Antimicrobials Flashcards
List the 3 types of Antibiotic Resistance
- Multi-drug Resistant (MDR)
- Extensively-drug Resistant (XDR)
- Pan-drug Resistant (PDR)
How do the Beta-lactam antibiotics work?
List 3 types
- Interfere with the synthesis of the cell wall (peptidoglycan)
- Penicillins
- Cephalosporins
- Carbapenems
What is Beta-lactamase?
Name a Beta-lactamase resistant drug
- Enzyme used by some bacteria to break down Beta-lactam Antibiotics
- Flucloxacillin
Why is Clavulanic Acid added to Amoxicillin to produce Co-amoxiclav?
Clavulanic Acid is a Beta-lactamase Inhibitor
Thus inhibits bacterial action of Beta-lactamase
What kind of Antibiotics are;
- Cefalexin
- Ceftriaxone
- Cefuroxime
- Cefotaxime
Cephalosporins (a type of beta-lactams)
List 4 types of Antibiotic that interfere with Protein synthesis
- Tetracyclines (prevent tRNA binding to Ribosomes)
- Aminoglycosides
- Macrolides
- Nitrofurans
Tetracyclines can be used in treating Respiratory infections, Acne, Chlamydia and Lyme disease
Why shouldn’t they be given to Children <12, Pregnants and Breastfeeding women?
Cause staining of developing teeth
List 3 Macrolides
- Clarithromycin
- Erythromycin
- Azithromycin
List common features of Pencillins and Macrolides
- Individual sensitivity testing required
- Similar clinical applications (Macrolides are also active against aytpical respiratory organisms)
List 7 common clinical applications of Macrolides and Penicillins
- Bacterial Meningitis
- Bone/ Joint infections
- Skin/ Soft tissue infections
- Otitis Media
- Pneumonia
- UTIs
- STIs
Describe why Nitrofurantoin is one of the 1st line treatments for UTIs?
- Up to 50% of an oral dose of Nitrofurantoin is excreted in urine in an unchanged form
- Allows Nitrofurantoin to concentrate in urine, increasing its effectiveness in the bladder (compared to other tissue compartments)
How do Quinolones work?
Name 2
- Inhibit Topoisomerase II (Bacterial DNA Gyrase), the enzyme permits Transcription/ Replication
- Ciprofloxacin
- Levofloxacin
Quinolones often require individual sensitivity testing.
List their clinical applications and antimicrobial properties
- Complicated UTIs
- Gonorrhoea
- Pseudomonas aeruginosa cover
- Very good cover of Gram(-ve)s as well atypical organisms and Gram (+ve)s
List ADRs of Quinolones
- Tendinitis +/- rupture
- Aortic dissection (Aortic aneurysm bursts)
- CNS effects (E.g Convulsions)
Sulfonamides are a type of AB that interfere with Folate Synthesis/ Action.
State another AB agent that acts in the same way
How does it work?
- Trimethoprim
- Folate antagonist, reversibly inhibits Dihydrofolate Reductase (stronger affinity for Bacterial DHFR than human)
State the clinical application for Trimethoprim
List an ADR
- UTIs
- Teratogenic effects on fetus (so caution when prescribing to females of reproductive age)
Why must patients avoid drinking alcohol when using Metronidazole?
Has Disulfiram-like action
build up of Acetaldehyde so hangover effects
Why is Acyclovir predominantly activated in infected cells?
How does it work?
List 2 clinical applications
- The viral enzyme Thymidine Kinase is more effective at phosphorylating and thus activating it
- Fully phosphorylated form inhibits viral DNA Polymerase
- Herpes simplex infections (Genital herpes, Encephalitis)
- Varicella Zoster (Chicken Pox, Shingles)
Herpes Simplex Virus (HSV) has 2 serotypes.
Compare their presentations
HSV1: Mouth/ lips/ eye infections
HSV2: Genital infection
Describe the use of Acyclovir to treat Oral herpes (HSV1)
- Do NOT prescribe Topical Antivirals (limited evidence supporting use)
- NICE DOES NOT recommend routine prescription of Oral Antivirals for healthy people with Herpes Labialis
Describe the use of Acyclovir to treat Genital herpes (HSV2)
1st episode;
- Oral Acyclovir within 5 days of start of episode OR while new lesions forming
Recurrent episodes;
- Episodic Antiviral treatment (Attacks infrequent at <6/year)
- Suppressive Antiviral treatment (Attacks frequent/ causing psychological distress/ affecting social life)
How does Metronidazole affect Warfarin metabolism?
Inhibits CYP2C9-> Reduced metabolism of Warfarin so greater effect
Verpamil and Simvastatin are metabolised by CYP3A4.
How do Macrolides affect their levels?
Macrolides inhibit CYP3A4 so increased effect
Describe Enterohepatic Circulation/ Recycling
- Drugs absorbed in intestines and taken into hepatocytes
- Drug/ metabolites secreted into bile and returned to intestine where more drug is absorbed into circulation
