MICROBIOLOGY - Antimicrobials Flashcards
Which antibiotics inhibit bacterial cell wall synthesis? (3)
Penicillins, cephalosporins (ceftriaxone), vancomycin
What is the mechanism of action of fluoroquinolones?
BACTERICIDAL
Gram +ve: Inhibit topoisomerase IV
Gram -ve (more potent):
Inhibit DNA replication by action on bacterial DNA gyrase
Systemically, what can chloramphenicol cause?
Aplastic anaemia
Which antibiotics inhibit protein synthesis? (5)
Which antibiotics inhibit 30S subunit
Which antibiotics inhibit 50S subunit
30S: tetracycline, aminoglycosides (messenger RNA)
50S: Macrolides, Lincosamides, Chloramphenicol
What antibiotics inhibit cell wall synthesis?
Beta lactam antibiotics - penicillin, cephalosporins, vancomycin
What antibiotics inhibit folic acid synthesis?
Sulphonamides
Trimethoprim
What antibiotics inhibit DNA gyrase and transcription?
Fluoroquinolones
Which antibiotic is the most retino-toxic when given intravitreally?
Gentamicin (gram negative cover)
What are aminoglycosides not effective against?
Streptococcus and strict anaerobes
what is the mechanism of action of azole antifungals (fluconazole, itraconazole, ketoconazole)?
inhibit cell membrane synthesis - they inhibit the synthesis of sterols by inhibiting P450 dependent enzymes (C14-demethylase) which are an important constituent in fungal cell membranes (anti-mycotics)
What ocular side effect occurs with prolonged use of ciprofloxacin?
Corneal crystalline precipitates
What type of bacteria do tetracyclines target? (3)
Gram +ve
Gram -ve
Chlamydia
Which drug can be used for infections caused by aspergillus and candida?
Topical amphotericin
Which antibiotics are known to be associated with IIH?
- Tetracyclines
- Fluoroquinolones
Which antibiotics are bacteriocidal? (4)
- Aminoglycosides
- B-Lactam
- Vancomycin
- Fluoroquinolones
Which antibiotics are bacteriostatic? (4)
- Chloramphenicol
- Macrolides
- Tetracycline
- Sulphonamides
What is the mechanism of action of chloramphenicol?
BACTERIOSTATIC
50S subunit:
inhibits peptidyl-transferase and prevents peptide bond formation of to amino acids
What is the mechanism of action of macrolides?
BACTERIOSTATIC
50S Subunit: interfering with translocation
Broad spectrum: Gram + ve > atypical (mycoplasma/ chlamydia) > Gram -ve.
What is the mechanism of action of tetracyclines?
TETRA blocks tRNA on Thirty Subunit
BACTERIOSTATIC
inhibition of aminoacyltransferase tRNA to 30S subunit preventing binding to A-site.
What is the mechanism of action of sulphonamides?
BACTERIOSTATIC
inhibits dihydropteroate synthase –> converts para-aminobenzoic acid to folate
What is the mechanism of action of aminoglycosides?
BACTERICIDAL: GRAM -VE.
30S Subunit:
Prevents binding of mRNA to ribosome leading to mRNA misreading and premature termination of protein synthesis
What is the mechanism of action of Beta Lactams?
BACTERICIDAL
Inhibits crosslinks of peptidoglycan strands causing cell lysis
What is the mechanism of action of vancomycin
BACTERICIDAL
Binds to pentapeptide chains and prevents peptidoglycan assembly
Targets Gram +ve.
What is the mechanism of action of fluoroquinolone?
Inhibits bacterial DNA gyrase
What is the mechanism of action of metronidazole?
Disrupts DNA synthesis targets anaerobes
What are aminoglycosides effective against?
What are they not effective against?
- aerobic gram negative bacili
- proteus
- staphylococcus
non effective against:
1. streptococcus
2. anaerobes
What is the most common side effect of gentamicin?
oscilopsia then cochlear injury then renal toxicity
What antimicrobials affect cell wall synthesis? (3)
penicillins
cephalosporins
vancomycin
What antimicrobials affect protein synthesis? (4)
tetracycline
gentamicin
erythromycin
chloramphenicol
Which antibiotic has the best ocular penetration when given orally?
ciprofloxacin (fluoroquinolones)
What are the second generation fluoroquinolones? (2)
What are the third generation fluoroquinolones? (1)
What are the fourth generation fluoroquinolones? (1)
Second gen - cipro, ofloxacin,
Third gen - levofloxacin,
Fourth gen - Moxifloxacin
Mechanism of action diagram of anti-microbials
What are the
1st generation cephalosporins
2nd generation cephalosporins
3rd generation cephalosporins
4th generation cephalosporins
1 - FA/PHA - cefazolin
2 - Cefuroxime
3 - ONE/IME - ceftriaxone, ceftazidine
4 - PI - Cefepime
What are cephalosporins active against which generation?
1st - gram positive (staph/strep)
2nd - gram +ve + some gram -ve (haemophilus, neisseria)
3rd - gram +ve + gram -ve bacilli and pseudomonas
What bacteria are cephalosporins NOT effective against (3)
Listeria, Legionella, MRSA
What is the mechanism of action of antimicrobials?
What is the mechanism of action of micafungin?
Interferers with glucan synthesis, which is an essential component of fungal cell walls.
What is the mechanism of action of polyene antifungal drugs (amphotericin, nystatin)
Interact with sterols in cell membrane to form channels through which small molecules leak from inside of fungal cell to the outside.
What is the mechanism of action of foscarnet?
pyrophosphate analogue which Reversibly inhibits viral-specific DNA polymerase and reverse transcriptase
Which antimicrobial agents are used in the treatment of acanthomoeba keratitis? (4)
Aminoglycosides (neomycin)
Diamidines (Brolene)
Imidazole (ketoconazole)
Antiseptic biocides (polyhexamethylene biguanide)
