: a bacterium (especially genus Corynebacterium) that resembles the bacterium of diphtheria but does not produce diphtheria toxin
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Daniel C. Schlenoff, Scientific American, 1 Jan. 2020
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Adjective
Among the germs were colon bacilli, staphylococci, streptococci, pneumococci and diphtheroid bacilli.
—Daniel C. Schlenoff, Scientific American, 1 Jan. 2020
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“Diphtheroid.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/diphtheroid. Accessed 31 Oct. 2025.
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diphtheroid
1 of 2 adjective
diph·the·roid
ˈdif-thə-ˌrȯid 
: resembling diphtheria
diphtheroid
2 of 2 noun
: a bacterium (especially genus Corynebacterium) that resembles the bacterium of diphtheria but does not produce diphtheria toxin
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