URTI Flashcards
Pharyngitis - Site of infection
Oropharynx, nasopharynx (i.e. sore throat)
Pharyngitis - Clinical presentation
1) Acute onset of sore throat
2) Fever
3) Pain when swallowing
4) Erythema & inflammation of pharynx & tonsils, with/without patchy exudates
5) Tender & swollen lymph nodes
Pharyngitis - Microbiology
1) Virus (> 80%)
- Rhinovirus, coronavirus, influenza, parainfluenza, Epstein-Barr
2) Bacteria (< 20%)
- No. 1 cause: Group A ß-hemolytic Streptococcus i.e. Streptococcus pyogenes (strep throat)
Pharyngitis - Prevalence of strep throat
US:
- Adults: 5 - 15%
- Children: 20 - 30%
SG:
- Less common
Pharyngitis - Pathogenesis
Transmitted via direct contact with droplets of infected saliva/nasal secretions
Short incubation: 24 - 48h
Causes acute inflammation at oropharynx & nasopharynx
Pharyngitis - Complications (viral pharyngitis)
Generally self-limiting
Recovers within a few days to weeks with rest & adequate hydration
Pharyngitis - Complications (strep throat)
May be self-limiting or complicated
Complications may occur 1 - 3 weeks later, after initial sore throat has gone away
- Due to initial infection triggering a systemic inflammatory response
Complications:
1) Acute rheumatic fever
- Fever due to severe inflammation caused by infection
- Prevented by early initiation of effective antibiotics –> should give antibiotics as soon as strep throat is diagnosed
2) Acute glomerulonephritis
- Low incidence
- NOT prevented by antibiotics
Pharyngitis - Differential diagnosis
Difficult to differentiate between viral VS bacterial pharyngitis, due to similar clinical presentation
Diagnose strep throat based on:
1) Diagnostic tests
2) Clinical diagnosis
- Frequently used for diagnosis
Pharyngitis - Diagnosis of strep throat
- Diagnostic tests
- Clinical diagnosis
Diagnostic tests:
1) Throat culture
- Advantages: Gold standard; High sensitivity (90 - 95%)
- Limitations: Takes time for cultures to grow (24 - 48h) –> delay initiation of Abx
- Clinical use: Not very useful
2) Rapid antigen detection test (RADT)
- Advantages: Very fast (within minutes)
- Limitations: Lower sensitivity (70 - 90%); Expensive
Clinical diagnosis:
1) Modified centor criteria
- Score given based on patient background & S/Sx
- Higher score –> higher risk of S. pyogenes pharyngitis
- Score used to make diagnosis / decide on need for antibiotics
- Score = 0, 1 - Presumed viral; No additional testing indicated
- Score = 2, 3 - Test for S. pyogenes pharyngitis (rarely done) OR Initiate empiric antibiotics (more common)
- Score = 4, 5 - Initiate empiric antibiotics
- Note: Children < 3 years - Presumed viral
Treatment of pharyngitis
1) Antibiotic treatment
- Indication: Strep throat
- Generally empiric
2) Supportive care
- Indication: Viral/Bacterial pharyngitis
3) Corticosteroids
- NOT recommended
Treatment of pharyngitis - Supportive care
Indicated for both bacterial & viral infection
1) Antipyretic / Analgesic - Paracetamol, NSAIDs
- Avoid Aspirin in children - Reye syndrome
2) Topical analgesic lozenges/sprays
- E.g. Benzydamine
3) Saltwater gargle
4) Adequate fluid & rest
Treatment of pharyngitis - Corticosteroids
Benefits
- Reduce duration & severity of symptoms by reducing inflammation
Limitations
- Associated with side effects
Overall: NOT recommended
Empiric antibiotic treatment of pharyngitis - Benefits
1) Prevent acute rheumatic fever
2) Shorten duration of symptoms by 1-2 days
3) Reduce transmission (no longer infectious after 24h of antibiotics)
Empiric antibiotic treatment of pharyngitis - Organisms to cover
S. pyogenes
