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Distribution of insertion sequence IS1 in multiple-antibiotic resistant clinical Enterobacteriaceae strains
J Ramirez-Santos1, G Alvarez, E Cisneros
1Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, UNAM, Mexico City.
Abstract:
The presence of insertion sequence IS1 in 70 multiple-antibiotic resistant clinical strains was determined. This 70-strain collection comprised 46 Escherichia coli, 18 Salmonella and 6 Shigella strains. The presence of IS1 was detected in the chromosome and plasmids of 73% and 63% of the strains, respectively, and 51% of the strains carried IS1 in both. The frequency of IS1 was higher in Salmonella than in E. coli and Shigella strains. A total of 31 strains carried large plasmids with IS1; 10 of these strains (32.3%) were able to transfer all or some of the antibiotic resistance markers to E. coli K12 or S. typhimurium recipient strains. Resistance markers of all clinical strains were maintained stably after several generations of growth. The presence of IS1 in a relatively high percentage of plasmids of multiple-antibiotic resistant clinical isolates, suggests a role for this sequence in the dissemination of genes which code for antibiotic resistance.
Insights
Insertion sequence IS1 is prevalent in antibiotic-resistant bacteria like E. coli, Salmonella, and Shigella. Its presence on plasmids suggests IS1 may help spread antibiotic resistance genes among clinical strains.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Multiple-antibiotic resistance (MAR) is a growing public health concern.
- Insertion sequences (IS) are mobile genetic elements that can influence bacterial genome structure and gene expression.
- IS1 is a well-characterized insertion sequence found in various bacterial species.
Purpose of the Study:
- To determine the prevalence of insertion sequence IS1 in clinical isolates of multiple-antibiotic resistant bacteria.
- To investigate the association between IS1 presence and antibiotic resistance gene dissemination.
Main Methods:
- Analysis of 70 clinical bacterial strains (46 Escherichia coli, 18 Salmonella, 6 Shigella) for the presence of IS1.
- Detection of IS1 in both chromosomal and plasmid DNA.
- Conjugation experiments to assess the transfer of antibiotic resistance markers.
Main Results:
- IS1 was detected in 73% of strains on the chromosome and 63% on plasmids; 51% carried IS1 in both locations.
- IS1 frequency was higher in Salmonella compared to E. coli and Shigella.
- Ten strains with IS1-carrying plasmids (32.3%) transferred antibiotic resistance markers to recipient strains.
- Antibiotic resistance markers remained stable through multiple generations.
Conclusions:
- IS1 is frequently found in multiple-antibiotic resistant clinical isolates, particularly on plasmids.
- The presence of IS1 on transferable plasmids suggests its role in the dissemination of antibiotic resistance genes.
- Further research is warranted to fully elucidate the mechanisms by which IS1 contributes to antibiotic resistance spread.