Unusual association of a plasmid with nalidixic acid resistance in an epidemic strain of Shigella dysenteriae type 1 from Asia

M. Musharraf Ashraf, Z. U. Ahmed, D. A. Sack

Research output: Contribution to journalArticle

Abstract

The association of a 20-MDa plasmid with nalidixic acid resistant (Nal(r)) strains of Shigella dysenteriae 1 has been examined. The plasmid, which is readily transferable, does not itself code for nalidixic acid resistance but offers a survival advantage to its host under nalidixic acid stress. The plasmid-containing cultures of S. dysenteriae 1 produced Nal(r) mutants in vitro at a frequency 1000-fold higher than their plasmidless parent strains, after two exposures to nalidixic acid. Using a similar procedure, mutants resistant to other antibiotics such as chloramphenicol, tetracycline, or ciprofloxacin could not be isolated. The genome of S. dysenteriae 1 appears to carry a heavy load of the insertion sequence IS1. The propensity of the plasmid-containing strains to readily mutate to nalidixic acid resistance and its possible relevance to the observed association of the plasmid with Nal(r) clinical isolates is discussed.

Original languageEnglish (US)
Pages (from-to)59-63
Number of pages5
JournalCanadian Journal of Microbiology
Volume37
Issue number1
DOIs
StatePublished - 1991
Externally publishedYes

Keywords

  • Nalidixic acid
  • Plasmid
  • Shigella
  • Shigellosis

ASJC Scopus subject areas

  • Microbiology
  • Immunology
  • Applied Microbiology and Biotechnology
  • Molecular Biology
  • Genetics

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