Acquired resistance to trimethoprim-sulfamethoxazole during Whipple disease and expression of the causative target gene.
BACKGROUND
Whipple disease is a chronic infection caused by Tropheryma whipplei. Trimethoprim-sulfamethoxazole is recommended for treatment of Whipple disease but is associated with treatment failure. T. whipplei is resistant in vitro to trimethoprim, because the gene targeted by this agent is missing.


METHODS
A patient experienced clinical failure during treatment with trimethoprim-sulfamethoxazole. The gene encoding the enzyme putatively believed to be dihydropteroate synthase (DHPS), the target of sulfamethoxazole, was amplified and sequenced for 20 T. whipplei strains from our laboratory and for isolates recovered from a case patient at the time of diagnosis and the time of treatment failure. An Escherichia coli knockout strain for this gene was complemented with the sequences from a susceptible strain and from isolates recovered from the case patient. Susceptibilities of complemented E. coli to sulfamethoxazole were tested.


RESULTS
The target gene was identified among genes encoding a unique trifunctional enzyme in which DHPS is combined with the 2 preceding enzymes of the folate biosynthesis pathway. Changes in the amino acid sequence of putative DHPS were detected in the case patient. Gene complementation showed that the gene encoding putative DHPS restored the folate biosynthesis pathway and susceptibility to sulfamethoxazole, whereas the mutated sequence was associated with sulfamethoxazole resistance.


CONCLUSIONS
Antibiotic susceptibility of fastidious bacteria such as T. whipplei can be evaluated by means of gene complementation techniques. Mutations in the target gene of sulfamethoxazole appear during treatment.
Bakkali
Nawal
N
Unité des Rickettsies, IFR 48, Centre National de la Recherche Scientifique UMR 6020, Marseille, France.
Fenollar
Florence
F
Biswas
Silpak
S
Rolain
Jean-Marc
JM
Raoult
Didier
D
D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001665:Binding Sites; D004094:Dihydropteroate Synthase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D005838:Genotype; D006801:Humans; D008297:Male; D008958:Models, Molecular; D009154:Mutation; D011487:Protein Conformation; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000494:pharmacology* / Q000627:therapeutic use; D054851:Tropheryma / Q000187:drug effects* / Q000235:genetics; D008061:Whipple Disease / Q000188:drug therapy* / Q000382:microbiology
D000900:Anti-Bacterial Agents; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D004094:Dihydropteroate Synthase