Antibacterial Drugs #2 Flashcards
What drugs Inhibit Nucleic Acid Synthesis
Sulfonamides
Trimethoprim
Rifamprin
Sulfonamide Mechanism
Competitive Inhibitor of Dihydropteroate synthase - which is required for the synthesis of folic acid
Is Sulfonamide Bacteriostatic or bacteriocidal?
Static
Sulfonamide Selectivity
Bacteria must synthesize their own folate, while humans utilize dietary folate
Sulfonamide Antibacterial spectrum
Gram+ and Gram-
Sulfonamide Clinical uses
UTIs
Toxoplasmosis
Malaria
Prophylactive for burns and AIDS patients preventing P jirovecii
Sulfonamide Toxicities
Dose related - Crytalluria, Hemolytic anemia, Kernicterus
Dose Unrelated - Hypersensitivity
Trimethoprim Mechanism
Inhibitor of Dihydrofolate reductase (DHFR)
Is Trimethoprim Bacteriostatic or Bacteriocidal
Static
Trimethoprim Selectivity
Bacteria must synthesize their own folate, while humans utilize dietary folate
Trimethoprim Antibacterial Selectivity
Gram+ and Gram-
Broader spectrum than Sulfonamides
Trimethoprim Clinical Uses
Usually used in combination with Sulfamethoxazole (makes it bacteriocidal)
UTIs
GI infections
P. jarovecii prophylaxis in AIDS patients
Trimethoprim Toxicities
Slight blood dyscrasia
Anemia in patients that are folate deficient
Rifamprin Mechanism
Binds to an inhibits RNA polymerase
Is Rifamprin Bacteriostatic or Bacteriocidal?
Cidal
Rifamprin Selectivity
Does not bind to human RNA
Rifamprin Spectrum
Potent against M. tuberculosis
Some activity against Stphylococci
Rifamprin Clinical Uses
First line anti-tuberculosis in compination with other anto-tubercular drugs (RIPE)
Rifamprin Toxicities
Liver damage - Jaundice
Rifamprin Resistance Mechanisms
Inductance of resistance is rapid - therefor not used as monotherapy
What drugs are DNA damaging?
Quinolones
Nitrofurantoin
Metronidazole
Methenamine
Quinolones mechanism
Poison DNA Gyrase A - inhibiting the uncoiling funciton of DNA gyrase ahead of the replication fork
Are Quinolones bacteriostatic or bacteriocidal?
Cidal
Quinolones Selectivity
Mammalian DNA topoisomerase is not inhibited to the same extent as DNA Gyrase II and Topoisomerase IV in bacteria
Quinolones Spectrum
Gram+ and Gram-
Quinolones Clinical Uses
UTI
RTI
Anti-tubercular
Quinolones Toxicities
Generally well-tolerated
Avoid using with Ciprofloxin with children - leads to potential tendon ruptures
Quinolones Resistance Mechanisms
1) Mutations in Gyrase or Topoisomerase targets
2) Increased efflux pumps
3) Altered porins (gram-)
Nitrofurantoin Mechanism
DNA damage caused by formation of oxygen free radicals subsequent to reduction of a nitro group
Are Nitrofurantoins Bacteriostatic or bacteriocidal?
Static
Nitrofurantoins Selectivity
Bacteria cause reductive activation more extensively than mammalian cells
Nitrofurantoins Antibacterial spectrum
Broad spectrum against Gram+ and Gram-
Not effective against P. aeruginosa
Nitrofurantoins Clinical Uses
UTI
RTI
Anti-tubercular
Nitrofurantoin Toxicities
Poor renal function leads to toxicity - fever, rashes, urticaria, and eventually pulmonary fibrosis
Metronidazole Mechanism
Reductive activation of nitro group specifically in anaerobic bacteria leads to free radical species and reactive intermediates that bind to and effect DNA function
Is Metronidazole bacteriostatic or bacteriocidal?
Cidal
Metronidazole selectivity
Bacteriocidal agent against most obligate anaerobic gram+ bacteria
Metronidazole spectrum
Gram+ anaerobic
Methenamine Mechanism
Hydrolyzed at acidic pH to form formaldehyde - which has been shown to damage DNA
Is Methenamine bacteriostatic or bactericidal?
Cidal
Methenamine antibacterial spectrum
Gram-
Methenamine Clinical Uses
Only for prophylaxis of UTIs
Which drugs Inhibit Cell Wall synthesis?
Beta-Lactams -Penicillins -Cephalosporins -Monobactams -Carbapenems B-lactamase inhibitors Vancomyocin Bacitracin
Penicillin mechanisms
Mimics D-ala-D-ala structure of pentapeptide on peptidoglycan and ties up transpeptidase
Is penicillin bacteriostatic or bactericidal?
Cidal
Penicillin selectivity
Inhibits cell wall synthesis - there is no cell wall in eukaryotic cells
Penicillin clinical uses
Streptococcus pneumoniae
Penicillin resistance mechanisms
1) B-lactmases (Gram+ and gram-)
2) Altere PBPs
3) Altered porins (gram-)
4) Increases efflux (enhanced pump mechanisms)
Are penicillins Time dependent or Concentration dependent?
Time dependent
Cephalosporins Mechanisms
Mimics D-ala-D-ala structure of pentapeptide on peptidoglycan and ties up transpeptidase
Are Cephalosporins bacteriostatic or bacteriocidal?
Cidal
Cephalosporin Selectivity
Inhibits cell wall synthesis - there is no cell wall in eukaryotic cells