Micro - Respiratory Tract Infections Flashcards
Define pneumonia and what are the S/S
Inflammation of the lung alveoli
fever, cough, SOB, pleuritic chest pain
What is the difference between upper and lower respiratory tract infection
URTI = sinusitis, tonsilitis
LRTI = bronchitis, pneumonia, empyema, bronchiectasis, lung abscess
What are the risk factors for pneumonia
Poor swallow (CVA, muscle weakness, alcohol)
Abnormal ciliary function (smoking, viral infection, Kartagener’s)
Abnormal mucous (cystic fibrosis)
Dilated airways: bronchiectasis
Defects in host immunity: HIV, immunosuppression
What is the difference between community and hospital acquired pneumonia
Community acquired (85%): usually pathogen is not identified
- Typical: Strep. pneumoniae (gram +ve), H. influenzae, Moraxella catarrhalis, staphylococcus aureus, klebsiella pneumoniae
- Atypical: legionella, mycoplasma, coxiella burnetii, chlamydia psittaci
Hospital acquired (15%): after 48hrs of hospital admission
- Enterobacteriaciae (e.g. E. coli, Klebsiella), pseudomonas, H. influenzae, staph aureus, acinetobacter baumanii, fungi (Candida)
What is the difference between typical and atypical infection
Typical = classic signs and symptoms, classic CXR changes (i.e. consolidation), respond to penicillin Abx
Atypical = no / atypical signs and symptoms, not in-keeping with CXR, don’t respond to penicillin Abx (no cell wall). May have extra-pulmonary features, e.g. hepatitis, hyponatraemia
How does causative organism of pneumonia change with age
0-1 months: E. coli, GBS, Listeria monocytogenes
1-6 months: Chlamydia trachomatis, S. aureus, RSV
6 months-5years: mycoplasma pneumoniae, influenzae
16-30 years: m. pneumoniae, Strep. pneumoniae
What are the signs and symptoms of pneumonia
Symptoms: SOB, cough + sputum, fever, rigors, pleuritic chest pain, malaise, N&V
Signs: pyrexia, tachycardia, tachypnoea, cyanosis, bronchial breathing, crackles, dullness to percussion
What are the key features of strep. pneumoniae infection
Most common (30-50%)
Gram +ve diplococci
Alpha-haemolytic (green tinge) and optochin sensitive
Rust-coloured sputum
Lobar on CXR
What are the key features of H. influenzae infection
Gram -ve cocco-bacilli (stain on chocolate agar)
Associated with smoking or pre-existing lung disease e.g. COPD
May produce beta-lactamase
What are the key features of moraxella catarrhalis infection
Gram -ve cocci
Associated with smoking
What are the key features of staph aureus pneumonia
Gram +ve cocci (Grape bunch clusters)
Associated with recent viral infection (influenza)
CXR: cavitating lesions
What are the key features of Klebsiella pneumoniae pneumonia
Gram -ve rods, enterbacter
Seen in alcoholics and the elderly
Causes haemoptysis
What are the key features of legionella pneumonia
Associated with travel, air conditioning, water towers
Buffered charcoal yeast extract
Causes hyponatraemia and hepatitis (Deranged LFTs), confusion, diarrhoea, abdo pain
What are the key features of chlamydia psittaci (psittacosis) pneumonia
Exposure to birds (parrots)
Causes splenomegaly, rash, haemolytic anaemia
Identified on serology
What are the key features of mycoplasma pneumonia
Seen in uni students/boarding schools
Causes erythema multiforme
Barking cough (dry) with normal CXR
Cold agglutinins
What are the key features of coxiella burnetii (Q fever) infection
Exposure to farm animals (aerosol or milk)
Causes hepatitis
Identified on serology
What are the key features of TB pneumonia
Presents with prolonged prodrome, fevers, weight loss, haemoptysis
CXR: upper lobe cavitation
Auramine stain and a Ziehl-Neelsen stain → Acid fast bacilli (red rods)
Cavitating caseating granuloma
What are the key features of pneumocystis jirovecii (including treatment)
Protozoa
CXR: bilateral infiltrative change
Detected by immunofluorescence or silver stain
Walk test (attaching an oxygen saturation probe and asking the patient to walk) will show desaturation on exertion
Presents with: dry cough, weight loss, SOB, malaise
Treatment/prophylaxis: co-trimoxazole (septrin)
What can aspergillus fumigatus infection cause
Allergic bronchopulmonary aspergillosis: chronic wheeze, eosinophilia, bronchiectasis
Aspergilloma: fungal ball → haemoptysis
Invasive aspergillosis: seen in immunocompromised patients (treat with amphotericin B)
Which respiratory tract infections are more common in the immunosuppressed
HIV: PCP, TB, cryptococcus neoformans
Splenectomy: encapsulated organisms (NHS)
Cystic fibrosis: Pseudomonas aeruginosa, Burkholderia cepacia
Neutropenia: Aspergillus → amphotericin B
What investigations should be done for pneumonia
Urinary antigens (legionella, strep. pneumoniae)
Sputum culture
Bronchial/broncho-alveolar lavage (esp. for HAP)
FBC, U&Es, CRP, blood cultures, serology (Chlamydia, legionella, coxiella), immunofluorescence (PCP)
CXR
Note: serology is only useful if paired (one unwell, one getting better)
How do you assess severity and necessity for admission in pneumonia
CURB-65
Confusion
Urea >7
Resp rate >30
BP <90
>65
1 → community treatment
2 → admit
3 → treat as severe infection
What is the management for typical CAP
Mild (CURB 0-1): amoxicillin
Moderate (CURB 2): amoxicillin + clarithromycin
Severe: Admit + Co-amoxiclav + clarithromycin
Penicillin allergy: cefuroxime + clarithromycin
What is the management for atypical CAP
Cell-wall active antibiotics (e.g. penicillins) do NOT work → so need agents that work on protein synthesis
Clarithromycin/erythromycin
Doxycycline
What is the management for HAP
First line: Ciprofloxacin ± vancocmycin
Second line/severe: tazocin (piptazobactam) + vancomycin
What is the management for aspiration pneumonia
Tazocin + metronidazole
What antibiotics are indicated for MRSA and pseudomonas
MRSA: Vancomycin
Pseudomonas: Piptazobactam OR ciprofloxacin ± gentamicin
What is bronchitis and what are the causes
Inflammation of medium-sized airways
Viruses (most common), strep. pneumoniae, H. influenzae, moraxella catarrhalis
What should be considered if there is failure to improve after antibiotics for pneumonia
Empyema/abscess
Proximal obstruction (tumour)
Resistant organisms (travel hx)
Not receiving/absorbing antibiotics
Immunosuppression
Other diagnosis (lung cancer, cryptogenic organising pneumonia
