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Updated: Aug 16, 2026
Quasi-metagenomic Analysis of Salmonella from Food and Environmental Samples
Published on: October 25, 2018
Isolation and molecular characterization of quinolone resistant Salmonella spp. from poultry farms
B San Martín1, L Lapierre, C Toro
1Laboratorio de Farmacología Veterinaria, Facultad de Ciencias Veterinarias y Pecuarias, Universidad de Chile, Santa Rosa 11735, La Pintana, Santiago, Chile. bsmartin@uchile.cl
Abstract:
The antimicrobial susceptibility of 94 Salmonella strains isolated from different poultry farms in Chile (broiler and laggin hens) were analyzed by the dilution plates method. Thirty-nine of them were resistant to flumequine, nalidixic acid and oxolinic acid with MIC values higher than 64 microg/ml. These quinolone resistant strains were analyzed in order to determine the presence of mutations in the QRDR region of gyrA gene by AS-PCR-RFLP analysis. 51.3% of the strains showed mutations at codon Ser 83 and 41.0% showed mutations at codon Asp 87. No mutations were observed on codon Gly 81. These mutations were confirmed by sequenciation of one representative strain from different RFLP pattern. Likewise, no double mutations were observed. Over 90% of the quinolone resistant strains presented mutations at the QRDR region of the gyrA gene. Three phenotypically resistant strains did not show any mutations on the QRDR region of gyrA gene. However, other molecular resistant mechanism could be involve. This is the first study that demonstrate the emergency of quinolone and fluoroquinolone resistance in Chilean Salmonella strains isolated from poultry thus indicating the requirement of monitoring programmes in veterinary medicine.
Insights
Quinolone resistance is emerging in Chilean poultry Salmonella. Over 90% of resistant strains show gyrA gene mutations, indicating a need for veterinary monitoring programs.
Area of Science:
- Veterinary Microbiology
- Molecular Biology
- Antimicrobial Resistance
Background:
- Salmonella strains are frequently isolated from poultry farms.
- Antimicrobial resistance in Salmonella poses a significant threat to public health.
- Quinolones and fluoroquinolones are critical antimicrobial agents used in veterinary medicine.
Purpose of the Study:
- To investigate the antimicrobial susceptibility of Salmonella strains from Chilean poultry.
- To identify the prevalence and molecular mechanisms of quinolone resistance in these strains.
- To highlight the emergence of quinolone resistance in Chilean poultry Salmonella.
Main Methods:
- Antimicrobial susceptibility testing using the broth microdilution method.
- Analysis of quinolone resistance determining regions (QRDR) of the gyrA gene using Amplification Refractory Mutation System - Polymerase Chain Reaction - Restriction Fragment Length Polymorphism (ARMS-PCR-RFLP).
- Sequencing of representative strains to confirm mutations.
Main Results:
- Out of 94 Salmonella strains, 39 exhibited resistance to quinolones (flumequine, nalidixic acid, oxolinic acid).
- Mutations in the QRDR of the gyrA gene were detected in over 90% of quinolone-resistant strains, primarily at codons Ser 83 (51.3%) and Asp 87 (41.0%).
- Three resistant strains lacked gyrA mutations, suggesting alternative resistance mechanisms.
Conclusions:
- This study is the first to demonstrate the emergence of quinolone and fluoroquinolone resistance in Salmonella from Chilean poultry.
- The high prevalence of gyrA mutations underscores their role in quinolone resistance in this context.
- Continuous monitoring programs in veterinary medicine are essential to track and manage antimicrobial resistance.
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