Relative penicillin G resistance in Neisseria meningitidis and reduced affinity of penicillin-binding protein 3

Abstract

We examined clinical isolates of Neisseria meningitidis relatively resistant to penicillin G (mean MIC, 0.3 ,ug/ml; range, 0.1 to 0.7 ,ug/ml), which were isolated from blood and cerebrospinal fluid for resistance mechanisms, by using susceptible isolates (mean MIC, c0.06 ,ug/ml) for comparison. The resistant strains did not produce detectable I-lactamase activity, otherwise modify penicillin G, or bind less total penicillin.Penicillin-binding protein (PBP) 3 of the six resistant isolates tested uniformly bound less penicillin G in comparison to the same PBP of four susceptible isolates. Reflecting the reduced binding affinity of PBP 3 of the two resistant strains tested, the amount of 3H-labeled penicillin G required for half-maximal binding was increased in comparison with that of PBP 3 of the two susceptible isolates. We conclude that the mechanism of resistance in these meningococci relatively resistant to penicillin G was decreased affinity of PBP 3.Concurrent with an epidemic of meningococcal disease in Spain from 1978 to 1985, the National Reference Laboratory began surveillance which included screening for penicillin G susceptibility. Of 3,264 strains isolated from blood or cerebrospinal fluid during those years, only one resistant isolate was observed in the final year (12). Subsequently, in the first six months of 1986, 9 (5%) of 168 invasive isolates were found to be relatively resistant to penicillin G. More worrisome is the decreased susceptibility of these strains to other P-lactams (2). The emergence of relatively penicillin-Gresistant strains in a short period of time suggests the possibility of a mutational event and dispersion of a clone or acquisition of a mobile genetic element harboring resistance. We sought to define the mechanism of resistance in these straihs. Possibilities include the production of ,B-lactamase, other enzymatic modification of the penicillin G molecule, acqcuisition of relative impermeability to penicillin G, or insensitivity of the cellular targets, the penicillin-binding proteins (PBPs). Each mechanism has different implications as to the activity of alternative antibiotics against these strains. MATERIALS AND METHODSStrains. All 16 resistant (defined as those growing on media containing 0.1 jig of penicillin G per ml) strains were isolated from cerebrospinal fluid or blood during 1985 and 1986 in Spain and were identified as Neisseria meningitidis by standard methods (9); 11 were serogroup B, 4 were serogroup C, and 1 was autoagglutinable. Twelve strains identified as susceptible (no growth on media containing 0.1 jig of penicillin G per ml) isolated in the same geographic area of Spain were used for comparisons; 8 were serogroup B, and 4 were serogroup C. All strains were stored in 50% tryptic soy broth (Difco Laboratories, Detroit, Mich.) containing 10% glycerol at -70°C.Enzymatic modification. P-Lactamase activity was sought by two methods; the rapid acidimetric assay with penicillin * Corresponding author. G (Sigma Chemical Co., St. Louis, Mo.) as substrate and phe...

Horizontal transfer of penicillin-binding protein genes in penicillin-resistant clinical isolates of Streptococcus pneumoniae.

“…The emergence of penicillin resistance by the development of penicillinresistant PBPs has been documented in Neisseria gonorrhoeae (23), Neisseria meningitidis (24), Haemophilus influenzae (25), and Staphylococcus aureus (26), in addition to S. pneumoniae. Interestingly all of these bacterial species, except Staphylococcus aureus, are naturally transformable, and, in those that have been examined [N. gonorrhoeae (27), N. meningitidis (29), and S. pneumoniae], the development of penicillin-resistant PBPs appears to have occurred not by mutation and selection, but by the introduction of a homologous PBP from a closely related species.…”

Correlation between Alterations of the Penicillin-binding Protein 2 and Modifications of the Peptidoglycan Structure in Neisseria meningitidis with Reduced Susceptibility to Penicillin G

“…Meningococcal strains that are highly resistant to penicillin G (MIC Ͼ 1 g/ml) due to the production of a plasmid-encoded ␤-lactamase have been detected in some countries (5)(6)(7)(8). However, meningococcal strains with reduced susceptibility to penicillin G (Pen I ) (MICs between 0.125 and 1 g/ml) have been reported worldwide (9), and this reduction in susceptibility is at least partly due to the decreased affinity of PBP2 encoded by an altered penA gene (10,11). N. gonorrhoeae also shows increased resistance to penicillin G due to the decreased affinity of both PBP1 and PBP2 for penicillin G combined with alterations of the gonococcal porin and the overexpression of the MtrCDE efflux pump (12).…”

Beta-lactamase plasmids and chromosomally mediated antibiotic resistance in pathogenic Neisseria species

“…In the 1980s plasmid-mediated resistance to tetracycline was characterized in gonococci for the first time (56). Trends in antimicrobial resistance in N. gonorrhoeae have recently been mimicked by other pathogenic Neisseria species (8,47). The possibility that increasing numbers of N. meningitidis isolates will acquire plasmid-mediated resistance to penicillin is of great medical concern.…”