Vancomycin hypersusceptibility in Neisseria gonorrhoeae isolated from patients involves diverse mutations

Abstract

We investigated the genetic determinants of hypersusceptibility to vancomycin and erythromycin found in Neisseria gonorrhoeae strains isolated from patients. In terms of resistance (highest concentration of antibiotic permitting growth), the levels of vancomycin resistance of six strains ranged from 0.2 to 1.0 ,ug/ml, and the level of erythromycin resistance of these strains was 0.02 or 0.05 ,ug/ml. DNA from these strains was used to introduce their hypersusceptibility determinants into partially isogenic derivatives of N. gonorrhoeae 89 which initially had wild-type levels of resistance to vancomycin (.3.0 ,ug/ml) and erythromycin (.0.1 ,ug/ml). The recombination frequencies found in reciprocal transformation tests of six isogenic strains indicated that the mutations responsible for vancomycin hypersusceptibility were located at different sites. The transformants selected for increased resistance to vancomycin were also resistant to erythromycin. This evidence, together with DNA concentration-response curves, indicated that the mutations affected either one gene locus or closely linked loci. The recombination indices obtained in crosses between our hypersusceptible strains and DNAs from reference strains carrying the envelope mutations env-l, env-2, env-3, and env-10 showed that the mutation (designated env-12) responsible for erythromycin hypersusceptibility in one strain (89-954) was located in close proximity to env-2. The determinant of vancomycin hypersusceptibiity in strain 89-954 was distinct from env-12, but the two were linked. In the other five isogenic strains, the hypersusceptibilities to both vancomycin and erythromycin could be annulled by spontaneous mutations in a locus provisionally designated vel because of its likely effects on the envelope. Vel+ mutants obtained by selection with either vancomycin alone or erythromycin alone gained increased resistance to both antibiotics.

Arginine-, hypoxanthine-, uracil-requiring isolates of Neisseria gonorrhoeae are a clonal lineage within a non-clonal population

“…If they also grow slowly in uiuo, this could influence the rate at which diversification of these strains occurs by recombination, as they would be rapidly Koelbl & Catlin, 1986). Failure to detect gonococci may result in failure to prescribe antibiotics, leading to continued infection and increased transmission of these strains to new hosts.…”

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

“…Similarly, a combination of tet, penB, and mtr genes produces a 16-fold increase in tetracycline MICs (68). A number of loci (e.g., env, mom, and vel) act to suppress mutations in mtr or increase susceptibility to antimicrobial agents such as vancomycin or erythromycin (env, vnc, and vet) (39,62). Other linked genes (spc, str, chl,fus, and rif [ Table 1]) include loci for resistance to antibiotics which affect ribosomal proteins (11,68,70).…”

Mutation in a locus linked to penB-nmp causes suppression of the Mtr phenotype of Neisseria gonorrhoeae

“…Additionally, mtr and penB mutations confer nonspecific resistance to certain other antibiotics (15,16,20). In contrast, mutations of env and vel loci, which affect the gonococcal envelope, cause atypically high susceptibility to certain hydrophobic antibacterial agents (11,13,14,17). The action of an env mutation in cells carrying mtr results in the phenotypic suppression of the effects of mtr and the acquisition of hypersusceptibility to various agents, including erythromycin and novobiocin (9,18).…”

“…The mom-2 mutation and the novel protein I seroreaction profile (00+00/+ +000+) arose in a Tetr transformant derived in a cross between DNA from a clinical strain, MHD2900 (13), and a recipient (strain 89-775) with wild-type penicillin resistance; an Spcr transformant, 89-1335 (mtr mom-2), introduced mom-2 and the nmp allele into transformant 89-1503. The mom4 mutation and the novel protein When subculturing the strains, care was taken to pick transparent P' colonies typical of piliated gonococci in order to preserve competence for transformation (13).…”

“…GCMBS agar is GC medium base (Difco Laboratories, Detroit, Mich.) with 1% White-Kellogg supplement (4). The defined fluid for transformation (DEFT) was described earlier (13). Inoculated media for transformation tests and for determinations of resistance were incubated at 36°C in an atmosphere of air plus 8% carbon dioxide.…”