Some of which may be opportunistic pathogens. are usually called diphtheroids. These include:-
Some of these diphtheroids are short and ovoid in shape with a tendency to show polar staining with methylene blue but devoid of volutin granules as demonstrated by selective stains; other diphtheroids which may be present in respiratory secretions or purulent discharges from septic wounds, middle ear infections, etc., resemble Corynebacterium diphtheriae in their morphology and staining reactions, but usually ferment sucrose, and are non-toxigenic.
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