Respiratory Tract Infections Flashcards
How do we divide RTIs?
Upper and lower
What are the URTIs?
o Sinusitis
o Tonsillitis
What are the LRTIs?
- Bronchitis
- Pneumonia
- Empyema
- Bronchiectasis
- Lung abscess
What do we get RTIs?
- 18yo female; fever, cough and malaise
- Diagnosed with flu by GP (no ABx given)
- Attended A&E with…
- T 38C
- 87% sats on room air
- Chest clear, RR 24
- Bloods (WCC 40.8, Neut 36.3, CRP 63)
CXR → double heart border (‘Sail’ sign)
densely consolidated and collapsed lower lobe
- 18yo female; fever, cough and malaise
- Diagnosed with flu by GP (no ABx given)
- Attended A&E with…
- T 38C
- 87% sats on room air
- Chest clear, RR 24
- Bloods (WCC 40.8, Neut 36.3, CRP 63)
What is the most likely organism?
Streptococcus pneumoniae
What is happening?
- Alpha-haemolytic and optochin-sensitive
- Gram-positive cocci (chains and pairs)
What percentage of.community-acquired pneumonia is strep. pneumoniae responsible for?
30-50%
What does acute onset of strep. pneumonia cause?
- Severe pneumonia
- Fever and rigors
- Lobar consolidation
What is strep pneumonia almost always sensitive to?
- Almost always penicillin-sensitive
- Penicillin-resistance strains may be imported from Southern Europe
Define pneumonia.
inflammation of the lung alveoli
What is the mortality of pneumonia?
Patients are sick with a mortality of 5-10%
20-40% admitted to hospital
How does pneumonia present?
- Fever
- Cough
- Abnormal CXR
- Pleuritic chest pain
- SoB
How do we classify pneumonia?
- Community-acquired
- Hospital-acquired/nosocomial (i.e. ventilator-associated)
What are the underlying factors behind pneumonia that need to be considered?
- Pre-existing lung disease
- Immunocompromise
- Geography, seasons, epidemics
- Travel, exposure to animals
Why is no microbiological ID made in most cases of CAP?
this is often due to difficulty obtaining a good sputum sample and because of early treatment with antibiotics
What are the main organisms causing CAP?
- Streptococcus pneumoniae
- Haemophilus influenzae
- Moraxella catarrhalis
- Staphylococcus aureus
- Klebsiella pneumoniae
How do pathogens causing CAP differ by age?
What are the causative organisms of CAP?
- TYPICAL (85%)
- Streptococcus pneumoniae
- Haemophilus influenzae
- ATYPICAL (15%)
- Legionella
- Mycoplasma
- Coxiella burnetii (Q fever) from exposure to farm animals
- Hepatitis
- Chlamydia psittaci (Psittacosis) from exposure to birds
- Splenomegaly, rash, haemolytic anaemia
What are the symptoms of CAP?
- SoB
- Cough ± sputum
- Fever
- Rigors
- Pleuritic chest pain
- Malaise, N&V
What are the signs of CAP?
- Pyrexia
- Tachycardia
- Tachypnoea
- Cyanosis
- Bronchial breathing
- Crackles
- Dullness to percussion/tactile vocal fremitus
What investigations should be done on CAPs?
- FBC, U&E, CRP
- BCs, Sputum MC&S
- ABGs
- CXR
What scoring system do we use to assess severity of CAP?
- Confusion
- Urea > 7 mmol/L
- RR > 30
- BP < 90 systolic, < 60 diastolic
- 65+ years
2 = consider admitting
2-5 = manage as severe / consider ITU
Define bronchitis.
inflammation of medium-sized airways
Who is bronchitis usually seen in?
Smokers
How does bronchitis present?
- Cough
- Fever
- Increased sputum production
- Increased shortness of breath
What does a CXR usually show for bronchitis?
Normal
What organisms cause bronchitis?
- Viruses
- Streptococcus pneumoniae
- Haemophilus influenzae
- Moraxella catarrhalis
What is the tx for bronchitis?
- Bronchodilation
- Physiotherapy
- Antibiotics
- 56yo man; flu-like illness
- Presented with cough, fever, haemoptysis, pyrexia (but not severely unwell)
- What organism would you suspect?
- Strep pneumonia
- H. influenzae
- Staph aureus
- Klebsiella
Cavitation on X ray
H. influenzae
- Gram-negative cocco-bacilli - H. influenzae
- (stain on chocolate agar)
What percentage of CAPs does H. influenza cause?
