Anti-microbial Flashcards
Define chemotherapy
Use of drugs (chemicals) to treat a disease
Define antimicrobial drugs
E.g. penicillin
A chemical that interferes with growth (kills or inhibits) of microorganism within a host
Define antibiotic
Of biological origin. Chemical produced by microorganism, that kills or inhibits the growth of another microorganism.
Define chemotherapeutic agent?
Synthetic chemicals
Define selective toxicity
A drug that kills harmful microbes without harming the host
Many newer antibiotics are biological products that are…
Chemically modified or chemically synthesised
What are the 2 main families of bacteria?
Gram +
-has 1 cell membrane
-e.g. staphylococcus aureus
-peptidoglycan (protein chain, with sugar molecules) is exposed + takes
up gram stain
-e.g. bacilli (e.g. aerobic =listeria or anaerobic =clostridium) + cocci (e.g.
staphylococci)
Gram -
- has 2 cell membranes
- peptidoglycan is hidden between membranes, so the gram stain can’t get to it, can’t penetrate cell membrane
- e.g. E. coli, diplococci, coccobacilli
- use lactose fermentation (lactose for energy)
History of chemotherapy…. name 2 drugs developed in 1900s
-Salvarsan (arsphenamine) has arsenic in it, toxic. Developed
against syphillis
-sulphurdrugs (sulphonamide) discovered against gram +bacteria (now
used for UTIs)
Whats the difference between bacteriostatic + bactericidal
Bacteriostatic = stops bacteria reproducing (inhibits bacterial growth)
Bactericidal = actively kills bacteria (e.g. used when treating immunosuppressant pts)
What is the tissue distribution, metabolism + excretion factors of bacteria?
-BBB?
-unstable in acid? (some have to be injected)
-half-life duration? (Often have to take QDS e.g. flucloxacillin, half life
30min)
What are the features of BZs?
- broad spectrum (kills of several species)
- short half-life (30min)
- crosses BBB (used in meningitis)
- bactericidal
- unstable in acid (given IV)
What is the 5 actions of antimicrobial drugs?
- Inhibition of cell wall synthesis e.g. penicillins, cephalosporins
(e.g. cefadroxil, used for UTIs) + vancomycin (last resort, still
some resistance to it, used for septicaemia or endocarditis) - Inhibition of protein synthesis e.g. erythromycin
- Inhibition of nucleic acid replication + transcription e.g. rifampin + quinolones (GABA antagonists)
- Injury to plasma membrane e.g. polymyxin B (problem is that ALL
organisms have one = more likely to affect host). - Inhibition of synthesised of essential metabolites e.g. sulfanilamide
(don’t affect cell wall, just kill of bacteria by paralysing enzymes).
Give an example of drugs that inhibits protein synthesis
Chloramphenicol
- given as eye drops for bacterial conjunctivitis
- wide spectrum
Aminoglycosides
- e.g. gentamicin
- causes non functional proteins to be synthesised
- bactericidal
- narrow therapeutic index + toxicity
- streptomycin used for TB, replaced with rifampicin
Tetracycline
- causes non functional proteins to be synthesised
- used for chlamydia
Macrolides
- e.g. erythromycin
- don’t penetrate BBB - can’t be used to treat meningitis
What’s a beta-lactam antibiotic?
-have a beta lactam ring in their structure
-unstable ring - if there’s a change in shape the molecule falls
apart + doesn’t function. Penicillin mimics an enzyme bacteria needs to
produce its cell wall. The bacteria picks it up, penicillin breaks down =
bacteria can’t synthesis or repair cell wall.
-e.g. penicillin + cephalosporin
-bacteria produce an enzyme called beta lactamase (resistant strains) which breaks down the lactic ring = destroys the antibiotic
What antibiotic is effective against beta-lactamase?
Flucloxacillin, producing staphylococci
The enzyme augmentin destroys beta lactamase (contains penicillin + anti beta lactamase)
What is semisynthetic penicillins?
