What is the significance of the 'molar teeth' appearance on blood agar?

The 'molar teeth' appearance on blood agar is a characteristic morphological feature associated with the Actinomyces species, particularly Actinomyces israelii. This unique morphology results from the formation of colonies that resemble the shape and arrangement of molar teeth, often seen when these bacteria grow in a rich medium like blood agar.

Actinomyces species are anaerobic or microaerophilic, and they tend to form filamentous structures that can aggregate in such a way that they produce these distinctive colony appearances. This is clinically significant because it helps in identifying infections caused by Actinomyces, which are known to be involved in conditions like actinomycosis, a chronic granulomatous disease that can affect various body parts, including the jaw and thoracic cavity.

In a laboratory setting, recognizing the 'molar teeth' appearance aids microbiologists and clinicians in diagnosing infections more accurately, prompting appropriate treatment strategies based on the organism involved.