Antimicrobial Chemotherapy Flashcards
Bactericidal
kills bacteria
Bacteriostatic
will inhibit growth of bacteria
MIC
minimum inhibitory concentration
MBC
minimum bactericidal concentration
Topical administration
applied to a surface e.g. skin or mucous membranes
Systemic administration
taken internally either orally or parenterally
Parenteral administration
IV or intramuscularly
What 3 sites do antibiotics act on?
cell wall synthesis
protein synthesis
nucleic acid synthesis
Cell wall synthesis inhibitors
……
Name 2 drugs that will inhibit cell wall synthesis.
penicillins
cephalosporins
(beta lactams)
How do beta lactams inhibit cell wall synthesis?
inhibit enzymes that cause the cross linking of the peptidoglycan chains
What penicillin is effective against enterococcus faecalis and pseudomonas species and some anaerobes?
piperacillin
Name 2 carbapenem family (related to penicillins) drugs that have the widest spectrum of all and are effective against nearly all bacteria, including anaerobes?
meropenem and imipenem
How is the activity of cephalosporins against gram negative organisms affected as the generation number increases?
the activity increases
How does cephalosporin activity against gram positive organisms change as generation number increases?
the activity decreases
What is the name of another class of antibiotics that inhibit cell wall synthesis?
glycopeptides
How do glycopeptides inhibit cell wall synthesis?
They inhibit the formation of a peptidoglycan precursor.
Give examples of glycopeptide antibiotics.
vancomycin and teicoplanin
How are glycopeptides administered?
parenterally
Give a limitation of glycopeptide antibiotics.
can only act on gram positive infection as cannot penetrate gram negative cell wall
What is a common problem with vancomycin?
toxicity
What drug would be used to treat a serious MRSA infection?
intravenous vancomycin
What is ampicillin?
a broad spectrum penicillin
Inhibition of Protein Synthesis
….
There are 4 groups of protein synthesis inhibiting antibiotics. Name them.
aminoglycosides
oxazolidinones
cyclic lipopeptides
macrolides and tetracyclines
Give an example of an aminoglycoside, how it is administered and state an issue with it.
gentamicin
parenterally
toxic
What type of bacteria are aminoglycosides particularly useful in treating?
serious gram negative infections including pseudomonas
What are important side effects of aminoglycosides?
nephrotoxicity
otoxicity (to the ear)
Macrolides and Tetracyclines.
Give 2 examples of macrolides and what they are used for.
clarithromycin
erythromycin
used in penicillin allergic patients to treat gram positive infection
What conditions are macrocodes also commonly used to treat?
early stage syphillis
uncomplicated genital chlamydia infection
What macrolide drug is effective for single dose treatment of chlamydia infection?
azithromycin
10% of which types of bacteria are macrolide resistant?
streptococcus pyogenes
staphylococcus aureus
streptococcus pneumoniae
Give an example of an oxazolidinone.
How is it administered? What is it effective against? When is it used?
linezolid
administered orally
effective against MRSA
held in reserve for use in serious infection
Give an example of a cyclic lipopetide. What is it used against? When is it used?
daptomycin
gram positive bacteria, particularly MRSA
held in reserve for use on specialist advice
Inhibitors of Nucleic Acid Synthesis
….
Name the two classes of nucleic acid inhibiting antibiotics.
trimethoprim and suxamethoxazole
fluoroquinolones
What do trimethoprim and suxamethoxazole do?
Trimethoprim on its own can be used to treat UTI
A combined drug of trimethoprim and suxamethoxazole called co-trimoxazole is used it the treatment of respiratory tract infections as it is less likely to cause C.diff infection.
Give an example of a fluoroquinolone, what it does and what it is effective against.
ciprofloxacin
inhibits DNA synthesis more directly
effective against gram negative organisms
Which group cannot be prescribed ciprofloxacin and why?
children
danger of interference with cartilage growth
What range of bacteria are quinolone effective against?
nearly all gram negative infections inculding pseudomonas
Antibiotic Resistance
….
Beta lactam resistance is characterised by 2 mechanisms. What are they?
