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Transposable multiple antibiotic resistance in Streptococcus pneumoniae
Abstract:
A mobile genetic element, designated Tn1545, was detected in the chromosome of Streptococcus pneumoniae BM4200, a clinical isolate multiply resistant to antibiotics. The 25.3 kb element conferred resistance to kanamycin and structurally related aminoglycosides by synthesis of a 3'-aminoglycoside phosphotransferase type III (aphA-3), to macrolide-lincosamide-streptogramin B-type antibiotics (ermAM), and to tetracycline (tetM). Tn1545 was self-transferable to a recombination deficient S. faecalis strain where it was able to transpose to various sites, induce insertional mutations and was apparently cleanly excised. The element also conjugated to and transposed to the chromosome of S. faecalis, S. lactis, S. diacetylactis, S. cremoris, S. sanguis, Staphylococcus aureus, and Listeria monocytogenes. The properties of the conjugative transposon Tn1545 could account for the sudden emergence, rapid dissemination, and stabilisation of multiple resistance to antibiotics in S. pneumoniae in the absence of plasmids.
Insights
A novel mobile genetic element, Tn1545, was discovered in antibiotic-resistant Streptococcus pneumoniae. This conjugative transposon confers resistance to multiple antibiotics and can transfer between bacterial species, aiding rapid spread.
Area of Science:
- Molecular Biology
- Microbiology
- Genetics
Background:
- Antibiotic resistance is a growing global health threat.
- Mobile genetic elements play a crucial role in the dissemination of antibiotic resistance genes.
- Streptococcus pneumoniae is a significant human pathogen often exhibiting multidrug resistance.
Purpose of the Study:
- To characterize a novel mobile genetic element, Tn1545, found in a multidrug-resistant Streptococcus pneumoniae isolate.
- To investigate the genetic basis of antibiotic resistance conferred by Tn1545.
- To determine the transferability and transposition capabilities of Tn1545 in various bacterial hosts.
Main Methods:
- Isolation and characterization of the mobile genetic element Tn1545 from Streptococcus pneumoniae BM4200.
- Molecular analysis to identify resistance genes (aphA-3, ermAM, tetM) within Tn1545.
- Conjugation experiments using a recombination-deficient Enterococcus faecalis strain to assess Tn1545 transferability and transposition.
Main Results:
- Tn1545 is a 25.3 kb mobile genetic element conferring resistance to kanamycin (aphA-3), macrolides (ermAM), and tetracycline (tetM).
- Tn1545 demonstrated self-transferability and transposition to various genomic sites in a recombination-deficient Enterococcus faecalis strain.
- The element successfully conjugated and transposed into the chromosomes of multiple Gram-positive bacteria, including Streptococcus species, Staphylococcus aureus, and Listeria monocytogenes.
Conclusions:
- Tn1545 is a conjugative transposon capable of mediating the spread of multidrug resistance among diverse bacterial species.
- The properties of Tn1545 provide a potential mechanism for the rapid emergence and dissemination of antibiotic resistance in Streptococcus pneumoniae, independent of plasmids.
- Understanding the dynamics of mobile genetic elements like Tn1545 is critical for combating the spread of antibiotic resistance.