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(ˈdɪf θəˌrɔɪd, ˈdɪp-)

1. resembling diphtheria, esp. in the formation of a false membrane in the throat.
2. any bacterium, esp. of the genus Corynebacterium, that resembles the diphtheria bacillus but does not produce diphtheria toxin.
References in periodicals archive ?
To the Editor: Varibaculum cambriense is an anaerobic, gram-positive, diphtheroid bacterium that was described by Hall et al.
Due to numerous shared characteristics, Rhodococcus is commonly misidentified as diphtheroid contaminant and normal flora, Mycobacterium, Nocardia, Bacillus, Micrococcus organisms or even fungi (6).
Multiple urine cultures revealed staphylococci, streptococci, Escherichia coli, and diphtheroid bacillus species.
Even though it grows well on commonly used clinical laboratory media, it can be confused as a streptococcus or diphtheroid and may be missed by a novice microbiologist.
rhusiopathiae as a nonpathogenic Gram-positive bacillus, such as a diphtheroid skin contaminant, or as Bacillus or Clostridium species if identification is incomplete.
If, for example, a diphtheroid is isolated from a spinal fluid specimen, it would be important to rule out Listeria with a hanging drop motility test.