Antibiotics Flashcards
(40 cards)
1
Q
What are the causes of infection?
A
- Bacteria
- Fungi
- Viruses
- Parasites
2
Q
What is bacteria and give some examples of some bacteria
A
- Single celled organisms with phospholipid bilayer membranes
- Only a tiny subset infect humans e.g.
- Staphylococcus aureus
- Escherichia coli
- Streptococcus pneumoniae
- Campylobacter jejuni
- Mycobacterium tuberculosis
- Yersinia pestis
3
Q
What is fungi and give some examples
A
- Fungi (type of eukaryote): Usually divided into moulds vs yeasts
- no peptidoglycan cell wall
- ribosomes are less distinct from our own
- more difficult to find drug targets
- Only a subset infect humans, eg:
- Candida sp.
- Aspergillus sp.
- Dermatophytes eg Trichophyton interdigitale
4
Q
What is a virus and give some examples
A
- Viruses: Replicate inside living cells of a cellular organism
- Hence, difficult to target them selectively (thus, supportive management and prevention → important)
- All cellular organisms have viruses, including Archaea and Bacteria
- Only a subset infect humans, eg:
- SARS-2 coronavirus
- Influenza virus
- Measles virus
- HIV, EBV, CMV, hepatitis viruses
Not included in the three-domain system because non-cellular!
5
Q
What is a parasite and give some examples
A
- Parasites: Loose term covering various not-closely-related, multicellular organisms eg
- Protozoa: Plasmodium malariae, Trypanosoma brucei, amoebae
- Helminths: tapeworms, flatworms, roundworms
- ‘Ectoparasites’: lice, mites, fleas
6
Q
What is the difference between antibiotics and antiseptics?
A
- Antibiotics: Broadly, drugs that kill* pathogens *without killing people
- Overlap between antibiotics and antiseptics, but essentially antibiotics bind to specific targets while antiseptics act more generally
Antibiotic: technically a naturally-occurring rather than a man-made antimicrobial but in practice the terms are synonymous
7
Q
What exceptions are there to drugs that work on more than 1 group?
A
-
Exceptions:
- Metronidazole active against flagellate parasites (‘Flagyl’) and strictly anaerobic bacteria
- Co-trimoxazole active against bacteria and Pneumocystis jirovecii
8
Q
How can we use antibiotics?
A
-
Treatment of infection
- Curative – ‘course’ of varying length
- Suppressive – often indefinitely
-
Prevention of infection
-
Before the infective event:
- prophylaxis – usually single dose
- eg operative prophylaxis
-
After the infective event:
- technically ‘pre-emptive therapy’ – single dose or short course
- eg meningococcal contact ‘prophylaxis’, bite injuries
-
Before the infective event:
-
Empiric therapy
- ‘Best guess’
- eg co-amoxiclav +/- gentamicin for suspected urosepsis
-
Targeted therapy
- Directed against a specific organism
- eg blood cultures growing E. coli susceptible to amoxicillin
9
Q
What are the major groups of antibacterials?
A
- Beta-lactams
- penicillins (amoxicillin, flucloxacillin) → end in -cillin
- cephalosporins (cefalexin,cefuroxime) → start with cef-
- (monobactams → aztreonam)
- carbapenems (imipenem, meropenem)
- Macrolides/azalides/lincosamides
- Tetracyclines (end in -cycline)
- Aminoglycosides
- Quinolones
- Glycopeptides
- Others:
- trimethoprim (UTI), nitrofurantoin (UTI), fosfomycin (UTI), colistin/colomycin (last resort for Gram -ve), chloramphenicol (eyes), linezolid (allergies OR MRSA infections), metronidazole (against strict anaerobes), rifampicin (TB)
10
Q
What do most antibacterials target?
