Conjugative RP4 Plasmid-Mediated Transfer of Antibiotic Resistance Genes to Commensal and Multidrug-Resistant Enteric...

Area of Science:

• Microbiology
• Genetics
• Molecular Biology

Background:

• Antibiotic resistance genes are frequently located on conjugative plasmids.
• These plasmids can be transferred between bacteria, including commensals and pathogens.
• Understanding plasmid transfer dynamics is crucial for combating antibiotic resistance.

Purpose of the Study:

• To determine the ability of multiple enteric bacteria to acquire and retransfer the broad-host-range RP4 plasmid.
• To investigate plasmid transfer frequencies between different bacterial species.
• To assess plasmid persistence and potential fitness costs in the absence of antibiotic selection.

Main Methods:

• In vitro conjugation experiments using a human commensal Escherichia coli strain carrying the RP4 plasmid.
• Testing transfer to various rifampicin-resistant enteric bacteria, including Vibrio cholerae, Pseudomonas putida, Klebsiella pneumoniae, and Salmonella Typhimurium.
• Quantification of transconjugants via selective media, fluorescence microscopy, and PCR for plasmid confirmation.

Main Results:

• The RP4 plasmid successfully transferred from E. coli to all tested recipients except Pseudomonas aeruginosa.
• Transfer frequencies varied significantly between donor-recipient pairs (10^-2 to 10^-8).
• Secondary retransfer occurred at high frequencies (10^-2 to 10^-7), and plasmid loss was observed over serial passages without antibiotics, indicating a fitness cost.

Conclusions:

• The RP4 plasmid demonstrates broad-host-range transferability to clinically relevant bacterial species.
• Plasmid transfer can occur efficiently without antibiotic selection pressure.
• While a fitness cost exists, the plasmid can persist through multiple bacterial generations.