Empiric antibiotic treatment of pharyngitis - Choice of antibiotics
1st Line:
1) Penicillin VK
- Most narrow, directed therapy
Alternative:
1) Amoxicillin OR Cephalexin
- Alternative in mild penicillin allergy
- Note: Amoxicillin alone is sufficient –> Augmentin is too broad spectrum
2) Clindamycin OR Clarithromycin
- Alternative in severe penicillin allergy
- Choice depends on patient preference, C/I
Empiric antibiotic treatment of pharyngitis - Dosing
Duration: 10 days
Adult Dosing:
Penicillin VK
- PO 250 mg QDS OR PO 500 mg BD
- Renal dose adjustment needed
Amoxicillin
- PO 1g OD OR PO 500 mg BD
- Renal dose adjustment needed
Clindamycin
- PO 300 mg TDS
Pediatric Dosing:
Penicillin VK
- PO 250 mg BD - TDS
- Renal dose adjustment needed
Amoxicillin
- PO 50 mg/kg/day OD or divided BD
- Renal dose adjustment needed
Clindamycin
- PO 7 mg/kg TDS
Pharyngitis - Monitoring
Therapeutic response
- Clinical improvement expected within 24-48h after initiation of antibiotics
- Resistance to antibiotics rare
Sinusitis - Site of infection
Paranasal & nasal mucosa
Sinusitis - Clinical presentation
Sinusitis:
- ≥ 2 major symptoms OR
- 1 major + ≥ 2 minor symptoms
Major symptoms
1) Purulent anterior nasal discharge
2) Purulent/Discoloured posterior nasal discharge
3) Nasal obstruction/congestion
4) Facial congestion/fullness
5) Facial pain/pressure
6) Hyposmia/Anosmia
7) Fever
Minor symptoms
1) Headache
2) Ear pain, pressure, fullness
3) Halitosis
4) Cough
5) Fatigue
6) Dental pain
Sinusitis - Microbiology
Viral (> 90%)
- Rhinovirus, adenovirus, influenza, parainfluenza
Bacteria (< 10%)
- Most common: Streptococcus pneumoniae, Haemophilus influenzae
- Others: Moraxella catarrhalis, Streptococcus pyogenes
Fungi
- Mainly occurs in immunocompromised patients
Sinusitis - Pathogenesis
Transmission: Direct contact with infected saliva / nasal secretions
Acute inflammation of paranasal & nasal mucosa –> sinus obstruction –> nasal mucosal secretions trapped in sinus cavities (accumulation) –> medium for bacterial trapping & multiplication
Bacterial sinusitis usually preceded by viral URTIs (e.g. common cold, pharyngitis) i.e. complication of viral URTIs
- Runny nose during viral URTIs –> sniff back mucus –> accumulation in sinus cavities –> medium for bacterial trapping & multiplication
Sinusitis - Differential diagnosis
Difficult to differentiate between bacterial VS viral sinusitis
- Similar clinical presentation
Diagnosis of bacterial sinusitis based on:
1) Diagnostic tests
- Limited use
2) Clinical diagnosis
- Frequently used
Sinusitis - Diagnosis of bacterial sinusitis
- Diagnostic tests
- Clinical diagnosis
Diagnostic tests
1) Imaging studies (e.g. CT scan)
- Limitation: Non-specific, non-discriminatory –> only tests for presence of inflammation but unable to differentiate between viral VS bacterial sinusitis
2) Sinus aspirate
- Gold standard
- Limitations: Painful, invasive, time-consuming
- Usually only used in immunocompromised patients –> may have polymicrobial infections / infected by organism other than bacteria/virus
Clinical diagnosis
Presence of sinusitis (≥ 2 major symptoms / 1 major + ≥ 2 minor symptoms)
AND
Any one of the following:
1) Persistent symptoms > 10 days AND no improvement
- Viral sinusitis is usually self-limiting & resolves within 7 - 10 days
2) Severe symptoms
- Purulent nasal discharge x 3 - 4 days OR
- High fever ≥ 39oC
3) Double worsening
- Worsening of symptoms 5 - 6 days after initial improvement
- Likely complicated by secondary bacterial infection
Treatment of sinusitis
1) Antibiotic treatment
- Indication: Bacterial sinusitis