Made in lab, by adding different side chains onto beta-lactam ring = penicillinase resistant + broader spectrum of activity. E.g. flucloxacillin
What are the 2 main pathogen families?
Candida albicans
-cause yeast like fungal infections in wet areas e.g. oral thrush
Tineal infections
- in moist/between skin area
- ring worm
- second part of name depends where affects body e.g. tinea pedis (ring worm infection of foot)
Treatment
- daktarin cream
- athletes foot cream
What are the 3 main groups of fungi that cause disease?
-moulds (cause infections of skin, nails + hair)
-true yeasts (unicellular, round or oval fungi, can cause pulmonary
infections in immunocompromised pts).
-yeast like fungi (can form non-branching filaments, can cause oral
thrush, vaginitis, endocarditis + septicaemia)
What are the systemic antifungal drugs?
Polyenes
-e.g. amphotericin for systemic fungal infections
Griseofulvin
- from penicillin
- systemic/oral
Imidazoles
-e.g. clotrimazole
Triazolam
-e.g. fluconazole - used orally to treat oropharyangeal + oesophageal
candidiasis + IV to treat systemic candidiasis
Echinocandins
What antiviral drug is used against herpes replication?
Aciclovir are selective inhibition of herpes virus replication
-vaclaciclovir is prodrug
Antiviral drugs are enzyme inhibitors. They either…
- inhibit assembly e.g. indinavir (HIV)
- inhibit attachment (has to attach to cell wall/membrane to get
inside + replicate
-e.g. zanamivir (influenza) inhibits reverse transcriptase of HIV - Inhibit uncoating (viruses need to get out of bacteria/animal cell +
spiral off. E.g. amantadine (influenza) -inhibits protein needed for
uncoating the virus - Inhibits penetration of cell by the virus e.g. AIDS + immunoglobulins
What antiviral drug is used for treating HIV/AIDS?
-antiretroviral (AVR) drugs suppress the replication of HIV in pts
with AIDS (combines 2 nucleoside reverse transcriptase
inhibitors (NRTI) with a non-nucleoside reverse transcriptase inhibitor
(NNRTI), a protease inhibitor or integrate inhibitor
-protease inhibitors - protease splits open viral polypeptide into
functional proteins. By inhibiting this the HIV cannot mature + non-
infectious viruses are produced
-fusion inhibitors
-integrase inhibitors
Antiviral drug enzyme inhibitors …
-interferons (IFNs) prevent the spread of viruses to new cells (viral
hepatitis)
What are the antihelminthic drugs?
-prevent ATP generation + alters membrane permeability (can’t
take in food, so die) of tapeworms
-cause neuromuscular block (can’t function=cause paralysis), inhibit
nutrient absorbtion + paralyses worm in intestinal roundworms
Define parasitism
Relationship in which one biological species lives in a dependent association with another.
What’s a protocyte?
Usually single-cells organisms with a nucleus e.g. amoeba
What is formite transmission?
Viruses/bacteria are transported by touching contaminated surfaces e.g. door handle
How does antibiotic resistance occur to antimicrobial drugs?
- Enzymatic destruction of drug (inactivating enzymes that
destroy drugs) e.g. beta-lactamase produced by staphylococci
inactivate most penicillins + cephalosporins - Prevention of penetration of drug e.g. bacterial cell membrane
becomes impermeable to drug - Alteration of drugs target site (can alter drug binding on bacterial
ribosomes so drug no longer has affinity for drug) - Rapid ejection of drug (development of alternative metabolic
pathways)
How does transferred resistance occur?
-Antibiotic resistance can be carried in plasmids
-the plasmids can be transferred from one organism to another by
conjugation (for,action of tubes between organisms)
-in transduction, plasmid DNA is enclosed in bacterial virus
(bacteriophage) + transferred to another organism.
What does misuse of antibiotics include?
- using outdated or weakened antibiotics
- using for common cold or other inappropriate conditions
- using it in animal feed
- failing to complete prescribed regimen
- using someone else’s leftover prescription
