Infections and antibiotics (1) Flashcards
B-lactams
- characteristic feature
- examples
- MoA
Beta-lactams
Characteristic: all contain beta-lactam ring
Examples: Penicillins such as amoxicillin and flucloxacillin; Cephalosporins such as cefalexin
MoA: Inhibit bacteria cell wall biosynthesis
Aminoglycosides
- characteristic feature
- examples
- MoA
Aminoglycosides
Characteristic: all contain aminosugar sunstructures
Examples: streptomycin, neomycin, kanamycin, paromomycin
MoA: Inhibit the synthesis of proteins by bacteria, leading to cell death
Chloramphenicol
- characteristic feature
- MoA
Chloramphenicol
Characteristic: chloramphenicol is a distinct individual compound; it’s commonly used in low-income countries
MoA: Inhibit synthesis of proteins, preventing growth.
*No longer a first line drug in any developed nation due to increased resistance and worries about safety.
Glycopeptides
- characteristics
- examples
- MoA
Glycopeptides
*drugs of last resort
Characteristics: consist of carbohydrate linked to a peptide formed of amino acids
Examples: Vancomycin, teicoplanin
MoA: Inhibit bacteria cell wall biosynthesis
Ansamycins
- characteristics
- examples
- MoA
Ansamycins
Characteristics: all contain an aromatic ring bridged by an aliphatic chain; can also exhibit anti-viral activity
Examples: Geldanamycin, rifamycin, naphthomycin
MoA: Inhibit the synthesis of RNA by bacteria, leading to cell death.
Streptogramins
- characteristics
- examples
- MoA
Streptogramins
Characteristics: Combination of two groups of antibiotics that act synergistically; two structurally differing compounds, from groups denoted A & B T
Examples: Pristinamycin IIA, Pristinamycin IA
MoA: Inhibit the synthesis of proteins by bacteria, leading to cell death.
Sulfonamides
- characteristics
- examples
- MoA
Sulfonamides
(first commercial antibiotic)
Characteristic: all contain sulfonamide group
Examples: Prontosil, sulfanilamide, sulfadiazine, sulfisoxazole
MoA: do not kill bacteria but prevent their growth and multiplication.
*Cause allergic reactions in some patients.
Tetracyclines
- characteristics
- examples
- MoA
Tetracyclines
Characteristics: all contain 4 adjacent hydrocarbon rings
Examples: Tetracycline, doxycycline, limecycline, oxytetracycline
MoA: Inhibit synthesis of proteins by bacteria, preventing growth
*use becomes less popular due to developing resistance
Macrolides
- characteristics
- examples
- MoA
Macrolides
Characteristics: all contain macrolide ring
Examples: Erythromycin, clarithromycin, azithromycin
MoA: Inhibit protein synthesis by bacteria, occasionally leading to cell death
Oxazolidinones
- characteristics
- examples
- MoA
Oxazolidinones
Characteristics: all contain 2-oxazolidone somewhere in their structure
Examples: Linezolid, posizolid, tedizolid, cycloserine. MoA: Inhibit synthesis of proteins by bacteria, preventing growth.
*very potent antibiotics, often used as ‘last resort’
Quinolones
- characteristics
- examples
- MoA
Quinolones
Characteristics: all contain fused aromatic ring with a carboxylic acid group attached
Examples: Ciprofloxacin, levofloxacin, trovafloxacin. MoA: Interfere with bacteria DNA replication and transcription.
Lipopeptides
- characteristics
- examples
- MoA
Lipopeptides
Characteristics: all contain lipid bounded to peptide
Examples: Daptomycin, surfactin
MoA: Disrupt multiple cell membrane functions, leading to cell death.
A 24 year old girl presents with a sore throat for the past 5 days – examination of her throat is shown on the picture.
What other information would you like to know that would aid in your decision to prescribe antibiotics?
Centor criteria:
- tonsillar exudates
- tender anterior cervical lymphadenopathy
- absence of cough
- history of fever >38C
If 3 or more of the criteria are present there is a 40-60% chance the sore throat is caused by Group A beta-haemolytic Streptococcus
Recommendation to treat if 3-4/4.
