sul2

sul2 is a gene encoding a variant of dihydropteroate synthase (DHPS) that provides resistance to sulfonamide antibiotics in bacteria. It is one of several sul genes (sul1, sul2, sul3) found on mobile genetic elements, facilitating horizontal transfer among different bacterial species.

The sul2-encoded DHPS enzyme catalyzes a key step in folate biosynthesis, but sulfonamides mimic para-aminobenzoic acid (PABA) and inhibit this enzyme. The DHPS produced by sul2 has reduced affinity for sulfonamides, allowing folate synthesis to continue in the presence of these drugs. The gene is frequently carried on plasmids, transposons, or integrons, contributing to its rapid spread within bacterial communities.

sul2 has a broad distribution in Gram-negative bacteria, including many Enterobacteriaceae such as Escherichia coli, Klebsiella, and Salmonella, as well as other environmental and clinical isolates. It is also found, though less commonly, in some non-Enterobacteriaceae and occasionally in different ecological niches.

Genetically, sul2 is often located on conjugative plasmids and can be part of larger resistance gene cassettes. It is frequently found alongside other antibiotic resistance determinants, including genes for beta-lactam, tetracycline, and trimethoprim resistance, contributing to multidrug-resistant phenotypes.

Clinically, sul2 contributes to resistance against sulfonamides, which are commonly used in combination therapies such as trimethoprim-sulfamethoxazole. Detection of sul2 is performed by molecular methods like PCR and sequencing, and it is cataloged in resistance gene databases for surveillance and research purposes.

See also: sul1, sul3, antibiotic resistance genes.