URTI Flashcards
Clinical presentation of pharyngitis (5 signs & symptoms)
- Acute onset of sore throat
- Pain with swallowing
- Fever
- Erythema and inflammation of the pharynx and tonsils (w/ or w/o patchy exudates)
- Tender and swollen lymph nodes
What bacteria most commonly causes pharyngitis?
Group A beta-haemolytic Streptococcus e.g. Streptococcus pyogenes -> strep throat
What are common complications of pharyngitis?
Complications usually occur 1-3 weeks later
Viral: self-limiting without complications
Bacterial/Streptococcus pyogenes:
- Acute rheumatic fever: serious, can damage heart or brain
- Acute glomerulonephritis
What are the common tests for pharyngitis? Why is testing not done usually?
Gold standard: throat culture - 24-48h, 90-95% sensitivity
Rapid antigen detection test (RADT) - minutes, 70-90% sensitivity
Not done: takes too long, use clinical diagnosis to initiate empiric antibiotics if necessary
Modified Centor Criteria for clinical diagnosis of pharyngitis
Add 1 point: - Fever > 38C - Swollen, tender anterior cervical lymph nodes - Tonsillar exudate - Absence of cough - Age: 3-14 y Minus 1 point if >45 y/o
Whether to initiate antibiotics for pharyngitis?
0-1 points: no testing due to low risk of S. pyogenes, presumed viral
2-3 points: test for S. pyogenes & treat if positive
- OR initiate empiric antibiotics
4-5 points: initiate empiric antibiotics due to high risk of S. pyogenes
Treatment for pharyngitis
1st line: PO penicillin VK 250mg QDS or 500mg BD
- paediatric: PO 250mg BD-TDS
Alternative:
PO amoxicillin 1g OD or 500mg BD
- paediatric: PO 50mg/kg/d OD or divided BD
PO clindamycin 300mg TDS
- paediatric: PO 7mg/kg TDS
PO cephalexin
PO clarithromycin
Duration: 10 days w/ clinical response in 24-48h
List 7 major symptoms for acute rhinosinusitis
- Purulent anterior nasal discharge
- Purulent/discoloured posterior nasal discharge
- Nasal congestion/obstruction
- Facial congestion/fullness
- Facial pain/pressure
- Hyposmia/anosmia: reduced/loss of sense of smell
- Fever
List 6 minor symptoms for acute rhinosinusitis
- Headache
- Ear pain, pressure, fullness
- Halitosis: bad breath
- Dental pain
- Cough
- Fatigue
Clinical diagnosis of sinusitis
> 2 major symptoms
OR
1 major + >= 2 minor symptom
What are some common bacterial causes of acute rhinosinusitis?
Most common: Streptococcus pneumoniae, Haemophilus influenzae
- Moraxella catarrhalis
- Streptococcus pyogenes
What are some viruses that cause URTIs?
Pharyngitis (>80%): rhinovirus, coronavirus, influenza, parainfluenza, Epstein-Barr
Sinusitis (>90%): rhinovirus, adenovirus, influenza, parainfluenza
AOM (40-45%): respiratory syncytial virus (RSV), rhinovirus, adenovirus, parainfluenza
What is the pathogenesis for pharyngitis and sinusitis?
Direct contact with droplets of infected saliva or nasal secretions
Pharyngitis: short incubation time of 24-48h
Sinusitis: usually preceded by viral URTIs (e.g. common
cold, pharyngitis)
- Inflammation: nasal mucosal secretions are trapped -> medium of bacterial trapping and multiplication -> sinus obstruction
Clinical diagnosis of bacterial sinusitis
Presence of sinusitis (based on major/minor symptoms)
AND
Presence of bacterial sinusitis: any one criteria
1. Persistent symptoms > 10 days & not improving
2. Severe symptoms at onset
- Purulent nasal discharge x3-4 days or high fever > 39C
3. “Double sickening”: worsening symptoms after 5-6 days after initial improvement (recovery of viral URTI)
Treatment of bacterial sinusitis
1st line antibiotics:
PO amoxicillin 1g TDS
PO amoxicillin/clavulanate 625mg TDS or 1g BD
- Paediatric: either PO amox or amox/clav 80-90mg/kg/day divided BD
Alternative antibiotics
Respiratory fluoroquinolones:
- PO levofloxacin 500mg OD
- PO moxifloxacin
PO trimethoprim/sulfamethoxazole
PO cefuroxime
Duration: 5-10 days (adult), 10-14 days (paediatric)
Which antibiotics are not suitable for bacterial sinusitis? Why?
- Local S. pneumoniae resistant to macrolides & tetracycline
- > Clarithromycin, azithromycin & doxycycline not appropriate - Ciprofloxacin has poor activity against S. pneumoniae
- > not a respiratory fluoroquinolone
What are the mechanisms of resistance for Streptococcus pneumoniae and Haemophilus influenzae?
S. pneumoniae: multi-step penicillin binding proteins (PBPs) mutation -> each step increases penicillin MIC
- uncommon locally
Haemophilus influenzae: beta-lactamase production (inhibit with beta-lactamase inhibitor e.g. clavulanate)
- around 18% locally
When should amoxicillin/clavulanate be used for treatment of sinusitis?
Resistant Haemophilus influenzae: need beta-lactamase inhibitor -> clavulanate
Indications:
- Recent course of antibiotics
- Recent hospitalization
- Failure to improve after 72h of amoxicillin
Why is amoxicillin preferred over penicillin for sinusitis?
