Sulfamethoxazole/trimethoprim (SMX/TMP) effectively combats a wide range of bacterial infections. Its dual mechanism, inhibiting both folic acid synthesis pathways, contributes to this broad spectrum.
Among Gram-positive bacteria, SMX/TMP shows activity against Staphylococcus aureus (including methicillin-sensitive strains, though resistance is increasing), Streptococcus pneumoniae, and Streptococcus pyogenes. However, resistance is a growing concern, and susceptibility testing is crucial before prescribing.
For Gram-negative bacteria, SMX/TMP targets Escherichia coli, Klebsiella pneumoniae, Haemophilus influenzae, and Proteus mirabilis, among others. Again, resistance patterns vary geographically and temporally, demanding regular monitoring of local antibiotic susceptibility.
Specific susceptibility should always be determined through laboratory testing to guide optimal treatment choices. Factors influencing bacterial susceptibility include bacterial species, geographic location, and prior antibiotic exposure. Always refer to current guidelines for appropriate usage.
The combination’s synergistic effect enhances its efficacy. Sulfamethoxazole blocks dihydropteroate synthase, while trimethoprim inhibits dihydrofolate reductase. This sequential blockade disrupts folic acid synthesis, critical for bacterial growth and replication.
