Chapter 93- Sulfonamides and Trimethoprim Flashcards
What are sulfonamides?
The first drugs available for the systemic treatment of bacterial infections
When were sulfonamides introduced?
In the 1930s
What impact did sulfonamides have on morbidity and mortality?
Produced a sharp decline in morbidity and mortality from susceptible infections
How has the use of sulfonamides changed over time?
Greatly declined with the advent of penicillin and newer antimicrobial drugs
What is a primary current use of sulfonamides?
Against urinary tract infections (UTIs)
What expanded the indications for sulfonamides in the 1970s?
The introduction of TMP/SMX
What is a key similarity among sulfonamides?
More striking similarities than differences
What is the mechanism of action of sulfonamides?
Structural analogs of para-aminobenzoic acid (PABA)
How do sulfonamides suppress bacterial growth?
By inhibiting the synthesis of tetrahydrofolate
Why is folate important for cells?
Required to make DNA, RNA, and proteins
What reaction do sulfonamides block?
The combination of PABA with pteridine to form dihydropteroic acid
What type of inhibitors are sulfonamides?
Competitive inhibitors
Fill in the blank: Sulfonamides are structural analogs of _______.
para-aminobenzoic acid (PABA)
Why don’t sulfonamides harm mammalian cells?
Mammalian cells take up folate from the diet rather than synthesizing it
Bacteria must synthesize folate as they cannot absorb it from their environment, making them susceptible to sulfonamides.
What is the antimicrobial spectrum of sulfonamides?
Active against a broad spectrum of microbes, including:
* Gram-positive cocci (e.g., MRSA)
* Gram-negative bacilli
* Listeria monocytogenes
* Actinomycetes (e.g., Nocardia)
* Chlamydiae (e.g., Chlamydia trachomatis)
* Some protozoa (e.g., Toxoplasma species, plasmodia, Isospora belli)
* Two fungi (Pneumocystis jiroveci and Paracoccidioides brasiliensis)
Sulfonamides are usually bacteriostatic, requiring adequate host defenses for infection elimination.
What are the principal resistance mechanisms of bacteria to sulfonamides?
- Reduced sulfonamide uptake
- Synthesis of PABA in amounts sufficient to overcome inhibition
- Alteration in the structure of dihydropteroate synthetase
Resistance can be acquired through spontaneous mutation or plasmid transfer (R factors).
True or False: Sulfonamides are bactericidal.
False
Sulfonamides are usually bacteriostatic.
Fill in the blank: Bacteria must synthesize _____ as they cannot absorb it from their environment.
folate
List some of the protozoa that sulfonamides are effective against.
- Toxoplasma species
- Plasmodia
- Isospora belli
Which bacterial species have developed high resistance to sulfonamides?
- Gonococci
- Meningococci
- Streptococci
- Shigellae
