Laboratory and clinical evaluation of modified New York City medium (Henderson formulation) for the isolation of Neisseria gonorrhoeae.

The growth-promoting properties of several ingredients of New York City (NYC) medium were investigated by using 100 recently isolated clinical strains of Neisseria gonorrhoeae. Difco GC medium base promoted the growth of large colonies of gonococci significantly better than other commercial GC medium bases. A 1% agar concentration resulted in the growth of larger colonies than 2% agar, without affecting the stability of the gel. Neither replacement of horse plasma with horse serum nor reducing the concentration of added serum from 12 to 3% affected the growth of even the most fastidious strains tested. From these observations, a modified NYC medium (Henderson) has been formulated which is easy to prepare and less expensive than NYC or Thayer-Martin medium. In a direct clinical comparison with 1,275 specimens, an isolation rate of 6.5% was achieved with both NYC medium and the Henderson formulation.