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Abstract:
60 fosfomycin-resistant strains of gram-negative bacilli are submitted to conjugation experiments using as recipient cell E. coli K12 which is nalidixic acid resistant. After mating, the number of fosfomycin-resistant E. coli K2 colonies growing on selection plates containing nalidixic acid and fosfomycin never surpassed the normal rate of mutation for fosfomycin-resistance of the recipient strain. In 65% of the experiments, plasmidic resistance to other antimicrobials was transferred to E. coli K12, but was never accompanied by demonstrable fosfomycin resistance. High rate of normal mutation of recipient strain is signaled as the main problem for detecting the plasmidic nature of fosfomycin resistance. With our criteria regarding this fact we have been unable to confirm the plasmidic nature of fosfomycin resistance.
Insights
Researchers investigated fosfomycin resistance in gram-negative bacilli. Conjugation experiments could not confirm plasmid-mediated fosfomycin resistance due to high mutation rates in the recipient strain.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Fosfomycin is a crucial antibiotic for treating Gram-negative bacterial infections.
- The emergence of antibiotic resistance, including to fosfomycin, poses a significant public health threat.
- Understanding the mechanisms of fosfomycin resistance, particularly plasmid-mediated transfer, is essential for effective treatment strategies.
Purpose of the Study:
- To investigate the potential for plasmid-mediated transfer of fosfomycin resistance among Gram-negative bacilli.
- To determine if fosfomycin resistance can be co-transferred with other antimicrobial resistances via plasmids.
- To identify challenges in detecting plasmidic fosfomycin resistance.
Main Methods:
- Conjugation experiments were performed using 60 fosfomycin-resistant Gram-negative bacilli strains.
- Escherichia coli K12 (nalidixic acid resistant) served as the recipient strain.
- Selection of transconjugants was done on plates containing nalidixic acid and fosfomycin.
Main Results:
- The number of fosfomycin-resistant transconjugant colonies did not exceed the spontaneous mutation rate of the recipient strain.
- Plasmid-mediated transfer of resistance to other antimicrobials occurred in 65% of experiments.
- Fosfomycin resistance was not co-transferred with other plasmid-mediated resistances.
Conclusions:
- The high spontaneous mutation rate for fosfomycin resistance in the recipient strain complicates the detection of plasmid-mediated transfer.
- Under the tested conditions, the plasmidic nature of fosfomycin resistance could not be confirmed.
- Further studies with modified methodologies may be needed to elucidate the mechanisms of fosfomycin resistance transfer.