Differentiation of Kingella denitrificans from Neisseria gonorrhoeae by growth on a semisolid medium and sensitivity to amylase.

All 239 strains of Neisseria gonorrhoeae tested for sensitivity to amylase-impregnated disks showed zones of growth inhibition ranging from 15 to 30 mm in diameter. None of 52 strains of Kingella denitrificans were inhibited by the same amylase test. In addition, all N. gonorrhoeae strains grew well on a gonococcal base medium supplemented with either IsoVitaleX (BBL Microbiology Systems) or Supplement B (Difco Laboratories), whereas K. denitrificans grew adequately only on the medium with IsoVitaleX. The addition of L-cysteine or cystine to the medium with Supplement B enhanced the growth of K. denitrificans.