Neisseria gonorrhoeae identification in carbohydrate medium containing guinea pig serum

Clinical isolates of Neisseria gonorrhoeae from Manitoba were tested for their carbohydrate degradation activity in Cystine Trypticase Agar (C.T.A) medium, Mueller-Hinton Agar and guinea pig serum agar. Each isolate was tested using 2 carbohydrates (e.g. glucose and maltose) in the above three media. Out of 661 isolates tested, only 80% were positively identified in C.T.A. medium. Mueller-Hinton agar allowed 88% identification while guinea pig serum agar yielded 100% identification. In a second series of experiments, 102 cultures of N. gonorrhoeae were used to compare Flynn & Waitkins medium with guinea pig serum agar. Only 91 of these were identified with Flynn and Waitkins medium while guinea pig serum agar identified all the 102 isolates. Guinea pig serum provides adequate growth of fastidious N. gonorrhoeae essential for detecting specific enzymes. Since guinea pig serum does not contain maltase activity, it does not interfere with the biochemical activities tested. Guinea pig serum agar is easy to prepare, does not require a heavy inoculum and gives definite color change in the medium.