- produce beta lactamase which can cleave the beta lactam loop which is the active component in penicillins and cephalosporins e.g staph. aureus
- have an altered penicillin binding site, therefore drugs can no longer bind to the organisms to have an effect e.g MRSA
What beta lactam antibiotic can be used to overcome organisms such as s.aureus that can produce beta lactamase?
flucloxacillin - is beta lactamase resistant
What drugs is MRSA resistant to?
all beta lactams
What are ESBLs? (extended spectrum beta-lactamases)
chemicals produced by some gram negative organisms rendering them resistant to beta lactam agents
How is glycopeptide resistance characterised?
the peptidoglycan precursor to which vancomycin normally binds has an altered structure therefore cannot bind
How common is vancomycin resistance in gram positive bacteria?
very rare, however vancomycin resistant enterococci have appeared recently
What is the concern with vancomycin resistant enterococci?
that they will pass their mechanism of resistance on to s.aureus
Describe one other antibiotic resistance mechanism.
blocking transport of drug into cell or actively pumping it out
What drug could you give to treat a serious infection with a gram negative organism such as E.coli?
IV Gentamicin
Antifungal Drugs
….
What 2 groups can fungi be divided into?
filamentous fungi (moulds) yeasts
Name the different classes of anti fungal drugs.
azoles
polyenes
allylamines
echinocandins
What fungi are polyenes effective against?
both yeasts and filamentous fungi
How do polyenes combat fungi?
by binding to ergosterol which is present in the fungal cell wall
What is amphotericin B used for and how is it administered?
serious fungal infection
intravenously
What is an issue with amphotericin B?
it is toxic
What polyene drug is used topically and in oral suspension?
nystatin
Give examples of when nystatin would be used clinically.
creams for skin fungal infections
pessaries for vaginal candida infections
What do azoles do?
inhibit ergosterol synthesis
What azole drug is used to treat yeast infection but not filamentous fungi infection?
fluconazole
What two azole drugs can treat Aspergillosis?
voriconazole and itraconazole (VAI)
What do allylamines do?
inhibit ergosterol synthesis at a different stage to the azoles
What is the name of the only allylamine in common clinical use?
terbinafine
What is terbinafine used to treat?
mainly dermatophytes (ringworm infections and athletes foot)
What do echinocandins do?
inhibit synthesis of glucan polysaccharide in several types of fungi
When are echinocandins used?
for serious aspergillus and candida infections
Anti-Viral Drugs
…
What are 4 main herpes viruses?
herpes simplex virus
epstein-barr virus
varicella zoster virus
cytomegalovirus
What is an important feature of all herpes family viruses?
they become latent
Name a drug that is effective against HSV and VSV.
aciclovir - oral
How does aciclovir work?
It is a nucleoside analogue that will become active by an enzyme coded for by the virus genome
How can aciclovir be administered?
IV - serious infections such as VZV pneumonitis
orally-cold sores
topically - cold sores
Name a drug involved in HIV therapy.
saquinavir
What is the name of the first drug treatment for HIV and how did it work?
zidovudine
nucleoside analogue that interfered with the action of reverse transcriptase
What is now common practice in the treatment of HIV?
using a combination of 3 drugs active at different stages of DNA replication
How do we monitor a patient’s response to anti-HIV drugs?
viral load
CD4+ cell count
What is a problem with the anti-HIV drugs?
toxic
What protein produced naturally by the immune system but made available clinically by genetic engineering is used to treat selective hepatitis B and C infections?
interferon alpha
What factors have limited the use of interferon alpha as a treatment for Hep B and C?
ineffective on its own
serious side effects
expensive
What drug, mainly used for HIV treatment, is also used for treatment of Hep B?
lamivudine - given orally
What is a common treatment for hepatitis C?
combination therapy of ribavarin and interferon alpha
Name 2 common viral respiratory infections.
Influenza A
Influenza B
What 2 drugs are licensed to treat Influenzas A and B within 48 hours of onset of symptoms?
zanamavir and oseltamavir (ZOI)
UTI Agents
…
What 2 drugs are used in the treatment of lower urinary tract infections?
nalidixic acid - only gram negative aerobes
nitrofurantoin - gram negative and some gram positive
What group of drugs are allergic reactions most often associated with?
beta lactams
What is an important side effect of antibiotic therapy?
C.diff infection
What is C.diff infection treated with?
oral metronidazole or oral vancomycin
Use of what group is most commonly related to renal toxicity?
aminoglycosides
When antimicrobials are used in combination there are 3 possible outcomes. What are they?
- effects are additive
- effects are antagonistic
- effects are synergistic
What is the general outcome of two cidal drugs or 2 static drugs?
additive or synergistic
What is the general outcome of combining one tidal and one static drug?
antagonism
What is an ‘E-test’?
a way to measure MIC of one antibiotic against another. It is a paper strip test.
