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
How would you manage this and why?
Concern re periorbital cellulitis
- Needs admission for IV antibiotics
- Check full range of eye movement, look for proptosis and ensure check visual acuity
- Consider possibility of development of orbital cellulitis → If concerns then may need CT/MRI
A 45 year old smoker presents with a one week history of cough, productive of green sputum. He reports getting bronchitis every year and antibiotics ‘always help’. His temperature is 37.8C. His PEFR in in normal range. On examination he has a few, occasional, transient, scattered coarse crepitations and mild wheeze, good air entry and vesicular breath sounds throughout. There are no focal or fine crepitations.
How would you manage this patient?
- Exclude pneumonia as a likely diagnosis → hx and examination
*>90% of cases of acute bronchitis do not have a bacterial cause
*Purulent sputum is not a predictor of bacterial infection
- Provide patient information leaflet explaining the limitations of antibiotics for this indication
- In this case a no or backup antibiotic prescription strategy with safety netting advice using a patient leaflet should be used → the symptoms do not suggest immediate antibiotic use is required.
NICE guidance – no antibiotic / delayed antibiotic if acute cough/bronchitis.
- Advise patients that resolution of symptoms can take up to 3 weeks
- Patients should be advised to seek a clinical review if condition worsens or becomes prolonged
Factors that indicate antibiotic treatment/further Ix for acute cough
Consider immediate antibiotics or further investigation/management for patients who are
- Systemically unwell
- Sympts or signs of serious illness e.g. pneumonia
- High risk of serious complications because of pre-existing co-morbidity
- >65 yrs + acute cough + 2 or more of the following OR >80 yrs +cough + 1 or more
- Hospitalization in past 12/12
- T1DM / T2DM
- Hx of CCF
- Current use of oral glucocorticoids
Patient with presumed bronchitis and no Abx treatment returns to the GP 2 weeks later. His symptoms have failed to improve. He continues to cough green sputum. He denies haemoptysis or weight loss. On examination his temperature is 38.2c, pulse 88 bpm regular, respiratory rate 18. He has left basal crepitations on examination.
How would you manage this patient now?
- If low risk CRB-65= 0
Amoxycillin 500mg pd tds for 5/7
OR clarithromycin 500mg po bd 5/7 or doxycycline 200mg stat the 100mg od 5/7 in total if pen allergy
- If intermediate risk CRB-65 = 1 and at home
Amoxycillin 500 mg pot ds 7/7 AND Clarithromycin 500mg po bd 7/7 OR doxycycline 200mg po stat then 100mg od for 7/7 in total
What factors would you consider when deciding whether to treat a patient with pneumonia in the community?
CRB-65 score
Confusion (recent). Respiratory rate >30/min. BP systolic <90 or diastolic <60. Age >65
Patients are stratified for risk of death as follows
- 0 : low risk <1% mortiality. Rx at home
- 1 -2 : intermediate risk (1-10% mortality risk). Hospital assessment or admission
- 3 – 4 : >10%, urgent hospital admission
Pt with pneumonia who received Abx treatment returns to see his GP 3 weeks later. He is feeling better in himself but his cough persists.
What would be your next course of action?
CXR
