Table 1

Differential diagnoses of gram-positive branching rods

OrganismGrowth based on O2 requirementCatalase testAppearance on Ziehl-Neelsen test (Kinyoun method)
Nocardia spAerobicPositiveAcid fast
Rhodococcus spAerobicPositiveAcid fast
Gordonia spAerobicPositiveAcid fast
Tsukamurella spAerobicPositiveAcid fast
Streptomyces spAerobicPositiveNon-acid fast
Actinomadura spAerobicPositiveNon-acid fast
Dermatophilus spAerobicPositiveNon-acid fast
Nocardiopsis spAerobicPositiveNon-acid fast
Thermophilic actinomycesAerobicPositiveNon-acid fast
Actinomyces spObligate anaerobePositiveNon-acid fast
Cutibacterium propionicumFacultative anaerobeNegativeNon-acid fast
C. acnes phylotype IIIFacultative anaerobePositiveNon-acid fast
A. israeliiFacultative anaerobeNegativeNon-acid fast