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
How do lower rates of Enterohepatic Recycling affect oral contraceptive effectiveness?
How do oral ABs play a role in this?
- Lower EHR rates-> Lower blood concentrations of Oestrogen/ Progesterone-> Increased risk of getting pregnant
- Oral ABs reduce gut flora-> Lowered EHR rates
