Antimicrobial chemotherapy (better cue cards Flashcards
Define ‘bactericidal’
Antimicrobial that kills bacteria
Define bacteriostatic
Antimicrobial that inhibits growth of bacteria
Define ‘sensitive’
Level of anti-microbial required to inhibit/kill organism at infection site
Define ‘resistant’
Organism not killed/inhibited by levels of antimicrobial available at site of infection
Define ‘MIC’
Minimal inhibitory concentration - minimum conc. of antimicrobial needed to inhibit visible growth of given organism
Define ‘MBC’
Minimal bactericidal conc. - Minimum conc. of antimicrobial needed to kill organism
What are the 3 routes of administration
Systemic - taken internally
Topical - Applied to surface, eg skin
Parenteral - Administered intra-venously (iv) / intra-muscularly (im)
What are the 3 mechanisms of action of antimicrobial agents
Inhibition of cell wall synthesis (humans don’t have cell walls)
Inhibition of protein synthesis
Inhibition of nucleic acid synthesis
What do Beta lactams Do
Disrupt peptidoglycan synthesis
Inhibiting Penicillin-binding proteins
Peptidoglycan Important structure of bacteria cell wall
what two types of drugs are β-lactams
Penicillin
Cephalosporins
What are the two types of antimicrobials which inhibit cell wall synthesis
Glycopeptides and β-lactams
What are two common glycopeptides
Vancomycin
Teicoplanin
Describe the mechanism and range of action of glycopeptides
inhibit cell wall synthesis - but at a prior stage than B-lactams
Act only on gram positive organisms
What route of administration must glycopeptides take (unless special circumstances)
Parenterally (iv/im)
What is one side effect of vancomycin
It is toxic
What are the 4 types of antimicrobials which inhibit protein synthesis
- Aminoglycosides - gram -ve
- Macrolides and tetracyclines - gram +ve
- Oxazolidinones - gram +ve
- Cyclic lipopeptides - gram +ve
What type of bacteria are aminoglycosides useful for?
Treating serious gram negative Infection
What type of drug is gentamicin and what is a common side effect of adminsitration
Aminoglycoside and is toxic -
Requires careful dosing regime & monitoring of levels
What are the uses of macrolides and tetracyclines
Treatment of gram positive infections in patients who are penicillin allergic CANNOT BE USED WITHOUT LABORATORY TESTING
What class of drug is linezolid and what is it commonly used for?
oxazolidonones (protein synthesis inhibitor).
good activity against MRSA
Can be given orally
What class of drug is daptomycin and what it is commonly used for?
Cyclic lipopeptide (protein synthesis inhibitor).
Activity against gram positives in general and MRSA
What are the 2 classes of drug which inhibit nucleic acid synthesis
Trimethoprim
Sulphamethoxazole
Used in combination to form a drug
- Co-trimoxazole
- Fluoroquinolone’s
What type of drug is ciprofloxacin? What it is commonly used for? What are some of the drawbacks of the drug
Fluoroquinolone (nucleic acid inhibitor).
used against gram negative organisms.
Taken orally
Not to be used in children
Describe inherent or intrinsic resistance
All strains of a given species naturally resistant to antibiotic
Due to inability of drug to penetrate bacterial cell wall
What are the 2 ways in which acquired resistance may be acquired?
- A spontaneous mutation
- Genes that code for resistance spread from organism to organism through plasmids
What are the 2 mechanisms of resistance to β–lactam antibiotics?
- β-lactamase production - enzymes which cleave β–lactam ring of antibiotic & render it inactive
- Alteration of penicillin binding protein (PBP) target site - Mutations in PBP genes result in a modified target site
B-lactams no longer bind
2 ways to combat B-lactamase?
- Co-amoxiclav plus the B lactamase inhibitor clauvanic acid
- Flucloxacillin - modified form of penicillin
What are ESBL’s and what are the implications of their existence
Extended spectrum β–lactamases (ESBLs)
Produced by Gram negative organisms.
Break down third generation cephalosporins & penicillins
Render organism resistant to all β–lactam antibiotics
What glycopeptide resistant bacteria has appeared recently and what are the implications of this mutation?
