Activity of bacteriocin-like agents from Neisseria meningitidis on strains isolated from patients and carriers.

Strains of Neisseria meningitidis isolated from patients were more often completely insensitive to five bacteriocin-like agents than carrier strains, but no particular bacteriocin type could be associated with patient strains. Two genetically distinct types of insensitivity could be separated by transformation. Insensitivity to four bactericidal agents (from the strains P201, P213, P241 and 99/79) was caused by one common genetic marker whereas insensitivity to a bacteriostatic agent (from the strain 77/79) was caused by another.

Inhibitory spectrum of bacteriocin-like agents from Neisseria meningitidis.

Bacteriocin-like agents from five strains of Neisseria meningitidis were active against other meningococci and some other Neisseria species. Meningococci belonging to the same serogroup or serotype could be subdivided into distinct bacteriocin types. Insensitivity to the inhibitory agents was observed more frequently among serologically groupable strains than among non-groupable.

Influence of blood cells on the expression of bacteriocin-like activity in Neisseria meningitidis.

The inhibitors responsible for the bactericidal activity found in four strains of Neisseria meningitidis were strongly bound to or inactivated by blood cells. The bactericidal effects were specifically influenced by human cells of types O, A, B and AB. Cells from horse, sheep and rabbit had no significant effect.

Expression of bacteriocin-like activity in batch cultures of Neisseria meningitidis and consequences for genetic recombination.

The bactericidal activity found in four strains of Neisseria meningitidis and the bacteriostatic effect observed in one were expressed in the exponential phase of batch cultures and continued during the stationary phase. The active material was stable for more than 50 hours in agar media. In mixed cultures a strain with inhibitory activity eradicated a sensitive strain, and dominated the culture in the latter part of the exponential phase.

Three types of growth inhibition among strains of Neisseria meningitidis isolated from patients in Norway.

A survey has been made of Neisseria meningitidis strains isolated from patients in order to determine the prevalence of diffusible growth inhibitory substances active against other meningococci. Three types of growth inhibitory activity could be distinguished. The first type was release in cultures of nearly all strains after treatment with chloroform vapour.