Antibiotics Flashcards
What is the structure of Gram (+) bacteria?
Thick peptidoglycan layer, contains teichoic acid, no outer membrane, stains purple.
What is the structure of Gram (-) bacteria?
Thin peptidoglycan layer, outer membrane with lipopolysaccharides (LPS), contains porins, stains pink.
What are the five general properties of antimicrobial agents?
Solubility in body fluids, selective toxicity, stability and resistance to degradation, spectrum of activity, limited side effects.
Name three Gram (+) bacteria and the diseases they cause.
Staphylococcus aureus: skin infections.
Streptococcus pyogenes: strep throat.
Clostridium difficile: pseudomembranous colitis.
Name three Gram (-) bacteria and the diseases they cause.
Escherichia coli: UTIs.
Pseudomonas aeruginosa: hospital-acquired infections.
Neisseria gonorrhoeae: gonorrhea.
Name three atypical bacteria and the diseases they cause.
Mycoplasma pneumoniae: atypical pneumonia.
Chlamydia trachomatis: STIs.
Rickettsia spp.: Rocky Mountain spotted fever.
What is the spectrum of activity of antibiotics?
The range of pathogens an antibiotic can target (narrow vs. broad-spectrum).
What is selective toxicity in antibiotics?
The ability to target bacterial processes without harming host cells.
What are the five main targets of antimicrobial agents?
Cell wall synthesis: penicillins, cephalosporins.
Cell membrane: polymyxins.
Protein synthesis: tetracyclines, macrolides.
Nucleic acid synthesis: fluoroquinolones.
Folic acid synthesis: sulfonamides, trimethoprim.
How do beta-lactam antibiotics kill bacteria?
Inhibit transpeptidase enzymes, preventing peptidoglycan cross-linking, leading to bacterial lysis.
What are three mechanisms of beta-lactam resistance?
Beta-lactamases hydrolyze the beta-lactam ring.
Altered penicillin-binding proteins (PBPs).
Decreased permeability via porin mutations in Gram (-) bacteria.
What are examples of penicillins and their uses?
Penicillin G: narrow-spectrum, Gram (+), used for strep, C-diff, meningitis.
What are examples of cephalosporins and their uses?
Cephalexin: first-generation, Gram (+), used for skin infections and UTIs.
What are examples of carbapenems and their uses?
Imipenem: broad-spectrum, used for serious hospital-acquired infections, sepsis, and pneumonia.
What are examples of monobactams and their uses?
Aztreonam: Gram (-), used for UTIs, lower respiratory tract infections, and Gram (-) sepsis.
What are the major adverse effects of penicillins?
Allergic reactions, GI upset, interstitial nephritis.
What are the major adverse effects of cephalosporins?
Hypersensitivity, bleeding disorders, superinfections.
What is a key feature of imipenem, and how is it used?
Broad-spectrum, co-administered with cilastatin to prevent renal degradation.
What is a benefit of meropenem over imipenem?
Similar broad-spectrum activity but less nephrotoxic.
Why is premature termination of antibiotics problematic?
Encourages resistance, leading to infection relapse or persistence.
What are the clinical uses of vancomycin?
Treats MRSA and penicillin-resistant Gram (+) infections.
What are the toxicities of vancomycin?
Red man syndrome, nephrotoxicity, ototoxicity.
How do polymyxins work, and what bacteria do they target?
Bind bacterial membrane phospholipids, disrupting integrity, targeting Gram (-) bacteria.
Why are protein synthesis inhibitors broad-spectrum?
They target bacterial ribosomes (70S), which differ from human ribosomes (80S).
What are the toxicities of tetracyclines?
DEVILS CAP: Dentition issues, epigastric pain, severe nausea/vomiting/diarrhea, vestibular toxicity, liver damage, kidney damage, superinfection, phototoxicity.
What are examples of tetracyclines?
Doxycycline, tetracycline.
What are examples of macrolides?
Azithromycin, erythromycin.
What are examples of other protein synthesis inhibitors?
Clindamycin, linezolid.
How do sulfonamides affect bacterial folic acid synthesis?
Inhibit dihydropteroate synthase.
How does trimethoprim affect bacterial folic acid synthesis?
Inhibits dihydrofolate reductase.
What are the clinical uses of sulfonamides and trimethoprim?
UTIs, pneumocystis pneumonia, toxoplasmosis.
How do fluoroquinolones inhibit bacterial nucleic acid synthesis?
Inhibit DNA gyrase and topoisomerase IV, preventing DNA replication and transcription.
What are problems caused by disruption of normal microflora?
Superinfections (e.g., C-diff colitis), yeast infections, reduced pathogen competition.
What questions should guide antibiotic selection?
Clinical diagnosis, causative organism, antimicrobial susceptibility, spectrum, patient-specific factors.