15-35%
What resistance can H.influenzae have?
- May produce beta-lactamase
When is H.influenzae infection more common?
With pre-existing lung disease
- 62yo man; SOB
- Confusion, smoker, 91% saturation on room air, chest exam normal, hyponatraemia
- What is the likely organism?
- Moraxella catarrhalis
- Mycobacterium TB
- Legionella
- Staph aureus
- CMV
CXR - bilateral interstitial change
Legionella pneumophilia
- It is grown on a buffered charcoal yeast extract
How is legionella spread? What does it cause?
- Spread via inhalation of infected water droplets - aerosol
- Environmental outbreaks
- Associated with:
- Confusion
- Abdominal pain
- Diarrhoea
- Lymphopaenia
- Hyponatraemia
- Can cause multi-organ failure
What is atypical pneumonia caused by?
- Pneumonia caused by organisms without a cell wall:
- Mycoplasma
- Legionella
- Chlamydia
- Coxiella
What is atypical pneumonia caused by?
- Pneumonia caused by organisms without a cell wall:
- Mycoplasma
- Legionella
- Chlamydia
- Coxiella
What antimicrobials (don’t/do) work on atypical pneumonias?
- Cell-wall active antibiotics (e.g. penicillins) do NOT work → so need agents that work on protein synthesis
- Macrolides (clarithromycin/erythromycin)
- Tetracyclines (doxycycline=
What are extrapulmonary features of atypical pneumonias?
- (e.g. hepatitis, hyponatraemia) – characteristic of atypical pneumonias
What percentage of CAPs are caused by atypical pneumonias?
- Account for 20% of CAP
What characteristics are found in atypical pneumonias?
- Often have a flu-like prodrome before fever and pneumonia
- Extra pulmonary complications
How do we diagnose legionella pneumophila and how is it treated?
- Investigation: urinary antigens
- Sensitive to macrolides
Where do we commonly see Coxiella burnetii? How is it transmitted? How is it investigated? How is it treated?
- Common in domesticated farm animals
- Transmitted by aerosol or milk
- Investigation: serology
- Sensitive to macrolides
How is chlamydia psittaci spread? How is it investigated? How is it managed?
- Spread from birds by inhalation
- Investigation: serology
- Sensitive to macrolides
- 74yo woman
- SOB, fever (38.5C), right-sided pleuritic chest pain, reduced percussion note & decreased air entry right base
- PMHx IHD, CABG, AF;
- DHx warfarin
- Otherwise well
- Admitted → commended on cefuroxime and doxycycline continued to spike fevers
- What is the possible diagnosis?
- A) Tuberculosis
- B) Empyema
- C) Mesothelioma
- D) MRSA pneumonia
- E) Aspiration pneumonia
- What is the possible diagnosis?
- CXR → homogenous shadowing with meniscus level of right side (CT → empyema with collapsed lung underneath)
- Empyema
- These are difficult to treat because they have a wall around them and the pus itself is very acidotic which inactivates the antibiotics → hence why she continued to spike fevers even on ABx
Why do patient fail to improve on treatment for empyema?
- Empyema/abscess
- Proximal obstruction (tumour)
- Resistant organisms (travel hx)
- Not receiving/absorbing antibiotics
- Immunosuppression
- Other diagnosis (lung cancer, cryptogenic organising pneumonia
Bilateral interstitial changes
SARS-CoV-2
Focal changes - SARS-CoV-2
- 21yo male, from Ecuador
- Cough and WL
- U&Es normal
- Hb 10.4
- WCC 9.8
- HIV -ve
- CRP 173
- Alb 31
- What is the causative organism?
- A) Staphylococcus aureus
- B) Aspergillus fumigatus
- C) Mycobacterium tuberculosis
- D) Haemophilus influenzae
- E) Pneumocystis jiroveci
- CXR right-sided apical shadowing → diagnosed TB
What are clues for a dx of TB?
- Clues: Geographical exposure/Ethnicity, Prolonged prodrome, Fevers, Weight loss, Haemoptysis
- CXR: classically upper lobe cavitation (but can vary)
- TB
- Staining:
- An auramine stain and a Ziehl-Neelsen stain will be done
- Red rods are the acid-fast bacilli
Define HAP.
- A pneumonia onset >48 hours in hospital
What do patients with HAP usually have?
- Patients have often had previous antibiotics and maybe even ventilation
- Bronchial lavage is desirable (differentiate upper respiratory from lower respiratory flora)
What is the aetiology of hospital acquired acquired pneumonias?