A
- Target one of:
- Cell wall (peptidoglycan)
- Protein synthesis (ribosomes)
- A few target:
- DNA replication
- cell membrane
- folate metabolism
- Generally (not always):
- Cell wall agents are bacteriocidal
- Ribosomal agents are bacteriostatic
11
Q
Draw a beta-lactam ring
A
12
Q
Explain how beta lactams work
A
- Beta-lactam ring binds irreversibly to the enzymes that manufacture the bacterial peptidoglycan cell wall (‘penicillin-binding proteins’)
- Cell can’t make peptidoglycan
- Cell dies
13
Q
Draw the anatomy of a bacterium
A
14
Q
What is this condition?
Likely pathogens causing it?
What is the treatment & the alternative treatment?
A
- Cellulitis
- Likely pathogens:
- Probably Streptococcus pyogenes
- Possibly another pyogenic streptococcus or Staphylococcus aureus
- Typical treatment:
- Flucloxacillin
- Alternatives:
- Ceftriaxone
- Clindamycin
- Linezolid
- Daptomycin
15
Q
Explain how glycoproteins work (& example → main role)
A
E.g. vancomycin → for treating C.difficile
- Cell wall activity:
- molecule binds growing peptidoglycan cross-links
- Only active against Gram positive organisms
16
Q
Explain how macrolides work (& example → main roles)
A
E.g. erythromycin, clarithromycin (usually alternative to penicillins e.g. legionella & chlamydia trachoma’s & atypical pneumonias)
- Bind to bacterial ribosomes
- prevent protein synthesis > stops cell growing/dividing
17
Q
What condition, pathogen, treatment would this patient have?
A
- Community-acquired pneumonia
- Likely pathogens:
- Streptococcus pneumoniae
- Haemophilus influenzae
- but could be Legionella etc
- Typical treatment:
- co-amoxiclav plus
- clarithromycin
18
Q
Explain how tetracyclines work and examples & main roles
A
e.g. tetracycline, doxycycline
- Bind to bacterial ribosomes
- prevent protein synthesis > stops cell growing/dividing
- Good for respiratory infections, skin conditions (acne)
19
Q
Explain how aminoglycoside work and give examples & main roles
A
e.g. gentamicin
- Given IV OR topically
- Bind to bacterial ribosomes
- Prevent protein synthesis > stops cell growing/dividing
Main roles
- Not often used in isolation these days, though could do for UTI
- Usually used in combination e.g.
- UTI OR neutropenic sepsis
- Streptococcal endocard itis
20
Q
Explain how quinolones work and examples & main roles
A
E.g. ciprofloxacin
How work
- Bind to topoisomerase IV / DNA gyrase–DNA complexes
- prevents DNA replication > stops cell growing/dividing
Main roles
- Increasingly restricted* by side effects generally used when *no other options
well absorbed PO
21
Q
What are some antifungal drugs?
A
- Imidazoles
- Triazoles
- Echinocandins
22
Q
What is this condition?
A
Thrush/Oral Candida
23
Q
What is this condition?
A
Ringworm
24
Q
Give examples of some antiviral drugs
A
- Aciclovir
- AZT for HIV
- Oseltamivir for influenza
- remdesivir for COVID-19
25
Give examples of ***antiparasitic*** drugs and what they are used for
* ***Mebendazole*** for *threadworms (in caecum → lay eggs then eggs into anus → causes itching bum → spread to others)*
* ***Permethrin*** or malathion for *head lice* and *scabies*
26
Why does **antibiotic resistance** happen?
* Pathogens are living things and *evolve* in *response* to selective pressure
* They become *resistant* to *antibiotics*!
* There are *fewer* and *fewer* new *antibiotics* coming to market
27
What is this condition?
* **Paronychia**
* With a *pustule*
28
What is the current treatment for **gonorrhoea**?
* **IM ceftriaxone**
29
What are the **mechanisms** of *acquired resistance*?
* **Bacterium destroys the antibiotic**
* beta-lactamases
* aminoglycoside modifying enzymes
* **Bacterium modifies its target**
* penicillin-binding proteins in PRP
* peptidoglycan structure in VRE
* ribosomal proteins in macrolide and tetracycline resistance
* **Bacterium shuts the door**
* reduced permeability eg ertapenem resistance in Klebsiella
* **Bacterium pushes it out**
* efflux pumps
30
Why is ***antimicrobial*** _resistance_ a bad thing?
