Intrinsic penicillin resistance in penicillinase-producing Neisseria gonorrhoeae strains

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F Ikeda1

  • 1Department of Microbiology, Toho University School of Medicine, Tokyo.

Microbiology and Immunology
|January 1, 1990
PubMed

Insights

High ampicillin resistance in penicillin-resistant Neisseria gonorrhoeae (PPNG) is linked to both beta-lactamase plasmids and intrinsic strain resistance. Reduced outer membrane permeability contributes significantly to this resistance.

Area of Science:

  • Microbiology
  • Genetics
  • Pharmacology

Background:

  • Penicillin-resistant Neisseria gonorrhoeae (PPNG) strains exhibit high ampicillin resistance.
  • These strains commonly harbor a 4.5 megadalton plasmid responsible for beta-lactamase production.
  • PPNG strains can be classified based on susceptibility to dicloxacillin, indicating varying resistance mechanisms.

Purpose of the Study:

  • To investigate the mechanisms underlying high ampicillin resistance in PPNG.
  • To determine the role of the beta-lactamase-producing plasmid (pTMS1) and intrinsic strain factors in ampicillin resistance.
  • To explore the contribution of outer membrane permeability to ampicillin resistance in PPNG.

Main Methods:

  • Determining minimal inhibitory concentrations (MICs) of ampicillin for PPNG strains.
  • Classifying PPNG strains based on dicloxacillin susceptibility.
  • Transferring the pTMS1 plasmid via conjugation to susceptible and resistant gonococcal strains.
  • Assessing ampicillin susceptibility of transconjugants.

Main Results:

  • Ampicillin MICs for PPNG strains ranged from 1.56 to 200 µg/ml.
  • A correlation between beta-lactamase activity and ampicillin susceptibility was observed in dicloxacillin-susceptible strains, but not in resistant strains.
  • Transfer of pTMS1 increased ampicillin resistance by 32-fold in susceptible strains and 128-fold in strains with chromosomal mutations.

Conclusions:

  • High ampicillin resistance in PPNG involves both plasmid-mediated beta-lactamase production and intrinsic resistance mechanisms.
  • Reduced outer membrane permeability appears to be a key factor contributing to the significant ampicillin resistance observed in PPNG.

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