Is Veillonella gram positive or negative?

Is Veillonella gram positive or negative?

• A. Positive
• B. Gram-variable
• C. Negative
• D. Cannot be determined

Answer: (C)

Gram staining hinges on cell wall structure. Veillonella are Gram-negative cocci, meaning they have a thin peptidoglycan layer and an outer membrane. During the stain, the decolorization step removes the purple dye from these thin-walled cells, and they take up the pink counterstain, so they appear Gram-negative under the microscope. This staining pattern is typical for Veillonella, not Gram-variable, and not indeterminate in standard conditions. Hence, the correct conclusion is that Veillonella is Gram-negative.

Gram staining hinges on cell wall structure. Veillonella are Gram-negative cocci, meaning they have a thin peptidoglycan layer and an outer membrane. During the stain, the decolorization step removes the purple dye from these thin-walled cells, and they take up the pink counterstain, so they appear Gram-negative under the microscope. This staining pattern is typical for Veillonella, not Gram-variable, and not indeterminate in standard conditions. Hence, the correct conclusion is that Veillonella is Gram-negative.