Sulphonamide resistance gene sul3 found in Escherichia coli isolates from human sources.
OBJECTIVE
The aim of this study was to investigate the molecular basis of an observed increasing resistance to trimethoprim and sulphonamides despite a simultaneous decline in co-trimoxazole consumption. The distribution of sulphonamide resistance genes sul1, sul2 and the recently discovered sul3 was studied in a collection of clinical isolates of Enterobacteriaceae.


METHODS
PCR with primers specific for sul1, sul2 and sul3 was used to detect the three known sulphonamide resistance genes in the isolate collection. Sequence analysis was used for confirmation of results. Restriction endonuclease digestion and conjugational transfer assays were used for plasmid analysis.


RESULTS
In 64 sulphonamide-resistant isolates, 39 sul1 genes and 48 sul2 genes were detected. Twenty-five isolates carried both sul1 and sul2 and two were negative for both genes. With PCR and sequence analysis these two were shown to harbour the new sulphonamide resistance gene sul3, which was carried by different plasmids.


CONCLUSIONS
Sulphonamide resistance gene sul3, which is widespread among pigs in Switzerland, has now also been identified in two different clinical isolates of Escherichia coli, located in urinary tract infections in patients in Sweden.
Department of Microbiology and Tumor Biology-MTC, Clinical Microbiology, Karolinska Institute, Karolinska Hospital L2:02, Stockholm, SE-171 76, Sweden. malin.grape@ks.se
Malin
M
Grape
Lars
L
Sundström
Göran
G
Kronvall
D000890:Anti-Infective Agents / Q000494:pharmacology*; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000235:genetics; D004094:Dihydropteroate Synthase / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics*; D004927:Escherichia coli Infections / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000494:pharmacology*; D006801:Humans; D010957:Plasmids / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013449:Sulfonamides / Q000494:pharmacology*; D014296:Trimethoprim Resistance / Q000235:genetics; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000494:pharmacology; D014552:Urinary Tract Infections / Q000382:microbiology*
D000890:Anti-Infective Agents; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D013449:Sulfonamides; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D004094:Dihydropteroate Synthase; C487459:Sul3 protein, E coli