Isolation and characterization of a bacteriophage specific for Neisseria perflava

Six isolates from normal throat samples have been shown to contain phage active against Neisseria perflava. The phage isolates were similar in terms of host range, latent period, burst size, antigenic properties, morphology, and nucleic acid content. Neutralization studies with antisera demonstrated that the isolates exhibited a very high degree of serological relatedness. These results taken together suggested that the isolates represented a single strain of bacteriophage. This phage, which we have designated NP-1, exhibited a high degree of host specificity, attacking only one of the several strains of N. perflava tested and none of the other species tested. One-step growth experiments yielded minimum latent periods of approximately 35 min; average burst sizes varied from 34 to 63 plaque-forming units per cell. Electron micrographs revealed particles with heads averaging 75 nm in diameter and tails averaging 300 nm in length and 18 nm in diameter. The phage contained double-stranded DNA with a guanine plus cytosine content of 38%.