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An R plasmid of Serratia marcescens transferable to Pseudomonas aeruginosa
Abstract:
Hospital isolates of Serratia marcescens able to transfer resistance to up to 11 antibiotics were found to contain conjugative R plasmids. One set of strains harbors only a single R plasmid with a mass of 89 megadaltons (Mdal). This plasmid codes for resistance to nine antibiotics including ampicillin, carbenicillin, cephalothin, streptomycin, kanamycin, gentamicin, tobramycin, sisomycin, and sulfonamides. The 2nd set of strains harbors 2 R plasmids, 1 with a mass of 89 Mdal, the other 57 Mdal. Analysis of progeny from genetic crosses indicates that the larger R plasmid codes for resistance to the same antibiotics as does the 89-Mdal plasmid described above. The 57-Mdal species codes for resistance to ampicillin, carbenicillin, cephalothin, kanamycin, neomycin, and tetracycline. The 89- and 57-Mdal R plasmids appear unrelated by a number of genetic and physical criteria. The 89-Mdal plasmid, but not the 57-Mdal species, is transferable by conjugation to Pseudomonas aeruginosa, and renders this species stably resistant to carbenicillin, streptomycin, kanamycin, gentamicin, tobramycin, and sisomycin.
Insights
Hospital bacteria, Serratia marcescens, carry R plasmids conferring antibiotic resistance. Researchers identified two types of R plasmids, one 89 Mdal and another 57 Mdal, with varying resistance profiles and transfer capabilities.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Hospital-acquired infections pose a significant threat.
- Antibiotic resistance in bacteria is a growing global health concern.
- Serratia marcescens is an opportunistic pathogen frequently found in hospital environments.
Purpose of the Study:
- To characterize the R plasmids responsible for antibiotic resistance in Serratia marcescens.
- To determine the genetic and physical properties of these R plasmids.
- To investigate the transferability of R plasmids between bacterial species.
Main Methods:
- Isolation and characterization of R plasmids from Serratia marcescens.
- Determination of plasmid size using molecular weight markers.
- Conjugation experiments to assess plasmid transferability.
- Genetic and physical analysis of plasmid DNA.
Main Results:
- Two sets of Serratia marcescens strains were identified, harboring either a single 89 Mdal R plasmid or two R plasmids (89 Mdal and 57 Mdal).
- The 89 Mdal plasmid confers resistance to nine antibiotics, while the 57 Mdal plasmid confers resistance to six antibiotics.
- The 89 Mdal plasmid is transferable to Pseudomonas aeruginosa, conferring stable resistance to multiple antibiotics, whereas the 57 Mdal plasmid is not transferable.
- Genetic and physical analyses indicate that the 89 Mdal and 57 Mdal plasmids are unrelated.
Conclusions:
- Conjugative R plasmids are responsible for extensive antibiotic resistance in hospital isolates of Serratia marcescens.
- The 89 Mdal R plasmid plays a significant role in the spread of antibiotic resistance within and between bacterial species.
- Understanding the characteristics of these R plasmids is crucial for developing strategies to combat antibiotic resistance.