Medical Microbiology

276 4 BacteriaasHumanPathogens

Therapy.TheagentofchoiceusedtobepenicillinG.Inrecentyears,however,

thepercentageofpenicillinase-producingstrainshasincreasedconsiderably

allovertheworld.Forthisreason,third-generationcephalosporinsarenow

usedtotreatuncomplicatedcasesofgonorrhea.Theyareappliedinasingle

dose(e.g.,ceftriaxone, 250 – 500 mgi.m.).Goodresultshavealsobeenre-

portedwithsingle-doseoralapplicationoffluorinated4-quinolones(e.g.,

0.5gciprofloxacinor0.4gofloxacin).

PenicillinResistanceinGonococci

Thedeterminantsofhigh-levelpenicillinresistanceingonococciaresmall,noncon-

jugativeplasmids,whicharemobilizedbyaconjugativehelperplasmidfortrans-

missionfromonegonococcalcelltoanother.Thepenicillinresistanceplasmids

codefortheTEMbetalactamasethatoccursfrequentlyinEnterobacteriaceae.It

isthereforeassumedthatthepenicillinasegeneingonococciderivedfromtheEn-

terobacteriaceaegenepool.Low-level,inherentresistancetopenicillinisbasedon

chromosomalgenes(penA,penB)thatcodeforpenicillin-bindingproteinswithre-

ducedaffinitytopenicillin.Thesegenesareproductsofmutations.

Epidemiologyandprevention.Gonorrheaisaworldwidesexuallytrans-

mitteddiseasethatoccursonlyinhumans.Itslevelofannualincidencein

developedcountriesisestimatedat 12 casesper 1000 inhabitants.Theactual

figuresarelikelytobemuchhigherduetolargenumbersofunreportedcases.

AreductioninincidenceseeninrecentyearsmaybeduetoAIDSprophylaxis.

Protectiveimmunizationforhigh-riskpersonsisnotfeasibleduetotheanti-

genvariabilityoftheorganismasdescribedabove.Stoppingthespreadof

gonorrheainvolvesmainlyrapidrecognitionofinfectionsandtreatmentac-

cordingly.

Onehundredpercentpreventionofophthalmianeonatorumispossible

withasingleparenteraldoseof 125 mgceftriaxone.Localprophylaxisis

alsopracticedusinga 1 %solutionofsilvernitrateoreyeointmentscontain-

ing 1 %tetracyclineor0.5%erythromycin.

Neisseriameningitidis(Meningitis,Sepsis)...........

Morphologyandculture.MeningococciareGram-negative,coffee-bean-

shapedcoccithatarefrequentlypleomorphicandhaveadiameterof 1 lm

(Fig.4. 16 b).Theyarenonmotileandfeatureapolysaccharidecapsule.

Growingmeningococciinculturesrequiresmediumscontainingblood.

Aconcentrationof 5 – 10 %CO 2 encouragesproliferation.

Antigenstructure.SerogroupsA,B,C,D,etc.(atotalof 1 2)aredifferentiated

basedonthecapsulechemistry.Epidemicsarecausedmainlybystrainsof

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Kayser, Medical Microbiology © 2005 Thieme