Vancomycin resistant enterococci (VREs)
Major problem: Resistance might spread from enterococci to Staph aureus producing vancomycin resistant staph aureus
Describe the spectrum of Benzyl penicillin (penicillin G)
Gram +ve organisms
intra-venous treatment of serious pneumococcal, meningococcal and strep pyogens
Describe the spectrum of amoxicillin/ampicillin
Gram -ve activity
Oral absorption
Effective against streptococci and coliforms
Describe the spectrum of co-amoxiclov
Effective against B-lactamase producing coliforms
Describe the spectrum of flucloxacillin
Effective against staph infections
Describe the spectrum of piperacillin
Gram -ve cover
Effective against Enterococcus faecalis and pseudomonas species
Describe the spectrum of cephalosporins
Activity against Gram -‘ve organisms increases from 1st through 3rd generation
Activity against Gram +’ve organisms decreases from 1st through 3rd generation
Generally not used as encourage C Diff infections
How must cephalosporins be taken?
Parenteral use only
Describe the spectrum of aminoglycocides
Noted for action against Gram -ve organisms
Effective against staphlococci but not streptococci
Gentamicin cheapest and most common aminoglycocide
Describe the spectrum of glycopeptides
Only gram +’ve organisms are affected (anaerobic +aerobic)
Vancomycin most common example
Describe the spectrum of action of macrolides
Mainly used against gram +’ve organisms -
Alternative to penicillin for patients with a penicillin allergy
Describe the spectrum of action of Quinolones
Nearly all gram -‘ve organisms are sensitive
Mainly used in treatment of community acquired pneumonia
Describe the spectrum of action of metronidazole
Effective against Gram +’ve and -‘ve anaerobes
Describe the spectrum of action of fusidic acid
staphylococcal drug
Describe the spectrum of action of trimethoprim
Used in urinary infections
Describe the spectrum of action of tetracyclines
Used in genital tract and respiratory tract infections
Describe the spectrum of action of clindamycin
Effective against Gram +’ve organisms
What infection is linezolid used against
MRSA
What infection is fidaxomicin used against
C. diff
What infection is daptomycin used against?
MRSA
What are the 4 classes of anti-fungal drugs?
Polyenes
Azoles
Allylamines
Echinocandins
Describe the mechanism of polyenes
Bind to the ergosterol- present in fungal wall
Also binds to mammalian sterols making polyenes TOXIC
Describe the use of amphotericin B and Nystatin (Hint: they are Polyenes)
Amphotericin B is used intra-venously for serious yeast infections and other fungal infections. Very toxic.
Nystatin is used topically or in oral suspension and is not an intra-venous agent for serious fungal infection
Describe the mechanism of Azoles
Inhibit ergosterol synthesis
What is fluconazole used to treat?
Yeast infections
What are voriconazole and intraconazole used to treat?
Yeast and filamentous fungi including: Aspergillosis
Describe the mechanism of allylamines
They suppress the ergosterol synthesis but act at a different stage of the synthetic pathway from azoles
Describe the use of Terbinafine
Used for fungal infections of the skin and nails
Describe the mechanism of echinocandinds
They inhibit the synthesis of glucan polysaccharide in several types of fungi
What are echinocandins used for?
Serious candida and aspergillus infections
Describe anti-herpes virus drugs
All become latent and include: Herpes simplex virus (HSV), eptein-barr virus (HBV), cytomegalovirus (CMV) and Varicella-Zoster Virus (VZV).
Describe the mechanism and function of Aciclovir
not very toxic
Extremely active against HSV and active against VZV
Intravenously used for serious,
Oral for less serious
Describe the use of valaciclovir and famciclovir
Related to aviclovir - Used in oral treatment of HSV and shingles
Describe the use of valganciclovir
Pro drug of ganciclovir -> alternative treatment for CMV.
High levels of bone marrow toxicity
Describe the use of foscarnet
Used for HSV, VZV and CMV
Highly nephrotoxic
Describe the use of Cidofovir
Used for CMV retinitis
What anti-viral agent is used to treat infections with HIV?
Saquinavir
