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[Plasmid characteristics of Salmonella strains of various origins]
Abstract:
Salmonella antibiotic-resistant strains, isolated from patients with hospital infections and from various environmental objects, showed lower virulence than antibiotic-sensitive strains in experiments on mice infected by intraperitoneal and enteral routes. Salmonella strains, sensitive to antimicrobial preparations, contained 1-2 plasmids, while those with multiple drug resistance contained 3-10 plasmids varying in their molecular weight. All these strains, with the exception of one laboratory strain, carried a plasmid with a molecular weight of about 60 Md. A decrease in the virulence of Salmonella strains, carrying R-plasmid, with respect to mice, their natural host, in experimental infection by the above-mentioned routes was probably unrelated to the loss of this plasmid. 80% of Salmonella strains with multiple resistance to antibiotics yielded positive results in the keratoconjunctival and conjunctival tests as compared with 42% of sensitive strains. These data suggest that Salmonella strains, carrying R-plasmid, retained pronounced capacity for local colonization.
Insights
Antibiotic-resistant Salmonella strains exhibit reduced virulence in mice but retain colonization capacity. This suggests R-plasmid carrying strains may pose different infection risks.
Area of Science:
- Microbiology
- Infectious Diseases
- Genetics
Background:
- Antibiotic resistance in Salmonella is a growing public health concern.
- Hospital-acquired infections often involve multidrug-resistant pathogens.
- The relationship between plasmid load, virulence, and colonization in Salmonella is not fully understood.
Purpose of the Study:
- To investigate the virulence and colonization potential of antibiotic-resistant Salmonella strains compared to sensitive strains.
- To explore the correlation between plasmid content and observed phenotypic differences.
Main Methods:
- Experimental infection of mice via intraperitoneal and enteral routes using Salmonella strains.
- Plasmid profiling of antibiotic-resistant and sensitive Salmonella strains.
- Assessment of virulence through survival rates and colonization via keratoconjunctival and conjunctival tests.
Main Results:
- Antibiotic-resistant Salmonella strains demonstrated lower virulence in mouse models compared to sensitive strains.
- Multidrug-resistant strains harbored significantly more plasmids (3-10) than sensitive strains (1-2).
- A high percentage (80%) of multidrug-resistant strains showed positive results in ocular tests, indicating strong colonization ability.
Conclusions:
- The reduced virulence of R-plasmid carrying Salmonella in mice may not be linked to the loss of a specific 60 Md plasmid.
- Antibiotic-resistant Salmonella strains retain significant capacity for local colonization, particularly in ocular tissues.
- Findings highlight the complex interplay between antibiotic resistance, plasmid carriage, and Salmonella pathogenicity.