Antibiotics Flashcards
Explain the different names for antibiotic effects on bacteria.
Bactericidal- kill bacteria
Bacteriostatic- inhibit growth of bacteria.
Explain the different antibiotic spectrum.
Broad spectrum- larger number of bacteria species
Narrow spectrum- limited number of bacteria
Limited spectrum- one species.
Explain the characteristics of bacteria.
Toxic only to bacteria.
Innocuous to humans- little to no side effects.
Explain the cell wall of bacteria.
Humans do not have a cell wall, it is a bacteria specific organelle
Responsible for integrity and protection.
Main target for antibiotics
No CW= death by autolysis.
What is unique about bacteria that stain purple?
They are gram positive bacteria with a thick layer of peptidoglycan.
Easier to target than gram- due to the thick chains between the peptidoglycan.
List a number of antibiotics that act on peptidoglycan biosynthesis.
Penicillin
Chephlaosporin
Carbapenems.
Vanomycin.
Explain B-lactam antibiotics.
Effective against growing and dividing cells.
Bactericidal
Inhibit transpeptidase cross-linking reaction.
What is a limitation of B-lactam antibiotics.
Resistant bacterial species produce B-lactamse- an enzyme that inactivates antibiotics by breaking down their B-lactam ring.
What are examples of B-lactam antibiotics?
Penicillins- drugs that end in cilin.
Cephlaosporins- drugs that start with cef.
Carbapenems- drugs that end in penem.
What are the key characteristics of penicillins?
Bactericidal
Very effective against G.negative.
What are the key characteristics of cephlaosporins?
Bactericidal
Effective against gram positive and negative bacteria.
Can be anaerobes.
What are the key characteristics of carbapenems?
Bactericidal
Broad spectrum drug
Administered IV.
Affective against all but MRSA and VRE.
Explain vancomycin.
Inhibitor of CW biosynthesis.
Glycopeptide antibiotic.
Administered IV.
Effective against MRSA however there are emerging cases of VRSE and VRE resistance.
Explain antibiotics that inhibit protein synthesis.
Broad spectrum- effective against positive and negative.
Most are bacteriostatic.
Associated with toxicity because mitochondrial ribosomes are inhibited too.
What are examples of antibiotics that inhibit protein components of 30S subunit?
Tetracycline
Aminoglucosid (gentamycin and streptomycin)
What are examples of antibiotics that inhibit protein components 50S.
Macrolides (erythromycin)
Chloramphenicol.
Explain fluoroquinolones.
Antibioitics that inhibit DNA biosynthesis.
Borad spectrum drugs that inhibit DNA gyrase.
Effective against gram negative bacteria and intracellular pathogens.
High toxicity
What are examples of fluoroquinolones?
Ciprifloxacin
Norfloxacin
Drugs that end in floxacin.
Explain rifampicin.
Antibiotics that inhibit RNA biosynthesis in bacterial RNA.
Used predominantly in the treatment of TB.
Explain the target of nucleic acid in biosynthesis.
The biosynthesis of nucleotides requires folic acid.
Anti-metabolites target and inhibit folic acid synthesis.
Explain sulfonamides.
Anti-metabolites.
Analogue of PABA- inhibits dihydropteroate syntheses.
Explain trimethoprim.
Antimetabolites.
Inhibits dihydrofolate reductase.
Explain co-trimoxazole.
Combination of sulphonamides and trimethoprim.
What antibiotics are produced by fungi?
Penicillin and cephlaosporin.
What antibiotics are produced by bacteria?
Erythromycin, rifampicin, streptomycin and tetracyline.
What antibiotics are semi-synthetic?
Ampicillin.
What bacteria are synthetic?
Sulfonamides and trimethoprim.
What does the choice of antibiotic treatment depend upon?
Bacterial species Susceptibility to drug Site of infection Safety of drug Cost of therapy Patient factors.
Resistance to antibiotics arises due to?
Mutation of gene encoding targets of common antibiotics (VGT).
Transfer between organisms of resistant genes carried by plasmids (HGT)
Biofilm formation.
Biochemical resistance is manifested by..?
Decreased accumulation of the drug.
Enzymatic inactivation.
Where do superficial mycoses affect?
Scalp, nails, mucous membranes (mouth and vagina).
Are non-lifethreatening.
Where do systemic mycoses effect?
Internal organs- lung, kidney, brain.
Can be fatal in immunocompromised patients.
What puts a patient at a higher risk of fungal infections?
HIV, organ transplant, long term antibioitics, premature birth, cancer, mestrual cycle.
What are echinocandins?
Anti fungal drug that inhibits gluten synthetase.
Fungicidal
What are examples of echioncandins?
Caspofungin
Micafungin.
What are the target for most antifungals?
The plasma membrane.
What are the actions of antifungals that target the plasma membrane?
Target ergosterol.
Explain polyene antifungals.
Bind to resident ergosterol and form pores in the plasma membrane. The poor disrupt the membrane integrity killing the cell.
Fungicidal.
What is a disadvantage of polyene antifungals?
Prolonged use can lead to kidney failure.
List examples of polyene antifungals.
Amphotericin B.
Nystatin
Both are of natural origin.
Explain azoles.
Ergosterol biosynthesis inhibitors.
Inhibit Lanosterol C14.
Fungatisitc.
What are two types of azalea antifungals?
Imidazole and triazole.
Triazole has a higher affinity for enzymes so is therefore more potent.
What are examples pf allylamnes?
Drugs that end in fine.
Explain flucytosine.
Taken up my fungal cells and are metabalised into 5-FU.
5FU inhibit fungal DNA and RNA.
Commonly used in combination with azoles.
Resistance to antifungal durgs is caused by?
Decreased accumulation of the drug
Inactivation of the drug
Mutation in drug encoding genes
Biofilm formation.
