Abstract
Trimethoprim and sulfamethoxazole are used commonly together as cotrimoxazole for the treatment of urinary tract and other infections. The evolution of resistance to these and other antibacterials threatens therapeutic options for clinicians. We generated and analysed a chemical-biology-whole-genome data set to predict new targets for antibacterial combinations with trimethoprim and sulfamethoxazole. For this we used a large transposon mutant library in Escherichia coli BW25113 where an outward-transcribing inducible promoter was engineered into one end of the transposon. This approach allows regulated expression of adjacent genes in addition to gene inactivation at transposon insertion sites, a methodology that has been called TraDIS-Xpress. These chemical genomic data sets identified mechanisms for both reduced and increased susceptibility to trimethoprim and sulfamethoxazole. The data identified that over-expression of FolA reduced trimethoprim susceptibility, a known mechanism for reduced susceptibility. In addition, transposon insertions into the genes tdk, deoR, ybbC, hha, ldcA, wbbK and waaS increased susceptibility to trimethoprim and likewise for rsmH, fadR, ddlB, nlpI and prc with sulfamethoxazole, while insertions in ispD, uspC, minC, minD, yebK, truD and umpG increased susceptibility to both these antibiotics. Two of these genes’ products, Tdk and IspD, are inhibited by AZT and fosmidomycin respectively, antibiotics that are known to synergise with trimethoprim. Thus, the data identified two known targets and several new target candidates for the development of co-drugs that synergise with trimethoprim, sulfamethoxazole or cotrimoxazole. We demonstrate that the TraDIS-Xpress technology can be used to generate information-rich chemical-genomic data sets that can be used for antibacterial development.
Highlights
The pyrimidine antibiotic trimethoprim is used widely to treat urinary and respiratory tract infections
In E. coli and other susceptible bacteria, trimethoprim is an inhibitor of the folA gene product, dihydrofolate reductase (DHFR), inhibiting the conversion of dihydrofolate to tetrahydrofolate, a methyl donor required for the biosynthesis of thymidylate, pyrimidines, purines and methionine
One step in the biosynthesis of tetrahydrofolate includes the formation of dihydropteroate (DHP) from pteridine diphosphate and para-aminobenzoic acid, in a reaction catalysed in E. coli by the folP gene product, dihydropteroate synthase (DHPS)
Summary
The pyrimidine antibiotic trimethoprim is used widely to treat urinary and respiratory tract infections. The antibiotic sulfamethoxazole is a pABA analogue that acts by being incorporated into this reaction instead of pABA, converting pteridine diphosphate into the dead-end, non-metabolite, dihydropterin-sulfamethoxazole. This starves the cell of dihydropteroate and, tetrahydrofolate [3]. Sulfamethoxazole is rarely used alone as an antibiotic due to bacterial resistance and availability of more active and less toxic alternatives Due to it inhibiting folate synthesis, it is used in combination with trimethoprim as co-trimoxazole, to treat urinary and respiratory tract infections, otitis media, nocardiosis, pneumonia caused by Pneumocystis jirovecii, and toxoplasmosis
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
