Infection / Antibacterials Flashcards
Summarise the categories of antibiotics that act on the bacterial cell wall
please create cool music
- Beta lactams (peniciliins, Carbapenems , Cephalosporins, Monobactam)
- inhibit cell wall synthesase
- cross link peptidyglocan chains
- Beta lactam ring
- penicillin = gram positive cover is good but not gram negative
2) Glycopeptides , only active agaisnt gram positive , stat in anamtonical compartment in which they are administered
- they act in earlier step
- Inhibit incooperateion of building blocks in the cell wall
- vancomycin
2.Summarise the categories of antibiotics that act within the cell (non cell-wall active agents)
- Protein synthesis Inhibitor
- Nucleic acid synthesis inhibitors
- Miscellaneous x 2
3.Illustrate what an antimicrobial resistant organism is with examples of important resistance mechanisms
BTR
the bacteria have 3 main types of defence against antibiotics :
1) Beta lactamases = break down Beta lactams
2) Target site modification ( alters the site where antibiotics act )
3) Restricted access (efflux pumps which remove antibiotics)
Carbapenamases = can break down all BETA LACTAMS !!!!
Classes of antibacterials
6
1) Beta lactams
2) Glycopeptides
3) protein synthesis inhibitors : Macrolides, Aminoglycosides , tetracycline ,
4) Nucleic acid synthesis inhibitors : Quinolones, Metronidazole, Trimethoprim (folate antagonist)
5) Nitrofurantoin
6) Fidaxomicin(RNA polymerase is inhibited )
Beta lactams
Mode of action (2)
classes (4)
β-Lactam antibiotics inhibit bacteria by binding covalently to Penicillin Binding Proteins in the cytoplasmic membrane. This stops formation of the bacteria = they stop cross linking in cell wall so it is very weak
4-5 subtypes :
1) Penicillin and penicilline beta lactamase inhibitor combinations
2) Carbapenems : Meropenems
3) Cephalosporins : cefuroxime (used if they’re allergic to penicillin , DONT have with alcohol )
4) Monobactams : Aztreonam
How do glycopeptides work ( cell wall active antibiotics )
1) prevent formation of peptidyglocan back wall
- vancomycin used in MRSA , C difficile
Protein synthesis inhibitors MAT -mycins -micins -cyclines
1) Macrolides = stop protein synthesis by binding to 50s subunit of ribosome = clarithromycin , erythromycin , azithromycin = used in chest infections , streptococcus pneumoniae , Haemophilus influenzae
2) Aminoglycosides = Bind to 30s ribosome so bacterial proteins= denatured ie : Gentamicin .
- Used in sepsis , UTIS ,Gram negative organisms ,Staphylococci,
3) Tetracyclines : haults protein synthesis in bacteria as tRNA is not allowed to bind .
- Doxycycline ,Minocycline,Tetracycline
- Chest pathogens
- MRSA
- Chest infections
Inhibitors of nucleic acid synthesis
Zoey 101
Quinolones
- NOT USED often
- levoflaxin,moxifoxacin
- Inhibits DNA grysase ( unwinds DNA in transcription )
- DNA transcription is inhibited
- Metronidazole
- Trimethoprim
Nitrofurantoin
- UTI , E.coli
- Gram negative
Nitrofurantoin is an antibiotic that is used for treating urinary tract infections caused by several types of bacteria.
Nitrofurantoin is converted by bacterial nitroreductases to electrophilic intermediates which inhibit the citric acid cycle as well as synthesis of DNA, RNA, and protein. This drug is more resistant to the development of bacterial resistance because it acts on many targets at once.
Fidaxomicin
-Inhibits RNA polymerase
-used in Clostridium Difficile =prepared orally
-
what antibacterials are used to treat TB ?
what is there mechanism of action ?
RIPE
-Inhibits RNA synthesis
- Rifampicin- binds to RNA polymerase
Obstruction to Formation of cell wall
- Ethambutol stops incorporation of mycolic acid into the cell wall
R-rifampicin
I-isoniazid
P- pyrazinamide
E- ethambutol hydrochloride,
what antibiotics inhibit cell wall formation
1) Beta lactams (penicillins)
2) Glycopeptides (vancomycin)
What antibiotics inhibit protein synthesis ?
50S units : Macrolides ie: clarithromycin , inhibits translocation
30S units : Aminoglycosides (only works aerobically) and tetracyclines
What antibiotic inhibits DNA synthesis ?
1- Quinolones
- act on DNA gryase and DNA Topoisomerase
- stops DNA from unwinding during transcription
Ciprofloxacin and Levofloxacin
what antibiotic can damage DNA ?
1- Metronidazole = treats gram negative ANAEROBIC bacteria
- reduced by anaerobic electron transport chain
- Free radicals are produced and they break down and fragment the DNA
