Question abt Corynebacterium diphtheriae - regarding suppression of growth (Oct/11/2009 )

Hi. I'm having trouble regarding the growth of C. diphtheriae on HBA. I received a mixed culture containing C. diphtheriae with S. pneumoniae. When I cultured it on HBA, only like 1 or 2 super tiny colonies of C diphtheriae were found. When I cultured the colony on another fresh HBA, no colonies were seen but when I did a gram stain on the 'empty' HBA plate, there were C. diphtheriae see.

Any idea why this happened? I remember hearing something about C. diphtheriae being suppressed when grown with S. pneumoniae. Is this true and why?

Thanks.

What is HBA?

Have you no tellurite agar? Loeffler's?