- Generally empiric
2) Supportive care
- Indication: Viral/Bacterial sinusitis
Treatment of sinusitis - Supportive care
1) Antipyretic/Analgesic - NSAIDs, Paracetamol
- Avoid Aspirin in children
2) Nasal steroid spray
3) Saline irrigation
4) Expectorant - Guaifenesin
5) Nasal/Systemic decongestants/antihistamine
- NOT guideline recommended
Empiric antibiotic treatment of sinusitis - Benefits
1) Shorten duration of symptoms
2) Earlier symptom relief
3) Restore QOL
4) Prevent complications
Empiric antibiotic treatment of sinusitis - Organisms to cover
S. pneumoniae
H. influenzae
Empiric antibiotic treatment of sinusitis - Duration
Adults: 5 - 10 days
- Studies supporting shorter duration, with similar cure
- Improves compliance
- Minimize ADR due to antibiotics
Paediatric: 10 - 14 days
Empiric antibiotic treatment of sinusitis - Choice of antibiotics
1st Line:
1) Amoxicillin
2) Amoxicillin-Clavulanate
- Used if suspect ß-lactamase producing H. influenzae
- Use if any ONE of the following:
• Recent antibiotic use in past 30 days
• Recent hospitalization in past 30 days
• Failure to improve after 72h of Amoxicillin
Alternatives in penicillin allergy:
1) Respiratory fluoroquinolones - Moxifloxacin, Levofloxacin
2) Cotrimoxazole
3) Cefuroxime
- Mild penicillin allergy
Empiric antibiotic treatment of sinusitis - AVOID using
1) Ciprofloxacin
- Poor activity against S. pneumoniae
2) Macrolides, Tetracyclines
- High local resistance of S. pneumoniae to Macrolides & Tetracyclines
3) Penicillin VK
- Penicillin-resistant S. pneumoniae which requires high dose for effective treatment
- High dose Amoxicillin preferred over high dose Penicillin due to favourable PK (better bioavailability)
Empiric antibiotic treatment of sinusitis - Dosing
Adult Dosing:
Amoxicillin
- PO 1g TDS (high dose)
- Renal dose adjustment needed
Amoxicillin-Clavulanate
- PO 1g BD (high dose) OR
- PO 625 mg TDS
• High dose –> risk of GI effects –> increase dosing frequency instead
• Most public hospitals carry 625 mg Augmentin (more cost-effective, readily available, smaller tablet size)
- Renal dose adjustment needed
Levofloxacin
- PO 500 mg OD
- Renal dose adjustment needed
Paediatric Dosing:
Amoxicillin
- PO 80-90 mg/kg/day, divided BD (high dose)
Amoxicillin-Clavulanate
- PO 80-90 mg/kg/day, divided BD (high dose)
Levofloxacin
- C/I in children
Antibiotic resistance - S. pneumoniae
- MOA
- Prevalence
- Treatment
MOA
- Multi-step mutation of penicillin-binding proteins (PBP)
- Results in increased penicillin MIC with each mutation
Prevalence
- Penicillin-resistant isolates uncommon locally (< 5 - 10%)
- May not be completely resistant –> requires higher dose
Treatment
- High dose OR Increased frequency Amoxicillin
- Amoxicillin preferred over penicillin due to favourable PK –> higher bioavailability –> achieves higher systemic concentrations
Antibiotic resistance - H. influenzae
- MOA
- Prevalence
- Treatment
MOA
- Production of ß-lactamase –> breaks down ß-lactams
Prevalence
- ß-lactamase positive: ~18% locally
Treatment
- Amoxicillin-Clavulanate (use of ß-lactamase inhibitors)
AOM - Site of infection
Middle ear
AOM - Clinical presentation
1) Otalgia
2) Otorrhoea
3) Ear popping/fullness
4) Hearing impairment
5) Dizziness
6) Fever
Young children/infants may present with non-specific symptoms
- Ear rubbing
- Excessive crying
- Change in sleep/behavioural patterns
AOM - Risk factors
1) Children (especially < 5 years)
- Eustachian tube in children is flatter, more horizontal –> easier for nasal discharge to flow backwards
2) Siblings
3) Daycare
4) Supine position when feeding
