Systemic meningococcal isolates and meningococci from healthy pharyngeal carriers in Norway were screened for production of growth antagonistic substances. Seven (4.9%) of a total of 142 systemic strains and 3 (2.1%) of 140 carrier isolates spontaneously released diffusible growth antagonistic substances. Properties shown by these substances complied with the criteria used in the definition of a bacteriocin. A cluster of producers among systemic strains registered during the first half of 1975 in North Norway (13.5% of the isolates) was observed, coinciding with the peak in incidence of meningococcal disease of the Norwegian epidemic starting in that region. Among more recent isolates, producers occurred at approximately the same rate in systemic strains (2.5%) as in carrier isolates. The meningocin-producing isolates detected were either of serogroup A and generally sulfonamide-resistant, or serogroup B and sulfonamide-sensitive. The group A strains isolated from disease cases in North Norway during the first half of 1975 were mostly sulfonamide-resistant. Except for the producers, all these strains revealed distinctly higher sensitivity to meningocin than did serogroup B sulfonamide-resistant strains, which became predominant among meningococci causing disease in Norway from that time on.
Fate of Listeria monocytogenes on fully ripened Greek Graviera cheese stored at 4, 12, or 25 degrees C in air or vacuum packages: in situ PCR detection of a cocktail of bacteriocins potentially contributing to pathogen inhibition.
The behavior of Listeria monocytogenes on fully ripened Greek Graviera cheese was evaluated. Three batches (A, B, and C) were tested. Batches A and C were prepared with a commercial starter culture, while in batch B the starter culture was combined with an enterocin-producing Enterococcus faecium Graviera isolate. Cheese pieces were surface inoculated with a five-strain cocktail of L. monocytogenes at ca. 3 log CFU/cm2, packed under air or vacuum conditions, stored at 4, 12, or 25 degrees C, and analyzed after 0, 3, 7, 15, 30, 60, and 90 days. L. monocytogenes did not grow on the cheese surface, regardless of storage conditions. However, long-term survival of the pathogen was noted in all treatments, being the highest (P