No, E. coli is not acid-fast.
According to the provided reference, E. coli is characterized as:
- Gram-negative
- Straight, rod-shaped bacilli
- Non-sporing
- Non-acid fast
The reference also notes that E. coli cells typically measure 1–3 μm in length and 0.4–0.7 μm in width. They usually exist as single cells or in pairs.
The acid-fast stain is a differential stain used to identify bacteria with a cell wall containing mycolic acid, such as *Mycobacterium* species. Since *E. coli* lacks this feature, it does not retain the primary dye carbolfuchsin after decolorization with acid-alcohol, therefore it is considered non-acid fast.
