The modified GC medium (MGC) was developed for identification of beta-hemolytic group B streptococci. This medium was developed on the basis of enhancingñpigment production of group B streptococci. Three hundred and thirty isolates were tested including 180 isolates of beta-hemolytic group B streptococci, 102 isolates of beta-hemolytic non-group B streptococci, and 48 isolates of Enterococcus faecalis. All isolates of group B streptococci gave carotenoid pigment by this medium. On the other hand, all of non-group B streptococci and E. faecalis did not show pigment after 72 h incubation. The specificity and sensitivity of MGC was 100 %. There were no false positive and false negative in this medium. The MGC may be the alternative of choice for the presumptive identification of group B streptococci.

Keywords: MGC, Carotenoid pigment, Group B streptococci, GBS, Streptococcus lactiae, beba-hemolytic
streptococci