Screening and molecular characterization of plasmid-mediated fosfomycin resistance in Enterobacterales

Area of Science:

• * Clinical microbiology and infectious diseases.
• * Antimicrobial resistance mechanisms and surveillance.

Background:

• * Fosfomycin is an important antibiotic for treating various infections, including urinary tract infections (UTIs).
• * Increasing resistance among Enterobacterales, particularly Escherichia coli, threatens fosfomycin's clinical utility.
• * A study was conducted in a new hospital with no prior fosfomycin use to assess resistance in Enterobacterales isolates.

Purpose of the Study:

• * To investigate the prevalence and genetic basis of fosfomycin resistance in Enterobacterales.
• * To identify potential mechanisms of resistance, including plasmid-mediated and chromosomal genes.
• * To inform infection control strategies in healthcare settings.

Main Methods:

• * Analysis of 397 non-duplicate Enterobacterales isolates (E. coli, K. pneumoniae, etc.).
• * Antimicrobial susceptibility testing and PCR screening for fosfomycin resistance genes (fosA3, fosA4).
• * Sodium phosphonoformate (PPF) test, mating-out, and transformation assays to assess resistance transferability.

Main Results:

• * Only four E. coli isolates exhibited plasmid-mediated fosfomycin resistance determinants (fosA3 and fosA4).
• * Transferability assays indicated that most fosfomycin resistance in Enterobacterales was chromosomally encoded.
• * No additional transferable fosfomycin resistance was detected.

Conclusions:

• * Early detection of fosfomycin resistance carriers is crucial in new hospital settings.
• * Screening can prevent the spread of plasmid-mediated resistance, particularly via IncF-type plasmids.
• * Routine surveillance of fosfomycin resistance supports infection control and preserves antibiotic effectiveness.