Intro to Antimicrobials Flashcards
What are antimicrobials?
Drugs that destroy microbes, prevent their multiplication or growth, or prevent their pathogen action
What are the 5 classes of antibiotics (by mechanism)?
Inhibit cell wall synthesis
Inhibit protein synthesis
Alter nucelic acid metabolism
Inhibit folate metabolism
Other
Examples of antibiotics that inhibit cell wall synthesis and inhibit protein synthesis
Examples of antibiotic classes that alter nucelic acid metabolism, inhibit folate metabolism, and misc
Why are beta lactams a target for antibiotics?
Beta lactams link the peptidoglycan layer of cell wall
Antibiotics target the transpeptidases that catalyze this reaction
Examles: Penicillins, cephalosporins, monobactams, carbapenams
Beta lactamase is an enzyme that lyses these antibiotics and confers resistance
Treats syphilis, treats Group A Streptococcus
Gonorrhea is resistant to penicillin
What is vancomycin used for?
Inhibits peptidoglycan synthesis which makes cell wall/peptidoglycan which is required for cell wall by binding D-Ala-D-Ala terminals
Prevents cross-linking of the peptidoglycan chains
Only active against gram positive bacteria
Used for infection caused by methicillin resistant Staphylococci (MRSA)
What are examples of protein synthesis inhibitors?
** they are usually bacteriostatic; don’t actually kill the bacteria
Aminoglycosides: block initiation of translation; treat pseudomonas
Tetracyclines: block attachment of tRNA to ribosome; treat acne, lyme disease
Streptogramins: each interferes with unique step in protein synthesis
Macrolidse: prevents continuation of protein synthesis; azithromycin (Z pack) can treat outpatient pneumonia
Chloramphenicol: prevent peptide bond formation
Lincosamides: prevents continuation of protein synthesis; clindamycin treat oral abscess (gram positive & anaerobic coverage)
Oxazolidinodes: interfere with initiation of protein synthesis; linzeloid treats MRSA
30S ribosome is where its AT: aminoglycosides and tetracyclines act on it; you’d rather be 30 not 50 – all other protein synthesis inhibitors act at 50S ribosome
What are polymyxins? What makes it dangerous?
Binds LPS in outer membrane of gram neg bacteria & destroys bacterial cell membrane with a detergent like mechanism
Also act as detergent on kidney cell membranes –> hepatotoxicity *and neurotoxicity
How do you determine the MIC for an antibiotic?
Broth dilution: try growing bacteria in diff conc of antibiotic; when it stops growing, that’s the MIC
Disk diffusion: grow colonies around bacteria; clear ring on plate around antiB indicates that bacteria can’t grow– bacteria is resistant to antibiotic if there is no ring around it.
E test: has gradient of antibiotic on a plate –> where the bacteria doesn’t grow = MIC
