmoistculturemediumsenrichedwithprotein

(blood).Theatmosphereforprimaryculturingmustcontain 5 – 10 %CO 2.

Pathogenesisandclinicalpicture.Gonorrheaisasexuallytransmitteddis-

ease.Thepathogenspenetrateintotheurogenitalmucosa,causingalocal

purulentinfection.Inmen,theprostateandepididymiscanalsobecomein-

fected.Inwomen,thegonococcicanalsocausesalpingitis,oophoritis,oreven

peritonitis.Gonococcireachingtheconjunctivalmembranemaycausea

purulentconjunctivitis,seenmainlyinnewbornchildren.Gonococcican

alsoinfecttherectalorpharyngealmucosa.Hematogenouslydisseminated

gonococcimayalsocausearthritisorevenendocarditis.

DeterminantsofthePathogenicityofGonococci

AttachmentpilionthesurfaceandtheoutermembraneproteinOpaarerespon-

sibleforadhesiontocellsoftheurogenitaltract.Opaalsodirectstheinvasionpro-

cessbymeansofendocytosis.Immunedefensesagainstgranulocytesarebasedon

theoutermembraneporinPorthatpreventsthephagosomefromfusingwithlyso-

somes,resultinginthesurvival—andproliferation—ofphagocytosedgonococciin

granulocytes.Thelipo-oligosaccharide(LOS)intheoutermembraneisresponsible

forresistancetocomplement(serumresistance)aswellasfortheinflammatory

tissuereactioninamanneranalogoustothemorecomplexlystructuredLPSof

enterobacteria.Gonococcicancaptureironfromthesiderophilicproteinslactofer-

rinandtransferrin,accumulatingitinsidethebacterialcellstofacilitatetheirrapid

proliferation.AnIgA 1 proteaseproducedbythegonococcihydrolyzessecretory

antibodiesinthemucosalsecretions.Thepronouncedantigenvariabilityoftheat-

tachmentpili(p. 1 4)andtheOpaproteinmakeitpossibleforgonococcitothwart

specificimmunedefensemechanismsrepeatedly.

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Kayser, Medical Microbiology © 2005 Thieme