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Updated: Aug 6, 2026

High-throughput Assay to Phenotype Salmonella enterica Typhimurium Association, Invasion, and Replication in Macrophages
Published on: August 11, 2014
[Resistance to antibiotics in Salmonella]
Antibiotic resistance in Salmonella strains has fluctuated since 1959. A ban on tetracycline in animal feed reduced resistance in pigs and humans, though multidrug-resistant strains emerged in calves.
Area of Science:
- Microbiology
- Antimicrobial Resistance
- Food Safety
Context:
- Longitudinal surveillance of Salmonella antibiotic resistance since 1959.
- Monitoring resistance to tetracycline, chloramphenicol, kanamycin, ampicillin, and trimethoprim.
- Investigating resistance trends in human and animal populations.
Purpose:
- To analyze trends in Salmonella antibiotic resistance over several decades.
- To assess the impact of regulatory changes (tetracycline ban in animal feed) on resistance patterns.
- To identify the emergence and spread of multidrug-resistant Salmonella strains.
Summary:
- Tetracycline resistance in human and pig Salmonella isolates increased from 1961.
- Following a 1974 ban on tetracycline in animal feed, resistance decreased in pigs and humans.
- Multidrug-resistant Salmonella strains, particularly S. typhimurium and S. dublin, increased in veal calves from 1972.
- Multidrug-resistant strains in humans were primarily linked to international adoption, with limited further spread observed.
Impact:
- Demonstrates the direct correlation between antibiotic use in animal feed and resistance in bacterial populations.
- Highlights the effectiveness of regulatory interventions in mitigating antimicrobial resistance.
- Identifies specific Salmonella serotypes and sources associated with multidrug resistance, informing public health strategies.
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