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