Characterization of mutations contributing to sulfathiazole resistance in Escherichia coli

Area of Science:

• Microbiology
• Genetics
• Molecular Biology

Background:

• Sulfathiazole is an antibiotic targeting dihydropteroate synthase (DHPS).
• Antibiotic resistance mechanisms are crucial for understanding microbial evolution and treatment efficacy.
• Escherichia coli is a model organism for studying bacterial genetics and resistance.

Purpose of the Study:

• To identify genetic mutations conferring sulfathiazole resistance in Escherichia coli.
• To characterize the molecular basis of resistance in laboratory-selected strains.
• To investigate the contribution of specific genes and mutations to sulfathiazole resistance.

Main Methods:

• P1 transduction was used to map resistance genes.
• Nucleotide sequence analysis identified specific mutations.
• Allelic replacement experiments were performed to assess gene function.
• Characterization of secondary resistance determinants was conducted.

Main Results:

• A mutation in the folP gene, identical in two resistant E. coli strains, was identified.
• This folP mutation resulted in a Pro64Ser substitution in DHPS.
• The folP mutation alone conferred only low-level sulfathiazole resistance.
• An amplified secondary resistance determinant, identified as bcr (bicyclomycin resistance), was found.
• An additional mutation, sux, was identified and affects purine metabolism.

Conclusions:

• Sulfathiazole resistance in these E. coli strains is multifactorial, involving mutations in folP and other genetic elements.
• The resistant DHPS (encoded by folP) is necessary but not sufficient for high-level resistance.
• The bcr gene and the sux mutation contribute significantly to the overall resistance phenotype.
• Understanding these complex resistance mechanisms is vital for combating antibiotic resistance.