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Characteristics of conjugative R-plasmids from pathogenic avian Escherichia coli
R E Wooley1, K R Spears, J Brown
1Department of Medical Microbiology, College of Veterinary Medicine, University of Georgia, Athens 30602.
Abstract:
Three of four virulent avian Escherichia coli isolates transferred a single large molecular-weight R-plasmid to two recipient E. coli strains. Antibiotic resistances transferred included streptomycin (two isolates) and streptomycin-tetracycline-sulfa (one isolate). Production of colicin and siderophores, complement resistance, and embryo lethality present in the virulent isolates were not transferred to recipient organisms. From the results, it appears that the R-plasmids of these virulent avian E. coli are not associated with virulence.
Insights
Virulent avian Escherichia coli transferred R-plasmids conferring antibiotic resistance to recipient strains. However, virulence factors like colicin production and embryo lethality were not transferred, suggesting R-plasmids are not linked to avian E. coli virulence.
Area of Science:
- Microbiology
- Bacterial genetics
- Avian pathogens
Background:
- Avian pathogenic Escherichia coli (E. coli) pose a significant threat to poultry health.
- Understanding the genetic basis of E. coli virulence and antibiotic resistance is crucial for effective disease management.
- R-plasmids are known to carry antibiotic resistance genes and can be transferred between bacterial strains.
Purpose of the Study:
- To investigate the role of R-plasmids in the virulence of avian E. coli isolates.
- To determine if specific virulence factors are co-transferred with antibiotic resistance genes on R-plasmids.
- To assess the association between R-plasmids and key virulence traits in avian E. coli.
Main Methods:
- Isolation and characterization of virulent avian E. coli strains.
- Plasmid transfer experiments using conjugation to recipient E. coli strains.
- Assessment of antibiotic resistance profiles before and after plasmid transfer.
- Evaluation of virulence factor transfer, including colicin production, siderophore production, complement resistance, and embryo lethality.
Main Results:
- Three of four virulent avian E. coli isolates successfully transferred a large R-plasmid to recipient strains.
- Transferred R-plasmids conferred resistance to streptomycin and a combination of streptomycin-tetracycline-sulfa.
- Crucially, virulence-associated traits such as colicin production, siderophore production, complement resistance, and embryo lethality were not transferred with the R-plasmids.
Conclusions:
- The R-plasmids studied in these virulent avian E. coli isolates are primarily associated with antibiotic resistance.
- The genetic determinants for the observed virulence factors in these strains appear to be located elsewhere on the chromosome or on different mobile genetic elements.
- These findings suggest that R-plasmid-mediated antibiotic resistance is not directly linked to the virulence of these specific avian E. coli isolates.