Bacterial interference of Neisseria gonorrhoeae by alpha-haemolytic streptococci

Fifty pharyngeal isolates of alpha-haemolytic streptococci were tested against 20 cervical isolates of Neisseria gonorrhoeae for bacterial interference in vitro using the lawn-spotting method. Forty-seven (94%) isolates of streptococci showed inhibitory activity toward N gonorrhoeae, although nine of these were inhibitory to only one isolate of N gonorrhoeae. Isolates of N gonorrhoeae varied widely in their sensitivity to streptococci; the most sensitive were inhibited by 40 isolates of streptococci and the least sensitive by only 14 isolates. Species of Streptococcus found to inhibit growth of N gonorrhoeae were S mitis, S MG intermedius, S sanguis II, S mutans, and S morbillorum.