Enterobacteriaciae (e.g. E. coli, K. pneumoniae)
- 64yo retired general
- Treated for lymph node TB
- Increasing SOB, non-productive cough, chest exam normal
- What organism is likely to have caused this?
- A) Aspergillus fumigatus*
- B) Influenza*
- C) Mycoplasma pneumoniae*
- D) Cytomegalovirus (CMV)*
- E) Pneumocystis jiroveci*
- CXR → bilateral ground-glass shadowing (“bat’s wing”)
- Pneumocystitis jirovecii
What type of organism is pneumocystitis jirovecii? Where is it found?
Protozoan
Ubiquitous in the environment
What is the presentation of pneumocystis jirovecii? What sign would you see on XR?
- Dry cough
- Weight loss
- SOB
- Malaise
Bat’s wing
What are the Ix and Mx of pneumocystis jieovecii?
NOTE: the walk test (attaching an oxygen saturation probe and asking the patient to walk) will show desaturation on exertion
- Investigations: bronchoalveolar lavage
- Treatment: co-trimoxazole (septrin)
- Prophylaxis: co-trimoxazole
Pneumocystis jirovecii
- 22yo man, chemotherapy for leukaemia
- Prolonged neutropenia (<1.0), fevers, raised inflammatory markers
- ABx so far : meropenem, ciprofloxacin, vancomycin, tazocin, ganciclovir
A)MRSA
B)Aspergillus sp.
C)Mycobacterium tuberculosis
D)CMV
E)Pseudomonas aeruginosa
- CT thorax : non-specific (interstitial) changes on the CT scan → Aspergillus fumigatus
What are the different presentations of aspergillum fumigatus?
Allergic bronchopulmonary aspergillosis
- Chronic wheeze
- Eosinophilia
- Bronchiectasis
Aspergilloma
- Fungal ball, often in pre-existing cavity
- May cause haemoptysis
Invasive aspergillosis
- Immunocompromised
- Treatment: amphotericin B
Aspergillus fumigatus
What infections are you likely to get with
- HIV
- Neutropenia
- BM transplant
- Splenectomy
- HIV → PCP, TB, Atypical mycobacteria
- Neutropoenia → Fungi (e.g. Aspergillus spp)
- Bone Marrow Transplant → CMV
- Splenectomy → Encapsulated organisms (S. pneumoniae, H. influenzae, malaria)
- Anything can do anything
What different samples can be sent in LRTIs
- Sputum/induced sputum
- Blood cultures
- BAL
- Pleural fluid
- Antigen tests
- Antibody tests
- Immunofluorescence
- PCR
For what should antigen tests be sent?
- Limited urine antigen tests available for:
- Legionella pneumophila
- Streptococcus pneumoniae
- Send in severe CAP
When should antibody tests be collected? What are we looking for? What are the most useful organisms to test for?
- Only useful on paired serum samples (one acutely unwell and another when getting better)
- Usually collected on presentation and 10-14 days later
- Looks for a rise in antibody level over time
- Most useful organisms to send antibody tests for because they are difficult to culture:
- Chlamydia
- Legionella
What does immunofluorence do? What is it used for? What is the most common one used?
- Antibody is labelled with fluorescent dye
- Often used in virology
- PCP immunofluorescence is the most commonly used one in microbiology labs
- PCP may also be detected by Silver stain in cytology labs
How would you choose abx tx for RTI?
Describe the abx framework
What is the empirical therapy of CAP?
-
Each hospital has its own guidelines
- Mild-Moderate: Amoxicillin [OR erythromycin/clarithromycin]
- Moderate-Severe
- Needing hospital admission: Co-amoxiclav (augmentin) AND clarithromycin
- Allergic: Cefuroxime AND clarithromycin
What is the empirical therapy of HAP?
What is the empirical therapy of HAP?
- 21yo man, no PMHx, smoker, drinker
- Presented cough, SOB, sats 89% room air, hypotensive
- How would you treat this pt?
- A)Amoxicillin
- B)Piperacillin/tazobactam and vancomycin
- C)Co-amoxiclav
- D)Co-amoxiclav and clarithromycin
- E)Rifater, isoniazid, pyrazinamide and ethambutol
- What other mx should be given?
- CXR : RUZ pneumonia
- Co-amoxiclav and clarithromycin
- Fluid resuscitation
- Supplemental O2
- Senior support requested
How do we prevent pneumonia?
- Smoking cessation
- Vaccination:
- Childhood immunisation schedule
- Adults → influenza annually, pnemovax every 5 years
