Antibiotics Flashcards
What are the 2 main mechanisms of antimicrobial action
- Time dependent killing
- Concentration dependent killing
Where do beta lactams act
They act on the cell wall of the bacteria
What is the mechanism of killing in a betalactam
They use time dependent killing
What is the mechansim of elimination
Renal elimination
What is the main adverse effects of beta- lactams
Hypersensitivity
What is the most common resistance method in bacteria against beta lactams
Beta- lactamases: These are enzymes that are able to degrade β-lactam antibiotics and it can not be overcome by increasing the conc.
What is the method of resistance in betalactams that can be overcome by increasing the dose
Mutations in penicillin binding protein, reducing the ability of β-lactam antibiotics to bind and inhibit their activity
How do beta lactams work
They work by binding to Penicillin-Binding Proteins, these Penicillin-Binding Proteins catalyze the final step in peptidoglycan synthesis and so it weaken or increased the cell wall permeability leading to death of the cell
What are the microbe classes that are susceptible to beta lactams
Gram positive and spirochetes
What types of bacteria are susceptible to penicillin 5
Streptococci
Syphilis
Enterococci
Listeria
Actinomyces
What are aminopenicillins and what are the 2 main types
They are subclass of penicillins within the β-lactam class of antibiotics. They are distinguished by an added amino group (-NH2) on the penicillin structure, which enhances their spectrum of activity against certain Gram-negative bacteria while retaining activity against Gram-positive bacteria. They 2 main types are Ampicillin and Amoxicillin
What is the main benefit of Cloxacillin and what bacteria is it used on
It is good at working in beta lactamase enviroments
Which bactria can cloxacillin and flucloxacillin be used in and what is the difference
They are both only able to be used in gram positive patients, the are very simiar flucloxacillin is just better absorbed orally
What are the 2 main beta-lactamase inhibitors
Clavulanate and Tazobactam
What is the benefit to beta-lactamase inhibitors
If used in combination with penicillin they can reverse resistance
What is the drug of choice for Resp tract infections
Amoxicillin
What is the drug of choice for Staph infections
Cloxacillin/flucloxacillin
What are the 2 types of 1st generation cephalosporins and what are they used for
Cefazolin and Cephalexin mainly used for Strep and Staph.
What is the second generation of cephalosporin
Cefuroxime it can be used against Strep, Staph, Haemophilus, community acquired gram negative infections
What are the 2 main 3rd generation cephalosporins and what are they effective against
Ceftriaxone and Ceftazidime effective against Strep, Staph, CAP gram negatives and Haemophilus as well as spirochetes and typhoid
What drug is given as surgical prophylaxis
Cefazolin 1g to prevent Staphylococcal infection
What is the main excretion method used by ceftriaxone
Bile
What is the drug of choice in empirical treatment of bacterial meningitis
Ceftriaxone because of its good CSF penetration
What is the function of a carbapenems
These are very broad spectrum antibiotics that cover most types of infection
Which antibiotic classes fall into the beta lactam family 4
Penicillins, cephalosporins, carbapenems, and monobactams
What are the 3 main manifestations of penicillin allergies
- Maculopapular Rash
- Anaphylaxis
3.Angioedema, Urticaria(hives), and Bronchospasm
What is the mechanism of killing used by Glycopeptides
Time dependent killing
What are the microbes that are killed by glycopeptides
Gram positive bacteria
What is the MOA of glycopeptides
They interfere with the synthesis of the cell wall by binding to specific components of the bacteria peptidoglycan
What is the main glycopeptide used and its side effects
Vancomycin is the main glycopeptide used and the main side effects is that it is nephro and oto toxic
What are aminoglycosides most effective against
Aerobic gram negative bacilli
What is the MOA of a aminoglycoside
They act as bactericidal inhibitors of protein synthesis
What is the mechanism of killing of an aminoglycoside
They kill by concentration dependent killing
What are 2 examples of aminoglycosides
Gentamicin and Amikacin
What is gentamicin used to treat
Pyelonephritis and is often combined with beta lactams for polymicrobial infections or for its synergistic effects
What is the mechanism of action of a quinolone
It targets gyrase and topoisomerase enzymes used in DNA synthesis
What are the signs of toxicity in Quinolones
- Rashes
- CNS disturbances
What are examples of 2nd generation quinolones and what is the uses 1
Ciprofloxacin, They are used in very serious infections and are the drug of choice in conditions like bacterial dysentery and pyelonephritis
What is an example of a 3r generation Quinolone and what is it main use
Levofloxin, MDR TB
What is the MOA of a macrolide
It inhibits the 50s ribosomal component thus inhibiting protein synthesis
What are macrolides most effective against
The are active against gram positive bacteria. and are also used for S. pneumoniae resistance
What is the most common side effect
GIT disturbance
What are 2 examples of macrolides and what is the benefit of the one over the other
Erythromycin and Azithromycin
Macrolides inhibit CYP450 metabolism but azithromycin does not
What is the main therapeutic use of macrolides
They are used in atypical pneumonias like Legionella, Mycoplasma and Chlamydophila
What is the MOA of tetracyclines
They function by inhibiting the synthesis of proteins by inhibiting 30s ribosomes
What are the 2 main mechanisms of resistance in tetracycline
- Efflux
- Enzymatic breakdown
What are the forms of toxicity that occur in doxycycline 3
- Nausea
- Photosensitivity
- Teeth discolouration
Why should tetracyclines be avoided in children
It causes permanent discolouration of the teeth
Which infections are treated with tetracyclines
Rickettsia
Brucellosis
Acne in low doses
What infection can tetracycline be given as prophylaxis
Falciparum malaria
What are the 2 active components in Cotrimoxazole
Sulfamethoxazole and trimethoprim
What is the function of Trimethoprim
Enzyme that reduces dihydrofolic acid to tetrahydrofolic acid, which is needed for the synthesis of nucleotides and ultimately DNA.
What is the function of Sulfamethoxazole
It interferes with the folic acid pathway to thus inflencing the DNA synthesis in bacteria
What is the main side effect of sulphonamide hypersensitivity
Stevens-Johnson Syndrom
What is the main use of cotrimoxazole in HIV patients 3
- Pneumocystis jirovecii pneumonia
- Toxoplasmosis
- Cystoisospora belli diarrhoea
What is the MOA of metronidazole
It is toxic to DNA and forms free radicals in anaerobic metablism
What is the main side effects of long term metronidazole use
Neurotoxic and neutropenia
Which protozoans are affected by metronidazole
- Entamoeba histolytica
- Trichomonas vaginalis
- Giardia lamblia
