Medical Microbiology

278 4 BacteriaasHumanPathogens

carrierstoeliminatethisreservoir,wherebyminocylinorrifampicinmustbe

usedinsteadofpenicillinG.Prophylacticimmunizationcanbeachieved

withavaccinemadefromthepurifiedcapsulepolysaccharidesA,C,Y,

andW-135.ThereisnoserogroupBvaccine,sincethecapsuleinserogroup

Bconsistsofpolyneuraminicacid,whichtheimmunesystemdoesnotrecog-

nizeasaforeignsubstance.

MoraxellaandAcinetobacter..........................

Thetaxonomicdefinitionsofthesegeneraarestillinconclusive.Bergey’s

ManualofSystematicBacteriologygroupsbothunderthefamilyMoraxella-

ceae.Thesebacteriaareshort,roundedrods,oftencoccoid,sometimesalso

diplococcoid.Theirnaturalhabitatiseitherhumanmucosa(Moraxella)orthe

naturalenvironment(Acinetobacter).

&Moraxella.Thegenuscomprisestwomedicallyimportantspecies:

— Moraxellacatarrhalis.Componentofthenormalfloraoftheupperre-

spiratorytract.Mayberesponsiblefor:pneumonia,acuteexacerbation

ofchronicbronchitis,otitismedia(upto 20 %inchildren),andsinusitis.

About 90 %ofallstrainsproduceoneoftheso-calledBROpenicillinases,so

thattherapywithapenicillinase-stablebetalactamantibioticisindicated.

— Moraxellalacunata.FormerlyDiplobacteriumMorax-Axenfeld.Cancause

conjunctivitisandkeratitis.Thereasonwhythisorganismisnowrarely

foundasapathogenintheseeyeinfectionsisunknown.

&Acinetobacter.Inimmunodeficientpersons,A.baumannii,A.calcoaceti-

cus,andotherspeciescancausenosocomialinfections(urinarytractinfec-

tions,pneumonias,woundinfections,sepsis).Clinicalstrainsofthesespecies

oftenshowmultiresistancetoantibiotics,sothattreatmentoftheseinfec-

tionsmayprovedifficult.

Enterobacteriaceae,Overview......................................

&ThemostimportantbacterialfamilyinhumanmedicineistheEnterobac-

teriaceae.Thisfamilyincludesgeneraandspeciesthatcausewell-defined

diseaseswithtypicalclinicalsymptoms(typhoidfever,dysentery,plague)

aswellasmanyopportuniststhatcausemainlynosocomialinfections(urin-

arytractinfections,pneumonias,woundinfections,sepsis).Enterobacteria-

ceaeareGram-negative,usuallymotile,facultativelyanaerobicrodbacteria.

Thehighlevelsofmetabolicactivityobservedinthemaremadeuseofin

identificationprocedures.Thespeciesaresubdividedintoepidemiologically

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Kayser, Medical Microbiology © 2005 Thieme