5) Exposure to tobacco smoke
6) Pacifier use
7) Winter season
AOM - Pathogenesis
Generally occurs as a complication of viral URTI
During viral URTI
- Secretion & inflammation –> obstruction of Eustachian tube –> negative Eustachian tube pressure
- Nose sniffing
Overall: Results in reflux of secretions into middle ear –> accumulation of discharge/fluid in middle ear –> medium for bacterial accumulation & growth –> middle ear infection resulting in inflammation & fluid accumulation
AOM - Microbiology
1) Viral (40-45%)
- Respiratory syncytial virus (RSV), rhinovirus, adenovirus, parainfluenza
2) Bacteria (55-60%)
- Streptococcus pneumoniae
- Haemophilus influenzae
- Moraxella catarrhalis
AOM - Diagnosis
Diagnostic tool: Pneumatic otoscope
Diagnostic criteria in children:
1) Acute onset (< 48h)
2) Otalgia OR Erythema of tympanic membrane
- Rubbing, tugging, holding in non-verbal child
3) Bulging of tympanic membrane
- Usually due to fluid accumulation in middle ear
Note: Differential diagnosis (bacterial VS viral) difficult due to:
- Similar clinical presentation
- Similar prevalence
Treatment of AOM - Supportive care
1) Analgesic / Antipyretic - NSAIDs, Paracetamol
- Avoid Aspirin in children
Decongestants & antihistamines NOT shown to be beneficial
Empiric antibiotic treatment of AOM - Immediate initiation
1) How it works
2) Benefits
3) Limitations
How it works:
Start antibiotics at initial doctor’s visit
Benefits:
1) Prompt initiation of antibiotics decrease duration of symptoms by ~1 day
Limitations:
2) Risk of antibiotic overuse
Empiric antibiotic treatment of AOM - Observation period
1) How it works
2) Benefits
3) Limitations
How it works:
No antibiotics given at initial doctor’s visit
Supportive care x 48-72h
If fail to improve/worsens: Antibiotics initiated
Benefits:
1) Prevents overuse of antibiotics
- Difficult to differentiate between viral VS bacterial AOM
- Most bacterial AOM are self-limiting –> resolve within 3-4 days without antibiotics
Limitations
1) Inconvenient (may require 2nd doctor’s visit)
2) Requires reliable follow-up
- Must be able to monitor child at home
Empiric antibiotic treatment of AOM - Observation period criteria
May only be considered if ALL of the following are fulfilled:
1) ≥ 6 months
- Younger children at higher risk of complications/less likely to get better without antibiotics
- Older children better able to report symptoms
2) Non-severe illness
- Severe: Moderate-severe otalgia OR Otalgia ≥ 48h OR Fever ≥ 39oC
- Non-severe: Absence of ALL of the above
- Note: Assessing severity can be difficult –> severity of otalgia is subjective, difficult for younger patients to report symptoms
3) No otorrhoea
- Otorrhoea can indicate rupture of tympanic membrane
4) Possible for close-follow-up
5) Shared decision making with parent/caregiver
Empiric antibiotic treatment of AOM - When can observation period be considered
1) No otorrhoea AND
2) Unilateral AOM + ≥ 6 months OR Bilateral AOM + ≥ 2 years
Empiric antibiotic treatment of AOM - Watch & wait
1) How it works
2) Benefits
3) Use in SG
How it works:
Prescription given at initial doctor’s visit
Supportive care x 48h
Prescription only filled in after 48h if fails to improve/worsens
Benefits
1) Increased convenience
2) Parent satisfaction
3) Prevent overuse of antibiotics
- Only 2/3 of prescriptions filled –> most cases are self-limiting
Rarely used in SG
Empiric antibiotic treatment of AOM - Organisms to cover
1) S. pneumoniae
2) H. influenzae
3) Moraxella catarrhalis
Empiric antibiotic treatment of AOM - Duration
< 2 years: 10 days