1. Infections are ***_harder_*** to treat → need more *_toxic_*, more *expensive*, less convenient agents
2. Infections can be more ***severe***
1. delayed optimisation of treatment
2. *_virulence_* often linked to resistance
3. Infections can be more ***common***
1. failure of *prophylaxis*
2. *vicious circles* related to virulence and colonisation resistance
31
How can we **prevent** antibiotic resistance?
* *Global coalition (e.g. agriculture, new drugs)*
* *Demand: reduce antibiotic use (patient education → more in PRIMARY CARE, surveillance, restrictions)*
* *Supply: develop _new_ antibiotics*
32
What is **antibiotic stewardship**?
* Things we do to *_optimise_* the *treatment* of current patients *_without_* *compromising* the care of future patients
* Guidelines
* Better diagnostics
* Prescriber education
* Patient education
* Use antibiotics **LESS** *(only when needed → when addvised by microbiologist)*and use them **BETTER** (*using narrower spectrum antibiotics)*
33
Explain *C.diff* and what the approaches are to minimise it?
* ***Clostridioides difficile*** infection
* An *ecological side effect* of *antibiotic* use
***_Approaches_***
* Clean healthcare environment
* chlorine better than detergent
* Don’t give it to people
* wash your hands
* clean your equipment
* Isolate cases
* +/- carriers
* Antimicrobial stewardship
34
When to do if someone says they have an ***allergy*** to ***penicillin***?
* Don’t take this at face value, always explore:
* vomiting / diarrhoea / dyspepsia – intolerance *_not_* *allergy*
* *_rash_* – cephalosporins *probably ok*
* ***_anaphylaxis_*** – *_avoid_* all beta-lactams, use something else
* ***10***% of people think they are allergic to penicillin, only ***_1_***% really are
35
What to do when someone has a UTI?
* Manage ***symptomatically***
* take a sample, wait and give *targeted treatment*
* treat ***empirically***
* want to cover *E. coli* and other ‘coliforms’
* want something well absorbed PO
* want something *well tolerated* and preferably *cheap*:
* *nitrofurantoin*
* *trimethoprim*
* (refer to previous ***cultures***)
36
What are some **symptoms** of a UTI?
37
What to do when someone has **bronchitis**?
* Manage ***symptomatically***
* take a *sample*, wait and give *targeted* *treatment*
* treat ***empirically***
* want to cover *Haemophilus influenza, Streptococcus pneumonia and Moraxella catarrhalis*
* want something well absorbed PO
* want something *well tolerated* and preferably *cheap*:
* *doxycycline*
* *amoxicillin*
* *clarithromycin*
38
What to do if someone has a ***skin infection*** like this:
* Manage ***symptomatically***
* take a sample, wait and give targeted treatment
* treat ***empirically***
* want to cover *Staph aureus*, streptococci
* want something well absorbed PO
* want something *well tolerated* and preferably *cheap*
* *flucloxacillin*
* *doxycycline*
* *clarithromycin*
39
What to do if someone has **endocarditis**?
* Manage symptomatically (rare, will have *night sweats non-specific symptoms as bacteria from the valves breaks off and gets into the blood stream)*
* take a sample, wait and give targeted treatment
* treat ***empirically***
* want to cover alpha-haemolytic streptococci
* in some scenarios want to cover staphylococci and enterococci
* need something bacteriocidal and available IV
* high dose ***amoxicillin*** plus ***gentamicin***
* *vancomycin plus gentamicin*
40
What to do if someone has **bacterial meningitis**?
* Manage ***symptomatically***
* ***DO A LUMBAR FUNCTURE***
* take a sample, wait and give *targeted treatment*
* treat ***empirically***
* want to cover *Neisseria meningitidis*, *Streptococcus pneumoniae* +/- *Listeria monocytogenes (when pregnant/immunocompromised)*
* need something IV, which crosses BBB and bacteriodical
* typically *cefotaxime +/- amoxicillin*
