Microbiology - Antibiotics Flashcards
What is a breakpoint sensitivity testing?
inoculate test strains onto media containing different concentrations of amoxicillin and see whether or not/how many colonies grow.
What is Kirby-bauer disc diffusion method?
Test sensitivity of multiple antibiotic discs against the SAME strain on a plate.
What is rapid chromogenic antibiotic sensitivity testing?
works for B-lactam antibiotics
- substance changes color from YELLOW to RED in the presence of beta lactamase
What is MIC?
Minimum inhibitory concentration assay
- serially diluted antibiotic with constant amount of bacterial inoculum (tubes incubated to determine where growth does not occur)
Examples of antimetabolites antibiotics?
- Sulfonamides (Static, UTI)
- Trimethoprim(Static, UTI)
- Isoniazid (CIDAL, TB)
Examples of antibiotics that inhibits cell wall synthesis?
- Penicillins (B-lactam ring, sensitive to penicillinases + Thiazolidine Ring)
- Cephalosporins (B-lactam ring + Dihydrothiazine Ring) _ similar to penicillin & can be given to ppl who are allergic to penicillin: Cefazolin, Cefuroxime, Ceftriaxone & Ceftazidime = three generations.
- Others (with b-lactam rings but otherwise NOT structurally similar to penicillin):
1. Monobactams: Aztrenam
2. Carbapenems: Imipenem - B-lactamase inhibitors: extend the use of B-lactam by inhibiting the B-lactamase: Clavulanic acid (Augmentin)/Sulbactam
ALL bacteria cell wall synthesis inhibitors are bactericidal. True or False?
TURE!
What are the types of penicillins?
- Early: Penicillin-G (acid labile, needed injection); Penicillin-V/VK (acid stable) _ limited spectrum, mostly against G+ bacteria and G- cocci, ineffective against G- enterics
- Aminopenicillins: Ampicillin; Amoxicillin _ broader spectrum, works on G- enterics
- Extended spectrum penicillins: Tricarcillin; Piperacillin _ active against G- bacillus as well, sacrificed some effectiveness against G+ cocci.
- Anti-staphylococcal penicillins: Oxacillin/Dicloxacillin/Nafcillin/ Methicillin _ resistant to penicillinases
Glycopeptide cell wall synthesis inhibitors?
- Vancomycin (***TOXIC, only used when other antibiotics are ineffective or contraindicated) _ G+ organisms (too BIG to pass through outer membrane)
- Cycloserine (***TOXIC, secondary TB drug)
- Bacitracin (***TOXIC)
What is the antibiotic used to treat MSRA?
Vancomycin! (Only drug available…) VREF (vancomycin-resistant Enterococcus faecalis) is a serious clinical problem…!!! VRSA (Vancomycin resistant S. aureus) hasn’t been discovered…yet…
Antibiotics that affect membrane permeability?
- **CIDAL, though cell growth is NOT required for activity
- Polymyxin B (selective against G- enteric rods, especially important against Pseudomonas)
Antibiotics as inhibitors of protein synthesis?
- Aminoglycosides, targets 30S: Streptmycin//Gentamicin ~requires AEROBIC conditions to be effective
- Tetracyclines (STATIC), binds tRNA to 30S: tetracycline/doxycycline/minocycline
- Inhibitor to 50S (STATIC): Erythromycin/Azithromycin/Chloramphenical/ Clindamycin/Sreptogramins
Antibiotics that inhibits translation by other interactions with the ribosome?
- Oxazolidinones (STATIC): linezplid (Zyvox) designed for against MRSA, VRSA, can be potentially for VREF
Antibiotics that inhibitors translation by other mechanisms (other than interaction with the ribosomes)?
- Mupirocin (binds to specific tRNA synthetase): Low concentration = STATIC, High concentration = CIDAL.
Antibiotics that inhibits DNA replication?
- **CIDAL
- Quinolones: ciprofloxacin and moxifloxacin
- Nitroimidazoles: metronidazole (ANAEROBIC drug)