Severe symptoms (moderate-severe otalgia OR otalgia ≥48h OR fever ≥ 39oC): 10 days
≥ 2 - 5 years AND non-severe: 7 days
≥ 6 years AND non-severe: 5 - 7 days
Empiric antibiotic treatment of AOM - Choice of antibiotics
1st Line: 1) Amoxicillin - Used if fulfil ALL of the following: • No Amoxicillin in past 30 days • No concurrent purulent conjunctivitis • Not allergic to penicillin
2) Amoxicillin-Clavulanate
- Used if ANY ONE of the following:
• Amoxicillin in past 30 days (suspect ß-lactamase producing H. influenzae)
• Concurrent purulent conjunctivitis (suspect MSSA)
• History of AOM non-responsive to Amoxicillin
Alternative
1) Ceftriaxone (IM) OR Cefuroxime
- Alternative in mild penicillin allergies
2) Clindamycin
- Alternative in severe penicillin allergies
- Note: Does NOT cover H. influenzae
3) Respiratory Fluoroquinolones
- Alternative in severe penicillin allergies
- For adults only; C/I in children
Empiric antibiotic treatment of AOM - Dosing
Paediatric Dosing:
1) Amoxicillin
- PO 80 - 90 mg/kg/day divided BD (high dose)
- Renal dose adjustment needed
2) Amoxicillin-Clavulanate
- PO 80 - 90 mg/kg/day divided BD
- Renal dose adjustment needed
3) Cefuroxime
- PO 30 mg/kg/day divided BD
- Renal dose adjustment needed
Non-pharmacological treatment of AOM - Prevention
1) Minimize exposure to tobacco smoke
2) Exclusive breastfeeding for first 6 months
3) Minimize pacifier use
4) Vaccinations
- Influenza
- Pneumococcal
- H. influenzae type B
AOM - Monitoring
Treatment response
- May worsen in first 24h
- Improvements expected after 48-72h
Treatment failure
- Initially Amoxicillin –> switch to Augmentin
- Initially Augmentin –> switch to Cefuroxime / Ceftriaxone
- Treatment failure is rare
Influenza - Clinical presentation
Incubation period: 24 - 72h
Abrupt onset
Signs & symptoms: Usual/Common: 1) Fever 2) Body aches 3) Chills 4) Fatigue, body weakness 5) Chest discomfort 6) Headache Less common: 1) Sneezing 2) Stuffy nose 3) Sore throat
Influenza - Differential diagnosis
1) VS Common cold
2) VS Covid-19
Common cold:
- Influenza: Abrupt onset VS Common cold: Gradual onset
- More common in influenza: Fever, chills, body ache, fatigue, body weakness, chest discomfort, headache
- More common in common cold: Sneezing, stuffy nose, sore throat
Covid-19:
- Similar symptoms: Fever, body aches, chills, fatigue/body weakness, stuffy/runny nose, sore throat, chest discomfort, headache
- Classical for Covid-19: Change in/Loss of taste/smell, N/V, diarrhea
Influenza - Epidemiology in SG
Bimodal distribution - Peaks in:
1) Dec - Feb
2) May - Jul
Influenza - Microbiology
1) Influenza A
- Host: Human, swine, equine, avian, other species
- Most severe illness
- Significant mortality in young persons
- Epidemics & pandemics
2) Influenza B
- Host: Human only
- Severe illness in elderly, high risk groups
- Less severe epidemics
3) Influenza C
- Host: Human, swine
- Mild illness
- No seasonality
- No epidemics
Influenza - Diagnosis
1) Viral cultures
- Not recommended –> takes long time to get results
2) Molecular tests
- Outpatient: Limited use; Diagnosis mainly based on symptoms; Usually empiric treatment
- Inpatient: May be used; RT-PCR
Influenza - Complications
1) Viral pneumonia
2) Post-infection bacterial pneumonia
- Especially those caused by S. aureus
- High mortality (> 30%)
- Can result in respiratory failure, organ damage
3) Respiratory failure
4) Exacerbation of cardiac/pulmonary comorbidities
5) Febrile seizures
6) Myocarditis, pericarditis
Influenza - High risk group
1) Children < 5 years
2) Elderly ≥ 65 years
3) Pregnant women / Within 2 weeks post-partum
