Antimicrobial Therapy Flashcards
What are the principles of prescribing antimicrobial therapy? (7 points)
- indications
- making a clinical diagnosis (type of infection, severity)
- patient characteristics
- antimicrobial selection
- regimen selection
- liaison with lab (causative organism)
- antimicrobial stewardship
What are the indication for antimicrobials?
Based on microbiology results
Prophylaxis:
Primary: antimalarial, immunosuppressed, pre-op, post-exposure (e.g. HIV)
Secondary: to prevent a second episode
How is diagnosis and severity assessed?
Clinical, lab based diagnosis
Severity: e.g. sepsis assessed by qSOFA
What patient characteristics are considered when prescribing antimicrobials?
Age Renal and liver function Immunocompromised Pregnancy Known allergies
What factors are considered for antimicrobial selection?
Individualised therapy: Likely organism(s) Empirical therapy (without microbiology results) or result based Bactericidal vs. bacteriostatic drug Single agent vs. combination Potential adverse effects
What are the common causative bacteria in soft tissue infections?
Strep. pyogenes Staph aureus Strep group C or G E. Coli Pseudomonas
What are the common causative bacteria in pneumonia?
Streptococcus pneumonia
Haemophilus influenzae
Staphylococcus aureus
Klebsiella pneumonia
What are the considerations for single vs. combination therapy?
Single: simpler, fewer side effects, fewer drug interactions
Combination: HIV and TB therapy, severe sepsis, mixed organisms
What is the regimen selection?
Route of administration, dose, adverse effects, duration, IV to oral switch therapy, inpatient or outpatient therapy
Therapeutic drug monitoring is important
What are the factors to decide IV or oral antimicrobial administration?
Oral route only if they are not vomiting, no shock, no organ dysfunction and normal GI function
IV route for severe or deep infection and when oral route is not reliable
What is the different between bactericidal or bacteriostatic?
Bactericidal: act on well wall, kill organisms, indications e.g. meningitis, endocarditis
Bacteriostatic: inhibit protein synthesis, prevent colony growth, require host immune system to ‘mop up’ residual infection, useful in toxin-mediated illness
What are the types of adverse effects from microbial therapy?
Immediate hypersensitivity: anaphylactic shock
Delayed hypersensitivity: rash, drug fever, serum sickness, erythema nodosum
What are the types of adverse effects relating to specific systems?
GI: nausea, vomiting, diarrhoea due to C. diff infection
Candida (thrush)- caused by broad spectrum penicillins
Liver SE- esp caused by tetracyclines, TB drugs
Renal SE: gentamicin, vancomycin
Neurological:
Ototoxicity- gentamicin, vancomycin
Optic neuropathy- TB drug
Convulsions, encephalopathy- penicillins, cephalosporin
Peripheral neuropathy- isoniazid (TB), metronidazole
Haematological- marrow toxicity
+ anaemia caused by cotrimoxazole
What communication occurs with the laboratory during microbial infections?
Send culture/ serology
Receive results- sensitivity results
Monitoring- disease activity, therapeutic drug monitoring
What are the principles of antimicrobial stewardship?
Follow antimicrobial guidelines
Audit of quality of antimicrobial prescribing
Education
What are the 4 C’s associated with clostridium difficile infection?
What is the importance of them?
Ceftriaxone
Co-amoxiclav
Clindamycin
Ciprofloxacin
Outbreaks of C. diff due to overuse of broad spectrum Abx, therefore use needs restricted
What are some classes of antibiotic therapy?
B-lactams (penicillins + cephalosporins) Aminglycosides Macrolides Quinolones Glycopeptides
What are the mechanisms of action of antibiotics?
Inhibition of cell wall synthesis= B lactams and Glycopeptides
Inhibiting protein synthesis within cell= akinglycosides, macrocodes, tetracyclines
Inhibition of nuclei acid synthesis= trimethoprim, sulphonamides, quinolones
Give examples of penicillins and examples of their main uses
Benzylpenicillin= soft tissue infection, pneumococcal, meningococcal
Amoxicillin= UTI, RTI
Flucloxacillin= Staph. aureus
Co-amoxiclav= UTI, RTI, soft tissue infection, surgical wound infections. (note= C. diff risk)
Give examples of Cephalosporins and examples of their main uses
Cefradine (1st generation)= UTI, soft tissue (note= resistance issue)
Cefuroxime (2nd)= UTI, RTI, surgical PPx
Ceftriaxone= HAI (note= MRSA + C. diff risk)
Give example of an Aminoglycoside and examples of its main uses
Gentamicin= serious gram negative infections
Need to measure therapeutic levels: renal + ototoxicity
Give examples of Macrolides and examples of their main uses
Clarithromycin= resp infection, soft tissue, STD
Erythromycin= as above
Azithromycin= chlamydia
Give examples of Quinolones and examples of their main uses
Ciprofloxacin= complicated UTI, complicated HA pneumonia, some GI infections (note= C. diff risk + may affect growing cartilage)
Levofloxacin= 2nd/3rd line agent for pneumonia
(side effects same as above)
Give an examples of a Glycopeptide and examples of its main uses
Vancomycin= MRSA, patients allergic to penicillin, C. diff infection (give oral vancomycin)
regular therapeutic monitoring due to nephrotoxicity
Study the other specific Abx examples on word document
e.g. trimethoprim co-trimoxazole clindamycin Doxycycline/ tetracycline Rifampicin Metronidazole Linezolid
What are the types of anti fungal drugs + their uses?
Azoles= candida + aspergillus
(e.g. Fluconazole)
Polyenes= candida + aspergillus
(e.g. Amphotericin)
Echinocandins= candida + aspergillus
Terbinafine= tinea, nails
Describe how antivirals work
They target several stages of virus life cycle (mainly intracellular stages)
Most are nucleoside analogues (inhibit nucleic acid synthesis)
They do NOT eradicate virus from latently infected cells, e.g. herpes viruses, so after treatment of overt infection, suppressive treatment may be needed
What types of antiviral treatments are there?
Prophylaxis
Pre-emptive (before symtpoms)
Overt disease (symptomatic)
Suppressive therapy (to limit viral replication)
Give examples of antivirals in practice (what they are used for)
Aciclovir= HSV 1+2, VZV, CMV
Interferon/Ribavirin= Hep B+C
Oseltamivir, Zanamivir= influenza, RSV
What cells do aciclovir drugs work on?
Aciclovir-like drugs are only active in herpes infected cell so that there is a low toxicity for uninfected cells
All antivirals have significant toxicity. Therefore what examples should they be used in?
Only in life or sight-threatening infections
e.g. HIV patients: CMV retinitis, colitis
Transplant patients: pneumonitis
What antiviral therapy is used for HIV?
Combination anti-retroviral therapy (cART)
What antivirals are used for Hepatitis B + C?
Hep B= Pegylated interferon alpha, nucleoside analogues
Hep C= Pegylated interferon alpha + protease inhibitor
