Antimicrobial chemotherapy Flashcards
What does bactericidal mean?
Antimicorbial that kills bacteria
What does bacteriostatic mean?
Antimicrobial that inhibits the growth of bacteria but does not kill them
A strain of bacteria that is killed/inhibited by an antimicrobial at the site of infection is …
Sensitive
What does it mean if a strain of bacteria is resistant?
It is not killed/inhibited by that antimicrobial
What is the MBC?
Minimal bactericidal concentration - minimum concentration of a given bactericidal antimicrobial needed to kill a given bacteria
What is the MIC?
Minimal inhibitory concentration - minimum concentration of an bacteriostatic antimicrobial needed to inhibit the growth of a given bacteria
What are the 3 routes of administration of anitbiotics?
Topical
Oral
Parenteral - IV, IM or sub-cutaneously (sometimes)
What are the 3 ways that an antibiotic can kill bacteria?
Inhibit cell wall synthesis
Inhibit protein synthesis
Inhibit nucleic acid synthesis
What are the types of antibiotics that target cell wall synthesis, and how do they work?
Beta-lactams:
- Inhibit enzyme that cross links PG cell wall
Glycopeptides:
- Inhibit assembly of peptidoglycan precursor
Give the 2 types of Beta-lactams
Penicillin
Cephalosporins
Give the 2 types of glycopeptides
Vancomycin
Teicoplanin
What are the types of protein synthesis inhibitors?
Aminoglycosides
Macrolides
Tetracyclines
Oxazolidinones
Cyclic lipopeptides
Describe how aminoglycosides work.
Insert the wrong amino acid in chain during translation
Gentamicin
Describe how Macrolides work
Prevent formation of peptide bonds between amino acids during translation
Erythromycin
True of false
Macrolides, like erythromycin, are used to treat gram negative infections, if the patient is allergic to penicillin
False
It is used as an alternative to penicillin for treating gram POSITIVE infections
Tetracyclines are another type of antibiotic.
How do they work?
Stop codon - anticodon binding by tRNA during translation, thus stopping protein synthesis
Give an example of an oxazolidinone, and describe how they work.
Linezolid
Cleaves the ribosome into two pieces
Which class of protein synthesis inhibiting antibiotic works by changing the curvature of the bacteria membrane?
Cyclic lipopeptides
Changes curvature, creating holes which ions leak out/in through
Depolarization and loss of membrane potential
Protein, DNA, RNA synthesis all stops so the bacteria dies
Give an example of a cyclic lipopeptide
Daptomycin
What drug is used to inhibit purine synthesis?
Trimethoprim and sulphamethoxazole
Together = co-trimoxazole
What are purine synthesis inhibitors used to treat?
UTI
Chest infections (as an alternative to cephalosporins)
Fluoroquinones are a type of…
Nucleic acid synthesis inhibitor
How are fluoroquinones administered?
Orally and parenterally
Fluoroquinones are particularly effective against Gram _____ organisms
Negative
What demographic is unsuitable for treatment using fluoroquinones?
Children
Interferes with cartilage growth
Gram negative organisms are always resistant to what antibiotic?
Vancomycin
How do bacteria acquire resistance?
Via spontaneous mutation
or by receiving resistance genes from other bacteria via plasmids or transposons
Describe the problems being caused by Beta-lactamase
Beta-lactamase is an enzyme produced by some strains of bacteria
It cleaves the B-lactam ring of the antibiotic
thus it becomes ineffective
Common with gram negative bacteria and most hospital strains of Staph. aureus
Why is alteration of the penicillin binding protein (PBP) target site a problem?
B-lactams target this to prevent cross bridge formation, which would stop cell wall synthesis
Mutations mean that penicillin and cephalosporins are unable to bind to this
Methicillin resistant staph aureus (MRSA) is an example of a bacteria type with this alteration
Aminoglycosides can only be administered…
Parenterally
Give a commonly used aminoglycoside
Gentamicin
Glycopeptides, such as vancomycin, are used to treat gram _____ bacteria that are both _____ and ______
Gram positive
Both aerobic and anaerobic
Erythromycin is:
A) a macrolide, used to treat gram negative and positive organisms
B) a macrolide, used to treat only gram positive bacteria and never gram negative
C) a glycopeptide, that only treats gram negative bacteria
D) a macrolide, that is mainly used to treat gram positive organisms
D
Erythromycin is a type of macrolide
Mainly used to treat gram positive organisms, as an alternative to penicillin
Quinolones are active against what type of organisms?
Gram negative
Only treatment option against pseudomas
Metronidazole is effective against ______, both gram positive and negative
Anaerobes
Fusidic acid targets a specific species of bacteria. What is this species?
Staphylococcus
Trimethoprim is used to treat what type of infection?
Urinary tract infection
Also chest infections when given with other antibiotics
Staphylococci and streptococci are both types of gram _____
Gram positive bacteria
What are some common side effects produced by anti-microbials?
Gastrointestinal problems Thrush Liver toxicity Renal toxicity Neurological toxicity Haematological toxicity
What is monotherapy?
Treatment using only one antimicrobial drug
WHat are the general rules regarding if a combined treatment will be additive, synergistic or antagonistic?
Two bactericidal or two bacteriostatic = additive or synergistic
One of each = antagonistic
What is the simplest test, used in labs to determine the MIC?
E-test
Polyenes are a type of anti-fungal drug.
Describe why they are effective on fungi but not bacteria
Polyenes bind to ergosterol
Ergosterol is present in fungal cell walls, but not bacterial cell walls
Why are polyenes toxic?
They bind to other ‘sterols’ as well as ergosterol
Thus they can bind and have an effect on cholesterol on the surface of human cells
How do azoles work?
Inhibit ergosterol synthesis
so Fungal cell wall can’t be synthesised
How do allylamines work?
Suppress ergosterol synthesis (at a different stage to azoles)
How do echinocandins work?
Inhibit the synthesis of glucan, a polysaccharide needed by many types of fungi
What are the types of virucidal drugs?
There aren’t any
All anti-virals are virustatic (stop growth/replication)
You can’t kill a virus
Aciclovir targets what family of viruses?
Herpes
In general, anti-herpes drugs follow what naming rule?
They end in ‘ovir’
Valicicl’ovir’
Interfero A is a protein that is used to treat what disease?
Hep B and C
Benzyl penicillin is used to treat Gram _____ bacteria
Gram positive bacteria
Amoxicillin & ampicillin can be used to treat Gram ______ infections
Gram negative
What is Co-amoxiclav made up of, and what is it used to treat
Amoxicillin & beta lactamase enzyme inhibitor
Used to treat Beta lactamase producing coliforms
What is flucloxacillin used to treat
Staphylococcal bacterial infections
Piperacillin is used to treat Gram _____ bacteria
Gram negative
What are imipenem & meropenem?
Carbapenems
close relatives of penicillins
Cephradine, cefuroxime, ceftriaxone & ceftazidime are all types of ____
Cephalosporins
Beta lactams
