Penicillin-resistant (penr) clinical isolates of Neisseria meningitidis, which do not produce beta-lactamase, were first identified in Spain in 1985; the frequency of their recovery, which has been increasing in the past few years, reached 20% in 1989. Serogrouping, determination of serotypes and subtypes, and multilocus enzyme electrophoresis of the penr strains showed an extensive diversity. Resistance is due, at least in part, to a decreased affinity of penicillin-binding protein (PBP) 2 for penicillin. Similar low-affinity forms of PBP 2 are also found in penr isolates of Neisseria lactamica, Neisseria polysaccharea, and Neisseria gonorrhoeae. Genetic transformation of an N. meningitidis type strain to low-level penicillin resistance with DNA from resistant meningococci and other Neisseria species resulted in transformants that possessed low-affinity forms of PBP 2. These altered forms of PBP 2 have been shown to arise from recombinational events that replace parts of the PBP 2 gene with the corresponding regions from the PBP 2 genes of commensal Neisseria species.

A 2-kilobase fragment containing the penicillin-binding protein 2 gene (penA) was amplified by using the polymerase chain reaction with DNA prepared from 35 penicillin-resistant strains of Neisseria meningitidis isolated in England, Ireland, and Spain (MICs, 0.16 to 1.28 ,ug of benzylpenicillin per ml) and from 10 penicillin-susceptible strains (MICs, c 0.04 ,ug of benzylpenicillin per ml). The penA genes were digested with HpaH or TaqYI; and the resulting fragments were end-labeled, fractionated on a polyacrylamide gel, and autoradiographed, to produce gene fingerprints. The fingerprints of the penA genes of the 10 penicillinsusceptible strains were identical. In contrast, the fingerprints of the penA genes of all but two of the penicillin-resistant strains differed markedly from those of the penicillin-susceptible strains. The altered penA genes of group B penicillin-resistant strains were very diverse, and 14 different fingerprints were found among the 15 strains that we examined. The penA genes of the 19 resistant group C strains were less diverse, and two major fingerprint patterns predominated.