What does Gram variable mean and why does it happen?

Question

If you know of any websites that can provide a definition and backgroud information I would really appreciate it.

Answer 1

Gram variable means that the bacterium under question stains sometimes like a gram + organism, and sometimes like a gram -.

There are several possibilities of what's going on... damage to the cell wall, either physical or through autolysis (Strep. pneumoniae is one I recall with an autolysis issue).  Age of culture is important, as is what it's suspended in.  And then there are organisms that have capsules, or are recalcitrant growers, like many of the Mycobacterium species.  Gummy growers that want to make thick smears often appear to be gram variable, like the ropy root beer bug, Leuconostoc mesenteroides.  Direct smears from someone being treated with an antibiotic also often produces odd gram staining results that can send you down the primrose path to a wrong id.

http://findarticles.com/p/articles/mi_m3...

You might try asking this question in a group with a number of microbiologists -- I'm sure someone with more current bacterial physiology classes than I (mine were 30+ years ago) can help more.