PLASMID CARRIAGE AND ANTIBIOTIC SUSCEPTIBILITY OF NEISSERIA-MENINGITIDIS STRAINS ISOLATED IN SWEDEN 1981-1990

A random selection of Neisseria meningitidis strains isolated in Swede n in the period 1981-1990 were investigated for plasmid carriage and s usceptibility to antimicrobial agents commonly used for treatment and prophylaxis of meningococcal disease. The MICs were determined by the agar dilution method for penicillin V, penicillin G, rifampicin, sulfa diazine, erythromycin and tetracycline. In 13 % of the invasive strain s the MIC of penicillin V was greater-than-or-equal-to 0.5 mg/l which may cause concern regarding the usefulness of penicillin V in prophyla xis. In strains isolated from the urogenital tract the MICs of penicil lin V and penicillin G were higher than in the invasive strains. In ab out 82 % of the strains isolated in 1987-1988 the MIC of tetracycline was greater-than-or-equal-to 0.5 mg/l whereas no such strains were fou nd in 1981-1982. Plasmids were found in 2 of 119 invasive strains, in 1 of 50 strains from the respiratory tract and in 1 of 19 strains from the urogenital tract. The plasmid sizes were 1.3, 2.6, 25 and 40 Mda. None of these strains were beta-lactamase producing and no relation t o a high degree antibiotic resistance was observed.