Medical Microbiology

300 4 BacteriaasHumanPathogens

OtherVibrioBacteria..................................

Vibrioparahemolyticusisahalophilic(salt-friendly)speciesfoundinwarm

oceanshallowsandbrackishwater.Thesebacteriacancausegastroenteritis

epidemics.Thepathogenistransmittedtohumanswithfood(seafood,raw

fish).Theillnessistransientinmostcasesandsymptomatictherapyissuffi-

cient.

Vibriovulnificusisanotheraquaticorganismthatproducesaverysmall

numberofsepticinfections,mainlyinimmunosuppressedpatients.

AeromonasandPlesiomonas..........................

Thebacteriaofthesetwogeneraliveinfreshwaterbiotopes.Somearecap-

ableofcausinginfectioninfish(A.salmonicida).Theyareoccasionallyob-

servedascontaminantsofmoistpartsofmedicalapparatussuchasdialysis

equipment,vaporizers,andrespirators.Theycancausenosocomialinfections

inhospitalizedpatientswithweakenedimmunesystems.Casesofgastroen-

teritismayresultfromeatingfoodscontaminatedwithlargenumbersof

thesebacteria.

HaemophilusandPasteurella......................................

&ThemostimportantspeciesofPasteurellaceaefromthemedicalpointof

viewisHaemophilusinfluenzae.Thisisanonmotile,Gram-negativerodthatis

oftenencapsulated.Capsuleserovarbisthemainpathogenicform.H.influ-

enzaeisafacultativeanaerobethatrequiresgrowthfactorsX(hemin)andV

(NAD,NADP)initsculturemedium.H.influenzaeisatypicalparasiteofthe

respiratorytractmucosa.Itoccursonlyinhumans.Itcausesinfectionsofthe

upperandlowerrespiratorytractinindividualswithweakenedimmunede-

fensesandinchildrenundertheageoffourorfive.Invasiveinfections—me-

ningitisandsepsis—arealsoobservedinsmallchildren.Abetalactamase-

stablebetalactamantibioticisrequiredfortreatmentsincethenumberof

betalactamase-producingstrainsobservedisincreasing.Conjugatevaccines

inwhichthecapsulepolysaccharideiscoupledwithproteinsareavailablefor

prophylacticimmunization.Thesevaccinescanbeadministeredbeginningin

thethirdmonthoflife. &

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Kayser, Medical Microbiology © 2005 Thieme