4) Residents of nursing homes/long-term care facilities
5) Obesity (BMI ≥ 40 kg/m^2)
6) Chronic medical conditions
- Mainly pulmonary / cardiac conditions
- E.g. Asthma, COPD, heart failure, DM, chronic kidney disease, immunocompromised
Management of influenza
1) Prevention
- Chemoprophylaxis
- Non-pharmacological
- Vaccination
2) Antiviral treatment
Influenza - Non-pharmacological prevention
1) Good personal hygiene
- Wash hands
- Minimize touching eyes, nose, mouth
- Cover nose & mouth when coughing/sneezing
- Wear mask if unwell
- Use serving spoon if sharing food
2) Maintain healthy lifestyle
- Exercise regularly
- Adequate sleep
- Balanced diet
- Do not smoke
Influenza - Vaccination
1) Types of influenza vaccines
2) Administration
3) Indication
Types of influenza vaccines
- Inactivated trivalent / quadrivalent vaccine
Administration:
- Route: IM
- Administered yearly (only lasts for 1 year)
- Onset: ~2 weeks from administration
Indication:
ALL individuals ≥ 6 months, unless contraindicated
- Very few contraindications
Influenza - Types of chemoprophylaxis
1) Pre-exposure
2) Post-exposure
Influenza - Pre-exposure chemoprophylaxis
1) Purpose
2) Indication
3) Initiation
Purpose:
- Prevent influenza before exposure to virus
Indication:
1) Institutional outbreaks - Given to ALL unvaccinated individuals in institution
- E.g. In hospitals, long-term care facilities, nursing homes
- Rarely occurs –> institutions should have good infection control
2) Unvaccinated high risk individuals ≥ 3 months
- C/I to influenza vaccine
Initiation
- Initiate as soon as outbreak is identified
Influenza - Post-exposure chemoprophylaxis
1) Purpose
2) Indication
3) Initiation
Purpose:
- Prevent influenza after exposure
Indication:
1) ALL high risk individuals ≥3 months (vaccinated or unvaccinated)
2) Unvaccinated individuals ≥3 months who are household contacts of high risk individuals
Initiation
- Initiate as soon as possible - within 48h of exposure (less effective if given > 48h after exposure)
Antiviral treatment of influenza - Initiation
Initiate as soon as possible - Within 48h of symptom onset
- Benefit decreases if initiated > 48h of symptom onset
- May consider initiating in inpatient setting, even if patient presents > 48h after symptom onset (still some benefit e.g. decrease symptom duration, incidence of complications)
Antiviral treatment of influenza - Who to treat
Start antiviral (within 48h of symptom onset) for ANY ONE of the following:
1) Hospitalization
2) High risk individual
3) Severe, complicated or progressive illness
Other patients (e.g. outpatient setting): May be considered (if within 48h of symptom onset) BUT influenza is generally self-limiting –> usually not treated
Antiviral used in chemoprophylaxis / treatment of influenza
Oseltamivir
Oseltamivir - MOA
Neuraminidase inhibitor
- Inhibit cleavage of viral proteins –> viral proteins no longer functional
- Inhibit release of new virus –> inhibit viral replication
Note: Only effective against influenza A & B
Oseltamivir - Indications
Chemoprophylaxis & treatment of influenza
- 1st line
Oseltamivir - Dosing (Chemoprophylaxis)
PO 75 mg daily
- Renal dose adjustment needed
Duration:
Pre-exposure: 7 days after outbreak has resolved
Post-exposure: 7 days from exposure / from when starting Oseltamivir
Oseltamivir - Dosing (Treatment)
PO 75 mg BD
- Renal dose adjustment needed
Duration: 5 days
- May be extended in immunocompromised / critically ill patients (but not a lot of evidence supporting) this
Oseltamivir - ADR
Generally well tolerated
1) Headache
2) Mild GI effects
