Antimicrobials + Antimicrobial resistance Flashcards
what parts of a pathogen do the most effective antibiotics target?
most successful antibiotics hit only three targets or pathways:
◊ The ribosome (which consists of 50S and 30S subunits)
◊ Cell wall synthesis
◊ DNA gyrase or DNA topoisomerase
what is the difference between bacteriostatic and bactericidal
bacteriostatic= stops bacteria from reproducing (drugs like these stop the growth and we leave the body to kill it)
e.g. chloramphenicol, tetracyclines, macrolides, trimethoprim, clindamycin
bactericidal= kills the bacteria
e.g. penicillins, cephalosporins, ciprofloxacin, VANCOMYCIN its a type of glycopeptides (used for sepsis), monobactams
n.b. in the clinic most antibacterials are better described as potentially being both bacteriostatic and bactericidal.
Depending on the:
► dose
► duration of exposure
► the state of the invading bacteria
antibiotics such as
*beta lactams e.g. penicillins, cephalosporins,carbapenems, monobactams
*vancomycin
*bacitracin
*glycopeptides
what part of the bacteria do these antibiotics target?
antibiotics such as
*beta lactams e.g. penicillins, cephalosporins,carbapenems, monobactams
*vancomycin= inhibits cell wall biosynthesis by targeting the d-Ala-d-Ala terminus of peptidoglycan (PG)
*bacitracin
*glycopeptides
target bacterial cell wall synthesis
antibiotics in the class ‘polymyxins’ target which component of the bacteria
polymyxins target the cell membrane of bacterial cells in gram -ve bacteria
what do the following antibiotics target on a bacteria:
*sulfonamides
*trimethoprim
these target folate synthesis
what do the following antibiotics target on a bacteria:
*quinolones
*Rifampin
these antibiotics target nucleic acid synthesis;
*quinolones (targets DNA gyrase)
*Rifampin(targets RNA polymerase)
what do the following antibiotics target on a bacteria:
*macrolides
*clindamycin
*linezolid
*chloramphenicol
*streptogramins
*tetracyclines
*aminoglycosides
all of these target PROTEIN SYNTHESIS IN BACTERIA i.e. it attacks the ribosome
*macrolides
*clindamycin
*linezolid
*chloramphenicol
*streptogramins
=these target 50S subunit
*tetracyclines
*aminoglycosides
=these 2 target the 30S subunit
a bacteria synthesises its cell wall made of peptidoglycan with an enzyme called ____. What common antibiotic targets this enzyme?
a bacteria synthesises its cell wall made of peptidoglycan with an enzyme called transpeptidase (it cross links the peptidoglycan cell wall to make it strong)
BETA LACTAMS INTERFERE WITH THIS TRANSPEPTIDASE ENZYME + STOP CELL WALL SYNTHESIS
beta lactams; penicillins, cephalosporins,
carbapenems, monobactams
how do glycopeptide antibiotics, such as vancomycin and teicoplanin kill bacterial cell walls?
*heptapeptide antibiotics are effective AGAINST GRAM +VE BACTERIA ONLY;
inhibit cell wall synthesis by forming H-bonds w the D-ala-D-ala cell wall so they bind to PRECURSOR (unlike beta lactams which target ezyme transpeptidase)
How do polymyxins antibiotics work?
polymyxins are for gram
-ve bacteria only!
these bind to LPS (lipopolysaccharide); polymyxins do this by competing and displacing cations (Ca2+ and Mg2+) from phosphate– this allows them to bind to lipopolysaccharide (LPS)
what is the difference between gram -ve and gram +ve bacteria
major difference between the two groups of bacteria is the thickness of the cell wall and the presence of an outer membrane in Gram negative bacteria only. The bacterial cell wall ranges from 20–80 nm thick for Gram positive and between 1.5–10 nm thick for Gram negative bacteria.
n.b. NEGATIVE GRAM ARE WORSE/harder to kill (NEGATIVE=BAD)
How do aminoglycosides (antibiotics) work?
e.g. gentamicin, amikacin, tobramycin, neomycin, and streptomycin
aminoglycosides are bactericidal
they can work on gram +ve and -ve bacteria
they inhibit protein synthesis by binding, with high affinity, to the A-site on the 16S ribosomal RNA of the 30S ribosome
- tetracylcines (e.g. doxycycline, minocycline)
*macrolides (e.g. erythromycin, clarithromycin) and lincosamides (e.g.clindamycin)
these all inhibit protein synthesis by attacking ribosomes; which part do they affect?
these antibiotic groups are all are bacteriostatic
*tetracylines bind to 30S prevent tRNA interacting with the mRNA-ribosome complex
*macrolides + lincosamides bind to 50S prevent translocation of polypeptide chain along ribosome
quinolones/fluroquinolones (e.g. ciprofloxacin, levofloxacin) are antibiotics which inhibit _____
quinolones/fluroquinolones are antibiotics which inhibit nucleic acid synthesis
- broad spectrum- bactericidal SYNTHETIC ANTIMICROBIALS
*inhibit DNA synthesis + promote DNA cleavage by binding to:
-topoisomerase II (DNA gyrase)
* topoisomerase IV (DNA topoisomerase)
what is the action of Rifampicin antibiotic
Rifampicin= antimicrobial inhibitor of prokaryotic transcription initiation
* treats diverse mycobacterial infections and gram-positive bacterial infections
mechanism:
*Only binds to bacterial DNA dependent RNA polymerase
*Inhibits RNA polymerase in bacterial cells (especially Gram-positive)
*It is lipophilic and good candidate for treating TB meningitis as it an cross the blood-brain barrier
*Used in combination with other drugs to treat Mycobacterium tuberculosis and some staphylococcal infections