Medical Microbiology

272 4 BacteriaasHumanPathogens

Nocardia...........................................................

Occurrence.ThegenusNocardiaincludesspecieswithmorphologysimilarto

thatoftheactinomycetes,differingfromtheminthatthenaturalhabitatof

theseobligateaerobesisthesoilanddampbiotopes.Thepathogensknown

forinvolvementinnocardioses,agenerallyveryraretypeofinfection,in-

cludeN.asteroides,N.brasiliensis,N.farcinia,N.nova,andN.otitidiscaviarum.

Morphologyandculture.NocardiaareGram-positive,fine,pleomorphic

rodsthatsometimesshowbranching.Theycanbeculturedonstandardnu-

trientmediumsandproliferateparticularlywellat 308 C.Nocardiaareobli-

gateaerobes.

Pathogenesisandclinicalpicture.Nocardiapenetratefromtheenvironment

intothemacroorganismviatherespiratorytractordermalwounds.Anin-

fectiondevelopsonlyinpatientswithpredisposingprimarydiseasesdirectly

Table4. 5 InfectionsCausedbyNontuberculousMycobacteria

Disease Frequentspecies Rarespecies

Chronicpulmonary

disease(adults)

M.kansasii

M.avium/M.intracellulare

(M.aviumcomplex)

M.abscessus

M.malmoense

M.xenopi

M.scrofulaceum

M.fortuitum

M.chelonae

andothers

Locallymphadenitis

(children,adolescents)

M.aviumcomplex M.kansasii,

M.malmoense

M.fortuitum

Skinandsofttissue

infections

M.marinum

M.fortuitum

M.chelonae

M.ulcerans

M.haemophilum

M.smegmatis

M.hansasii

Bone,joint,tendon

infections

M.kansasii

M.aviumcomplex

M.fortuitum

M.abscessus

M.smegmatis

M.chelonae

M.marinum

M.malmoense

Disseminateddiseases

inimmunocompromised

patients

M.kansasii

M.aviumcomplex

M.fortuitum

M.chelonae

M.genavense

M.xenopiandothers

4

Kayser, Medical Microbiology © 2005 Thieme