Antimicrobial Therapy Flashcards
What are the types of antimicrobials?
Antibacterials => bactericidal, bacteriostatic
Antifungals => yeasts, moulds
Antivirals
Antiparasitics => helminths, protozoa, parasiticides
What are the 3 non pharmacological methods of treating infection?
Symptomatic relief only
Surgery/drainage => remove dead tissue and pus, send samples to lab to confirm cause
Improve host immunity or reduce/avoid immunosuppression
What are the consequences of inappropriate prescribing
Risk of increasing antimicrobial resistance
Side effects
Using IV when PO is more appropriate => increased risk of infection, costs
Unecassery costs
When should you use antibiotics
Essential for
- limiting tissue spread, collateral damage
- high mortality infections
- shortening duration of pain, suffering
- reduce complications of uncontrolled infection
How would you manage these common overprescription problems?
- total course is too long
- too much given IV
- too broad spectrum
- misuse of prophylaxis
Total course is too long => specific indication and stop date
Too much given IV => switch to PO at earliest opportunity
Too broad spectrum => select narrow spectrum agents
Misuse of prophylaxis => surgical prophylaxis (only needed immediately before and after)
What are the causative organisms for these infections
- Gonorrhoea
- Syphilis
- Malaria
- Typhoid
- Lyme disease
- TB
Gonorrhoea => neisseria gonorrhoeae Syphilis => treponema pallidum Malaria => plasmodium species Typhoid => salmonella typhi Lyme disease => borrelia species TB => mycobacterium tuberculosis
How would we test for antimicrobial susceptibility
Disc testing => test for sensitivity or resistance against antibiotics
Minimum inhibitory concentration
-lowest concentration of antibiotic that inhibits growth
Minimum bactericidal concentration
-lowest concentration that kills
How would you choose the drugs for treatment
-considerations you must make
Sensitivity of likely causative organism
Will drug reach the site of infection
What route is the most appropriate
Side effects and adverse effects of combinations
Cost
What 3 drug classes are b lactams How do they work What types of bacteria do they work on? Excretion? Adverse reactions? Resistance?
G+ve, -ve, anaerobic
Penicillins
Cephalosporins
Carbapenems
Anti cellwall activity => bactericidal
Renal
Crossreactivity with cephalosporins and carbopenems
Beta lactamase resistance
Which penicilins are
- narrow spectrum
- broad spectrum
What 3 penicillins are PO and IV
Narrow
- Penicillin V (PO)
- Penicillin G (IV)
- Flucloxacillin (PO, IV)
Broad
- Tazocin (IV) => against pseudomonas aeruginosa)
- Amoxicillin, co-amoxiclav (PO, IV)
Which cephalosporins are
- narrow spectrum
- broad spectrum
What 2 cephalosporins are IV only
What cephalosporin is IV and PO
What risks are associated with cephalosporin use
Narrow
- Cefalexin (PO)
- Cefadroxil (PO)
Broad
- Ceftazidime (IV) => against pseudomonas aeruginosa)
- Ceftriaxone, cefotaxime (IV)
- Cefuroxime (PO and IV)
Use increases risk of C diff colonisation
Which 2 carbapenems are
-broad spectrum
Broad
- Ertapenem (IV)
- Meropenem (IV) => pseudomonas aeruginosa
How do macrolides work
- Gram?
- Excretion?
- Adverse reactions?
- Resistance?
- when would you use these
Name the 3 main macrolides
-which 2 have longer half lives and fewer SE
Binds to 50S ribosomal subunit => bacteriostatic
G+ve, -ve
- penicillin allergies
- vs staphylococci, streptococci (skin, throat infections)
- atypical pneumonias
Hepatic
GI side effects
- diarrhoea, nausea, vomiting, abdo pain
- hepatitis
Alter target sites
Erythromycin (IV, PO)
Have longer half lives and fewer SE
-Clarithromycin (IV, PO)
-Azithromycin (PO)
How do tetracyclines work
- Gram
- Excretion?
- Adverse reactions?
- Resistance?
