Combining Staphylococcus aureus with acid-fast organisms like Mycobacterium smegmatis during the acid-fast staining technique serves several educational and analytical purposes.
First, the inclusion of a non-acid-fast organism such as Staphylococcus aureus provides a clear contrast against the acid-fast organism. This contrast is crucial because acid-fast staining is used specifically to identify bacteria that are resistant to decolorization by acids during staining. By including a non-acid-fast species, it becomes much easier to observe the staining differences under the microscope.
When subjected to the acid-fast stain, Mycobacterium smegmatis will retain the primary stain (such as carbol fuchsin) and appear bright pink or red, while Staphylococcus aureus will not retain the stain due to its cell wall composition, resulting in a blue or green color when counterstained (commonly with methylene blue). This obvious color distinction allows for effective visual confirmation of the technique’s accuracy and is especially useful in educational settings where students are learning to differentiate between various bacterial types.
Moreover, combining these two types of organisms enhances practice and experience for microbiologists. Understanding the staining patterns helps in the accurate identification and diagnosis of diseases caused by acid-fast bacteria, which are more commonly associated with pathogens such as Mycobacterium tuberculosis.
In summary, the combination of Staphylococcus aureus with Mycobacterium smegmatis in acid-fast staining is desirable for providing clear visual contrast, facilitating learning, and aiding in the identification of different bacterial types in laboratory settings.