Absence of ¾ has NPV of 80%
Also if at risk of immunosuppression – chemotherapy, carbamazepine etc.
A 24-year-old girl presents with a sore throat for the past 5 days – examination of her throat is shown on the picture.
You decide to treat this lady with antibiotics – give the name, dose and duration of treatment? (two options if allergic to penicillin and if not)
- Penicillin V 500mg PO qds for 10 days
- Clarithromycin 500mg PO bd for 5 days
What other factors are important to consider when prescribing antibiotics for the bacterial throat infection? Any other advice?
- general advice re analgesia, fluids etc
- safety netting advice
- red flags for Quinsy
- complete the course of antibiotics
Do not use amoxicillin in case of EBV – can present in similar way.
Note – if unsure can consider delayed script
A 3 year old boy presents with his mother – he has been unwell for 2 days – off his food, and irritable. He has had no other symptoms other than pulling at his ear. On examination he is alert, temp 37.3C, pulse 100 bpm reg, RR 18/min, chest clear, few cervical lymph nodes and ear exam (on the picture).
What does the ear examination show?
- R ear – AOM
- L ear – Grommet
A 3 year old boy presents with his mother – he has been unwell for 2 days – off his food, and irritable. He has had no other symptoms other than pulling at his ear. On examination he is alert, temp 37.3C, pulse 100 bpm reg, RR 18/min, chest clear, few cervical lymph nodes and ear exam (on the picture).
How would you manage this boy?
- Analgesia – paracetamol and ibuprofen
- Delay antibiotic prescription for further 24 hours (total 72 hours) as likely to resolve itself (child is not unwell, no vomiting and no fever). *80% of cases will resolve in 72 hours with analgesia.
Could consider delayed script for amoxicillin for 5 days (if pen allergic – clarithromycin)
Consider immediate antibiotics if - child <2 years with bilat acute otitis media or child with otitis media + ottorrhoea
Indications for immediate antibiotic prescription in Acute Otitis Media
Antibiotics should be prescribed immediately if:
- Symptoms lasting more than 4 days or not improving
- Systemically unwell but not requiring admission
- Immunocompromise or high risk of complications secondary to significant heart, lung, kidney, liver, or neuromuscular disease
- Younger than 2 years with bilateral otitis media
- Otitis media with perforation and/or discharge in the canal
If an antibiotic is given, a 5-day course of amoxicillin is first-line.
In patients with penicillin allergy, erythromycin or clarithromycin should be given.
Would your management of Acute Otitis Media change if the right ear was discharging pus?
Yes
- immediate antibiotics and take swab → likely perforation
- review in 2 weeks → sooner if not improving after 2-3 days on antibiotics
Name 1 acute and 1 chronic complication that could arise during/following Acute Otitis Media?
- Mastoiditis
- Chronic supportative otitis media (glue ear)
A 3 year old girl presents with a 4 day history of a sticky right eye. On examination she had redness of her right conjunctiva with a purulent discharge. Her visual acuity and pupillary reflexes are normal.
How would you manage this child?
- Chloramphenicol 0.5% eye drops → 1 drop, 2 hourly during waking hrs for first 24hrs, thereafter qds. Treat for 48hrs after resolution
*topical fusidic acid is an alternative and should be used for pregnant women. Treatment is twice daily
- contact lens should not be worn during an episode of conjunctivitis
- advice should be given not to share towels
- school exclusion is not necessary
In uncomplicated conjunctivitis, do you always need to prescribe antibiotics immediately?
No. Large RCT trial in Lancet 2005 – cure rates identical at 1/52.
- Therefore generally keep clean and delayed prescription if not improving
- Generally advise good hygiene and cleaning measures for first 72 hours
- If not improving by 72 hours - consider antibiotic treatment / delayed script
How would you manage conjunctivitis in neonate?
- For neonatal conjunctivitis, treatment is often not indicated
- Advise cleaning only and take a swab for chlamydia and gonorrhoea