- when would you use these
Name the 3 main tetracyclines
Bind to 30s ribosomal subunits => bacteriostatic
G+ve cocci, rods, atypicals
- used in penicillin allergies with macrolide SE
- resp tract, soft tissue infections
- acts on atypical respiratory pathogens
Renally, GI
Esophageal ulceration
Photosensitivity
Incoorporated into children’s teeth
Broad spectrum but prone to resistance
Doxycycline
Oxytetracycline
Tigecycline
How do trimethoprim and co-trimoxazole work
-when would you use each one
What are the side effects of sulphonamides
Block synthesis of bacterial nucleotides in G+ve, G-ve
Trimethoprim => UTIs (bacteriostatic in isolation)
Co-trimoxazole (trimethoprim + sulfamethoxazole) => PJP, nocardias (bacteriocidal in combination)
Sulphonamides (sulfamethoxazole)
- Steven Johnson syndrome
- BM suppresion, aplasia
How do quinolones work
- Gram?
- Excretion
- Adverse effects
- Resistance
- which 2 are better at handling G+ve
Bactericidal => inhibits DNA gyrase
G+ve, G-ve
Renal
CDiff risk
Quinolone cannot bind to mutated DNA gyrase
Ciprofloxacin
Respiratory quinolones (better G+ve cover)
-levofloxacin
-moxifloxacin
How do aminoglycosides work
- Gram?
- Main use
- Adverse effects
- Excretion
- Methods of resistance
Name the 4 main ones
Bactericidal => binds to 30S ribosomal unit in G-ve
G-ve septicemia, sepsis
Bacterial endocarditis
-synergistic with B lactams
- reversible nephrotoxic => intrinsic AKI
- permanenet ototoxic => VIII palsy
- NMJ blockade => paralysis
Renal
Inactivated by aminoglycoside modifying enzymes
Gentamicin
Amikacin
Neomycin
Tobramicin
How do glycopeptides work
- Gram
- Uses
- Excretion
- Adverse effects
- Resistance
What are the 2 main ones
Inhibit cellwall peptidoglycan synthesis
G+ve only
FIRST LINE FOR MRSA, CDiff
Renal
Nephrotoxic
Ototoxic
Vancomycin cannot bind to altered cell wall peptides
Vancomycin
Teicoplanin
Metronidazole
- what kind of microbes would be affected
- excretion
-Anerobes (trichomonas vaginalis), amoeba, protozoa
Destabilises bacterial DNA
Renal
What bacteria do these ABx work on
Linezolid
-what kind of microbes would be affected
Daptomycin
-what is it effective against
Rifampicin
- what is it effective against
- in what 2 situations would you use this
G+ve
Linezolid
- MRSA
- glycopeptide resistant entercocci (VRE)
Daptomycin
Rifampicin
- prosthetic infections
- TB regimen
Chloramphenicol
- when would you use it
- why is this not commonly used
Eye, ear infections
Life threatening haem influenza, typhoid infections
Bone marrow toxicity
Fosfomycin
-when would you use it
Colistin
-what is the only indication for its use
Fosfomycin
-multi resistant G-ve infections (UTIs)
Colistin
Last line for G-ve
Fidaxomicin
-what is the only indication for its use
Only for selected cases of severe/recurrent CDiff diarrhoea
Fusidic acid
- what is the only use
- when would you use this in combination
Staphylococcal infection only
-if systemic, use with another anti staph drug
Why do we have antibiotic resistant bacteria
Why do we face a massive problem
Rapid evolution via mutation
-DNA acquisition
ABx overuse
- patient’s expectations
- high dependency users
Lack of novel compounds
What are the 3 methods of acquiring resistance genes
Conjugation => sex pili used to transfer genetic material
Transformation => uptake of free DNA
Transduction => DNA transfer via bacteriophages
What are the 2 most common yeasts
- where would they cause infection
- in what situations would they cause infection
Candida albicans
Candida glabrata
Urinary tract
Intra abdo
Bloodstream
Immunocompromised due to
- Solid organ transplant
- Critical care environmnets
What moulds would you have to be aware of
- where would they cause infection
- in what environments would infection be likely
Aspergillus
Sinusitis
Pulmonary
Disseminated
Immunocompromised due to
- transplant
- haematooncology
What are the 3 groups of antifungals for systemic infections
-name some examples
Azoles
- fluconazole
- itraconazole
- voriconazole
- posaconazole
Echinocandins
- caspofungin
- anidulafungin
- micafungin
Polyenes
-amphotericin
