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Testing the Role of Multicopy Plasmids in the Evolution of Antibiotic Resistance
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Testing the Role of Multicopy Plasmids in the Evolution of Antibiotic Resistance

Published on: May 2, 2018

[Ampicillin resistance mediated by the R plasmid in strains of Shigella flexneri]

M M Ramírez1, M Marrero, R J Monté

  • 1Instituto de Medicina Tropical Pedro Kouri.

Revista Cubana De Medicina Tropical
|January 1, 1994
PubMed

Insights

Most Shigella flexneri strains from a pediatric diarrheal disease outbreak showed ampicillin resistance. A common resistance plasmid was identified and successfully transferred to E. coli, confirming its role in ampicillin resistance.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Molecular Biology

Background:

  • Shigella flexneri is a significant cause of bacterial dysentery, particularly in children.
  • Antibiotic resistance in bacterial pathogens poses a growing global health threat.
  • Understanding the mechanisms of antibiotic resistance is crucial for effective treatment strategies.

Purpose of the Study:

  • To investigate ampicillin resistance patterns in Shigella flexneri strains isolated during a pediatric diarrheal disease outbreak.
  • To identify and characterize the genetic elements responsible for ampicillin resistance in these strains.

Main Methods:

  • Minimal inhibitory concentration (MIC) of ampicillin was determined for 40 Shigella flexneri isolates.
  • Resistance plasmid (R) extraction was performed on all isolated strains.
  • Plasmid purification and conjugation experiments were conducted using Escherichia coli HE 101 as a recipient.

Main Results:

  • 82.5% (33/40) of Shigella flexneri strains exhibited resistance to ampicillin at concentrations of 8-16 µg/mL.
  • A common resistance plasmid was identified in all resistant strains.
  • Successful transfer of ampicillin resistance to Escherichia coli HE 101 via the identified plasmid was demonstrated.

Conclusions:

  • High levels of ampicillin resistance are prevalent in Shigella flexneri strains causing pediatric diarrhea outbreaks.
  • A transferable resistance plasmid is a key mechanism mediating ampicillin resistance in these strains.
  • These findings highlight the need for continuous surveillance of antibiotic resistance in Shigella species.

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