Antibiotics 2 Flashcards
What are the 4 physiological mechanisms that antibiotics tend to target? [4]
- Cell wall biosynthesis
- Protein biosynthesis
- DNA and RNA replication
- Folate metabolism
Name 3 protein synthesis inhibitors that target the 50S ribosomal subunit [3]
- Macrolides
- Clindamycin
- Chloramphenicol
Name the 3 types of macrolides [3]
- Erythromycin
- Clarithromycin
- Azithromycin
Name 2 protein synthesis inhibitors that target the 30S ribosomal subunit [2]
- aminoglycosides
- tertracyclines
Give an example of an aminoglycoside antibiotic [1]
gentamicin
Give an example of a tetracycline antibiotic [1]
doxycycline
What are the bacteria that macrolides (in particular clarithromycin) are effective at targeting (incl. which class each bacteria is in)? [10]
- gram +ves
- streptococcus
- staphylococcus
- enterococcus
- respiratory gram -ves
- neisseria
- haemophilus
- atypicals
- legionella
- mycoplasma
- coxiella
- chlamydia
- chlamydophila
What are the potential adverse effects of macrolides (in particular clarithromycin)? [4]
- diarrhoea
- vomiting
- QT prolongation
- hearing loss with long-term use
Why is clarithromycin so susceptible to drug interactions? [1]
it is a potent inhibitor of cytochrome P450 enzymes
Which 3 drugs in particular should you avoid prescribing alongside clarithromycin? [3]
- simvastatin
- atorvastatin
- warfarin
Which bacteria is clindamycin effective at targeting (incl. which class each bacteria is in)? [4]
- gram +ve
- streptococcus
- staphylococcus
- (not enterococcus)
- anaerobes
- bacteroides
What are the 4 C. differgic antibiotics? [4]
- clindamycin
- co-amoxiclav
- cephalosporins
- ciprofloxacin
Chloramphenicol has an excellent broad spectrum of activity, but it is very toxic. What are the potential complications? [3]
- bone marrow suppression
- aplastic anaemia
- optic neuritis
Describe the mechanism of action of the aminoglycoside gentamicin [2]
- reversibly binds to the 30S ribosome
- bacteriostatic action
What are the potential toxic complications of gentamicin? [7]
- nephrotoxicity
- ototoxicity
- hearing loss
- loss of balance
- oscillopsia (severe problem with vision)
- neuromuscular blockade
- usually only significant in myasthenia gravis
Which bacteria is gentamcin effective at targeting (incl. which class each bacteria is in)? [7]
- gram -ve
- E. coli
- other coliforms
- neisseria
- haemophilus
- pseudomonas
- gram +ve
- staphylococcus
- streptococcus
- (not enterococcus)
Why should you avoid giving tetracyclines (like doxycycline) to children and pregnant women? [2]
- risk of bone abnormalities and
- tooth discolouration
Which bacteria is doxycycline effective at targeting (incl. which class each bacteria is in)? [10]
- gram +ve
- streptococcus
- staphylococcus
- enterococcus
- gram -ve
- neisseria
- haemophilus
- atypicals
- rickettsia
- mycoplasma
- coxiella
- chlamydia
- chlamydophila
Name 2 antibiotics that target DNA repair and replication [2]
- quinolones
- rifampicin
Name the 2 types of quinolones [2]
- ciprofloxacin
- levofloxacin
Which bacteria is the quinolone ciprofloxacin effective at targeting (incl. which class each bacteria is in)? [12]
- gram -ve
- pseudomonas
- haemophilus
- neisseria
- E. coli
- other coliforms
- gram +ve (less effective)
- streptococcus
- staphylococcus
- atypicals
- legionella
- mycoplasma
- coxiella
- chlamydia
- chlamydophila
What conditions is ciprofloxacin used to treat? [2]
- UTIs
- abdominal infections
Which conditions is levofloxacin used to treat? [1]
respiratory tract infections (due to stronger gram +ve activity than ciprofloxacin)
What are the potential toxic complications of levofloxacin? [3]
- gastrointestinal toxicity
- QT prolongation
- tendonitis
What conditions is rifampicin used to treat? [2]
- TB (in combination therapy)
- serious gram +ve infection (in combination therapy)
What does a typical TB lesion look like and where is it usually found? [3]
- epithelioid granuloma with central caseation necrosis
- most common site = alveolar macrophages in subpleural regions of the lung
Why is TB difficult to treat? [3]
- in order to reach their targets in intracellular bacilli, anti-TB drugs must overcome several barriers to enter a TB lesion, the most problematic of these is reduced vascularisation
- TB lesions also have dense bacterial populations (high bacterial burden)
- these bacteria tend to be slow growing which can influence the permeability of the pathogen to small drug molecules
How is the treatment of TB tailored to maximise efficacy? [2]
- prolonged courses of treatment (usually 6 months)
- use combination therapy (to prevent resistance and kill both growing and resting organisms)
What are the 4 drugs used to treat TB and describe the effect of each? [8]
- rifampicin
- bactericidial against slowly replicating organisms in necrotic areas
- isoniazid
- bactericidal against fast growing mycobacteria
- pyrazinamide
- bactericidal against slowly growing mycobacteria intracellularly
- ethambutol
- bacteriostatic against slow growing mycobacteria
What does inhibition of the folate metabolism pathway lead to? [2]
- impaired nucleotide synthesis
- therefore impaired DNA replication
Name the 2 antibiotics that inhibit folate synthesis [2]
- trimethoprim
- co-trimoxazole (combination of trimethoprim and sulphamethoxazole)
How is trimethoprim administered? [1]
orally
Which classes of bacteria is trimethoprim effective at targeting? [2]
- gram +ve
- gram -ve
What are the potential toxic complications of trimethoprim? [4]
- elevation of serum creatinine
- elevation of serum K+
- problematic in patients with chronic renal impairment
- rash
- GI disturbance
What are the potential toxic complications of co-trimoxazole? [2]
- bone marrow suppression
- Stevens Johnson syndrome (rare, severe condition affecting skin & mucous membranes)
What antibiotic is used to treat an uncomplicated UTI? [1]
trimethoprim
What antibiotic is used to treat a complicated UTI? [1]
ciprofloxacin
What antibiotics are used to treat someone severely unwell with UTI? [2]
- amoxicillin
- gentamicin
What antibiotics are considered safe for use during pregnancy? [3]
- most beta-lactams
- macrolides
- anti-tuberculants
What antibiotics are considered unsafe for use during pregnancy and why? [10]
- tetracyclines
- bone/tooth abnormalities
- trimethoprim
- neural tube defects (1st trimester)
- nitrofurantoin
- haemolytic anaemia (3rd trimester)
- aminoglycosides
- ototoxicity (2nd/3rd trimester)
- quinolones
- bone/joint abnormalities
