Antibiotics Flashcards
What 3 classes of antibiotic are ß-lactam antibiotics?
Penicillins
Cephalosporins
Carbepanems
What are the 2 types of antibiotic?
Bactericidal - kills bacteria
Bacteriostatic - slows bacterial growth
What is the target of a ß-lactam antibiotic?
Penicillin Binding Proteins
How are peptidoglycan chains joined?
Transpeptidases cleave terminal D-alanine D-alanine, releasing energy for the formation of peptide bonds
How do ß-lactams work?
The ß-lactam ring mimics the D-alanine D-alanine cross link. It permanently binds to transpeptidase so prevents formation of more cell wall.
What are some advantages of penicillins?
They have very few side effects
They are safe in pregnancy
They are excreted safely by the kidneys
What are some limitations of penicillins?
Patients can often be allergic
Rapid excretion means many doses are required
Bacteria can develop resistance to penicillins
What is an example of a gram +ve penicillin?
Flucloxicillin
What are examples of gram +ve and -ve penicillins?
Amoxicillin
Pipericillin
Phenoxymethylpenicillin
What is Co-amoxiclav?
A compound made up of Amoxicillin and Clavulonic acid
What is a ß-lactamase?
A compound that breaks down the ß-lactam ring
What is the function of clavulonic acid?
It is an inhibitor of ß-lactamase so prevents the degradation of penicillins
What is the function of tazobactam?
It is an inhibitor of ß-lactamase so prevents the degradation of penicillins
What is Tazosin?
A compound formed from Pipericillin and tazobactam
What is an example of a gram -ve penicillin?
Temocillin
What are the 3 principle compounds of penicillin?
Benzylpenicillin - Intravenous
Phenxymethylpenicillin - Oral
Benzathine penicillin - Intramuscular
Which 2 species are targeted by flucloxicillin?
Streptococci and staphylococci
What is MRSA?
Methicillin (Flucloxacillin) Resistant Staphylococcus aureus
What infections can be treated by flucloxacillin?
Skin and soft tissue infection
Wound infections
Cellulitis
What is cellulitis?
An infection of the soft tissue beneath the skin
What organisms are targeted by Temocillin?
Coliforms e.g. E.coli, salmonella, enterobacter
Very useful against ESBLs
What is an ESBL
An Extended Spectrum ß-Lactamase
What are the advantages of Cephalosporins?
They have a longer half-life in plasma
Reduced risk of allergy
More resistant to ß-lactamases
Safe in pregnancy
What are the disadvantages of cephalosporins?
They kill a large portion of the normal gut flora, which allows the growth of Clostridium difficile infections
Does a 1st generation cephalosporin have a broader spectrum than a 4th?
Yes
What are examples of 1st generation cephalosporins?
Cefalexin
Cefalozin
What are examples of 2nd generation cephalosporins?
Cefuroxime
Cefaclor
What are examples of 3rd generation cephalosporins?
Ceftrioxone
Cefixime
Cefotaxime
Ceftazidime
What is an example of a 4th generation cephalosporin?
Cefepime
How do Glycopeptide antibiotics work?
They bind to D-alanine-D-alanine terminal ends and block transpeptidase action
What are the disadvantages of Glycopeptides?
They are excreted via the kidneys which, in kidney failure, can build up and increase damage
They only work on gram +ve cell walls
What are some examples of glycopeptides?
Vancomycin (IV)
Teicoplanin (IV)
What are some examples of antibiotic classes that target protein synthesis?
Aminoglycosides
Tetracycline
Macrolides
Lincosamides
What is an example of an aminoglycosides?
Gentamicin
What are some examples of Tetracyclines?
Doxycycline
Minocycline
What is an example of a lincosamide?
Clindamycin
How do aminoglycosides (Gentamicin) work?
It binds to the 30S ribosome irreversibly, thus preventing the production of proteins
What are the risks of gentamicin use?
It is toxic and can cause damage to kidneys and VIIIth cranial nerve (Vestibulocochlear)
How do tetracyclines work?
They are actively transported into the cell and bind to the 30S subunit, preventing attachment of tRNA to acceptor sites
What are the risks of tetracycline?
They can destroy the normal gut flora, resulting in increased risk of secondary infection. It also causes staining and impairment of bones and teeth
What are examples of macrolides?
Erythromycin
Clarythromycin
Azithromycin
How are macrolides excreted?
They are excreted into the liver, into the biliary tract and then into the gut
What are examples of antibiotics that affect nucleic acids?
Metronidazole
Trimethoprim
Fluoroquinolones
What are the uses of metronidazole?
Useful against anaerobes and parasites
How does metronidazole work?
It is activated by reduction, requiring intracellular low Eh. This forms a toxic intermediate that induces DNA strand breakage
How do Quinolones work?
They bind to the A subunit of DNA gyrase (topoisomerase) and prevent supercoiling of DNA, indirectly inhibiting DNA synthesis
What are examples of quinolones?
Ciprofloxacin
Nalidixic acid
What are examples of fluoroquinolones?
Ciprofloxacin
Levofloxacin
What antibiotics target folic acid synthesis?
Sulphonamides
Trimethoprim
What are the uses of trimethoprim?
Useful against some gram +ve and -ve bacteria
Commonly used for UTIs e.g. E.coli
What are the 3 most common side effects of antibiotics?
Nausea, vomiting and diarrhoea
What drugs classes action may be disrupted by antibiotics?
Oral contraceptives
What is a side effect of ciprofloxacin?
Tendonitis
What substance should not be taken with metronidazole?
Alcohol
What are the 4 Cs that can increase risk of Clostridium difficile?
Ciprofloxacin
Clindamycin
Cephalosporins
Co-amoxiclav
What disease is caused by the fungus Candida albicans?
Thrush