More favourable PK (higher systemic concentration)
High dose amoxicillin more effective: 80-90mg/kg/day (paediatrics) or 1g (adults)
-> Compared to standard dose: 45mg/kg/day (paediatrics), 250-500mg (adults)
What is the clinical presentation of acute otitis media? (5 signs and symptoms)
Mostly paediatric patient <5y (nasal discharge backflow into eustachian tube)
- Ear pain (otalgia), ear discharge (otorrhea), ear popping, ear fullness
- Hearing impairment
- Dizziness
- Fever
- Non-specific for young infants: ear rubbing, excessive crying, changes in sleep or behaviour patterns
Risk factors for AOM
- Siblings
- Day care
- Supine during feeding
- Exposure to tobacco smoke at home
- Pacifier use
- Winter season
Prevention of AOM
- Avoid exposure to tobacco smoke
- Exclusive breastfeeding for 1st 6 months
- Minimize pacifier use
- Vaccinations: influenza, pneumococcal, Haemophilus influenzae type B vaccine (HiB)
Pathogenesis of AOM
2 pathways from viral URTI to reflux of secretions into middle ear -> medium for bacterial accumulation/growth
- Nose sniffling
- Secretions & inflammation -> eustachian tube obstruction -> negative eustachian tube pressure
Which bacteria can cause AOM?
Streptococcus pneumoniae
Haemophilus influenzae
Moraxella catarrhalis
How is AOM diagnosed?
Pneumatic otoscope Criteria: - Acute onset <48h - Otalgia (rubbing, holding, tugging) or erythema of tympanic membrane - Bulging of tympanic membrane
When should we consider an observation period instead of starting antibiotics for AOM?
Observation period: supportive care 48-72h, give abx only if worsen/fail to improve
Fulfill all 5 criteria:
- >6 months y/o
- Non-severe illness: NO moderate-severe otalgia, otalgia >48h or fever >39C in last 48h
- No otorrhea: if bilateral only >2y/o
- Possible for close follow-up
- Shared decision making with parent/caregiver
What are the issues with prescribing antibiotics for AOM?
Can’t distinguish between bacterial or viral etiologies
Overprescribing abx -> resistance
Bacterial: prompt abx initiation reduces symptoms by 1 day -> 80% cases resolve in 3-4 days w/o abx
1st line treatment for AOM
1st line: PO amoxicillin 80-90mg/kg/day divided into BD
- Provided that (all): no amoxicillin in last 30 days, no concurrent purulent conjunctivitis (likely S. aureus, can’t be covered), not allergic to penicillin
Alternative: PO amoxicillin/clavulanate 80-90mg/kg/day divided into BD
- If (any 1): amoxicillin in last 30 days, concurrent purulent conjunctivitis, or Hx of AOM non-responsive to amoxicillin
Why is ceftazidime not suitable for treatment of AOM?
Poor gram +ve activity against S. pneumoniae
What are some alternative treatment options for AOM for individuals with penicillin allergies?
PO cefuroxime 30mg/kg/day divided BD or IM ceftriaxone: mild penicillin allergy
PO clindamycin: severe penicillin allergy, only effective against S. pneumoniae
What is the treatment duration for AOM?
10 days: <2 y/o or severe symptoms
7 days: 2-5 y/o w/ non-severe symptoms
5-7 days: >6 y/o w/ non-severe symptoms
What are the differences in clinical presentation between influenza & the common cold?
Influenza has more severe symptoms:
Abrupt onset w/ fever, body aches, chills, chest discomfort, headache
Both go through 24-72h of incubation period
List the 3 types of influenza and their differences
Influenza A: human, swine, equine, avian, multi-species
- most severe illness, significant mortality in young persons
- epidemics & pandemics
Influenza B: humans only
- severe illness in older adults or high risk persons
- less severe epidemics
Influenza C: humans & swine
- mild respiratory illness without seasonality
How is influenza tracked in Singapore?
Number of people visiting polyclinics for acute respiratory tract infections
Bimodal distribution: Dec-Feb & May-July
Complications of influenza
- Viral pneumonia (LRTI)
- Post-influenza bacterial pneumonia (esp S. aureus has high mortality >30%)
- Respiratory failure
- Exacerbate underlying cardiac or pulmonary comorbidities
- Febrile seizures
- Myocarditis or pericarditis
High-risk for influenza complications
Age: children <5y or elderly >65y
Pregnant women or within 2 weeks post-partum
Residents of nursing homes or long-term care facilities
Obese individuals w/ BMI >40kg/m2
Chronic medical conditions: asthma, COPD, heart failure, DM, CKD, immunocompromised, etc
What is in the influenza vaccine?
Inactivated trivalent or quadrivalent vaccine -> given IM once per year
- Indicated for everyone >6mo
Why is chemoprophylaxis not recommended for influenza?
Increases risk of resistance -> avoid sub-therapeutic dosing
Diagnosis of influenza
Inpatient: reverse-transcriptase polymerase chain reaction (RT-PCR)
Outpatient: treat empirically
Viral cultures not recommended
When should treatment of influenza be initiated?
Initiate ASAP within 48h of onset if any 1:
- Hospitalized
- High risk for complications
- Severe, complicated or progressive illness
Consider also if presenting within 48h of symptom onset -> period with greatest benefit in preventing influenza complications
Treatment of influenza
PO oseltamivir 75mg BD for 5d
- May prolong if patient is immunocompromised or critically ill
*Clinically significant: active against influenza A and B
MOA: neuraminidase inhibitor -> interfere with protein cleavage & inhibit release of new virus
Well-tolerated, minimal side effects: headache, mild GI
