Medical Microbiology

Mycoplasma 341

contrasttoallotherbacteria,mycoplasmaspossessnorigidcellwall.Flagel-

lae,fimbriae,pili,andcapsulesarelackingaswell.Duetotheirinherentplas-

ticity,mycoplasmasusuallyslipthroughfiltersthatholdbackotherbacteria.

Sincetheircellwallcontainsnomurein,mycoplasmasarecompletelyinsen-

sitivetoantibioticsthatinhibitmureinsynthesis(e.g.,betalactams).

Mycoplasmascanbeculturedonspecialisotonicnutrientmediums.After

twotoeightdays,smallcoloniesdevelopresemblingsunny-side-upeggsand

growingpartiallyintotheagar.

Pathogenesisandclinicalpictures.

&Infectionsoftherespiratoryorgans.ThepathogeninvolvedisM.pneu-

moniae.Theorganismistransmittedbyaerosoldroplets.Thecellsattach

themselvestotheepitheliaofthetrachea,bronchi,andbronchioles.The

mechanismsthatfinallyresultindestructionoftheepithelialcellsareyet

unknown.Theinfectiondevelopsintopneumoniawithaninflammatoryexu-

dateinthelumensofthebronchiandbronchioles.Theincubationperiodis

10 – 20 days.Theinfectionmanifestswithfever,headache,andapersistent

cough.Theclinicalpicturesoftheinfectioncourseisfrequentlyatypical,

i.e.,thepneumoniacannotbeconfirmedbypercussionandauscultation.

Adifferentialdiagnosismustalsoconsiderviralpneumonias,ornithosis,

andQfever.Sequelaecansetinduringorshortlyaftertheacuteinfection,

includingpericarditis,myocarditis,pancreatitis,arthritis,erythemanodo-

sum,hemolyticanemias,polyneuritis,andothers.

&Infectionsoftheurogenitaltract.TheseinfectionsarecausedbyM.ho-

minisandUreaplasmaurealyticum.Thesefacultativelypathogenicspecies

alsooccurinhealthypersonsaspartofthemucosalflora,sothattheiretio-

logicalrolewhenisolatedisoftenamatterofcontroversy.U.urealyticumis

consideredresponsiblefor 10 – 20 %ofcasesofnongonococcalurethritisand

prostatitisinmen.

Diagnosis.Thesepathogenscanbegrownonspecialculturemediums.Com-

merciallyamplificationtestsareavailablefordirectidentificationofM.pneu-

moniae.TheCFTwasformerlyusedtodetectantibodiestoM.pneumoniae;

todaythisisdonewithIgM-specificEIAs.Antibodytestsareofnodiagnostic

valueininfectionscausedbyM.hominisandU.urealyticum.

Therapy.Theantibioticsofchoicearetetracyclinesandmacrolides.M.homi-

nisshowsanaturalresistancetomacrolides,U.urealyticumtolincomycins.

Concurrentpartnertreatmentisrecommendedinurogenitalinfections.

Epidemiology and prevention. M. pneumoniae is found worldwide.

Humansaretheonlysourceofinfection.Thepathogensaretransmitted

bydropletinfectionduringclosecontact.Infectionsarefrequentlycontracted

infamilies,schools,homesforchildren,workcamps,andmilitarycamps.

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Kayser, Medical Microbiology © 2005 Thieme