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Molecular characterization of the integrons in Shigella strains isolated from patients with traveler's diarrhea

M M Navia1, J Ruiz, J Vila

  • 1Servei de Microbiologia, Institut Clínic Infeccions i Immunologia, Hospital Clínic-IDIBAPS, University of Barcelona, Villarroel, 170, 08036 Barcelona, Spain.

Diagnostic Microbiology and Infectious Disease
|March 17, 2004
PubMed

Insights

Class 1 integrons were found in 13.25% of Shigella strains causing traveler's diarrhea. Researchers identified nine integrons and ten gene cassettes, noting a high prevalence of trimethoprim and aminoglycoside resistance genes.

Area of Science:

  • Microbiology
  • Genetics
  • Antimicrobial Resistance

Background:

  • Shigella species are a common cause of bacterial dysentery, particularly traveler's diarrhea.
  • Integrons, especially Class 1 integrons, are mobile genetic elements that play a significant role in the dissemination of antimicrobial resistance genes.
  • Understanding the prevalence and characteristics of integrons in Shigella is crucial for monitoring and combating antibiotic resistance.

Purpose of the Study:

  • To determine the prevalence and characterize Class 1 integrons in Shigella strains isolated from traveler's diarrhea patients.
  • To identify the specific gene cassettes within the detected integrons and their associated antibiotic resistance profiles.
  • To compare the observed integron prevalence with the known plasmid-mediated gene transfer capabilities of Shigella.

Main Methods:

  • Isolation and identification of Shigella strains from patient samples.
  • Screening for the presence of Class 1 integrons using molecular methods.
  • Characterization of integrons and associated gene cassettes through techniques like PCR and sequencing.
  • Analysis of antimicrobial resistance patterns in the studied strains.

Main Results:

  • A low prevalence of Class 1 integrons (13.25%) was detected among the 83 Shigella strains examined.
  • Nine distinct Class 1 integrons were identified in 11 multidrug-resistant strains.
  • A total of 10 different gene cassettes were found, conferring resistance to trimethoprim (dfrA genes), aminoglycosides (aadA genes), and beta-lactam antibiotics (oxa2).
  • A high frequency of dfr and aad gene cassettes was observed, indicating a significant role in resistance to these drug classes.

Conclusions:

  • The study found a lower-than-expected prevalence of Class 1 integrons in Shigella strains from traveler's diarrhea.
  • Despite the low prevalence, the identified gene cassettes highlight the potential for Shigella to acquire and spread resistance mechanisms.
  • This finding contrasts with the known ability of Shigella to readily acquire and transfer plasmids, suggesting complex dynamics in integron dissemination within this pathogen.

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