Any infection of the respiratory tract from the vocal cords downwards - includes: Bronchi Bronchioles Alveoli Parenchyma Pleura Pleural cavities Normally bacteriologically sterile Inhaled particles including microorganisms are trapped by mucus and moved to the upper respiratory tract by epithelial cilia (mucociliary escalator)

Symptoms Cough Trouble sleeping Dyspnoea Nasal congestion Rhinorrhea Sore throat Fever (uncommon) Causes Mostly viral: Influenza RSV Rhinovirus Adenovirus Parainfluenza virus Pertussis - !

Chronic bronchitis - clinical definition: Productive cough for more than 3 months per year for the past 2 years Wheezing Dyspnoea (SOB) Most chronic bronchitis patients develop COPD over time = chronic bronchitis + airflow limitation

Lower Respiratory Tract Infections Flashcards by George Wellby

Definition of LRTI

Any infection of the respiratory tract from the vocal cords downwards - includes:
- Bronchi
- Bronchioles
- Alveoli
- Parenchyma
- Pleura
- Pleural cavities
Normally bacteriologically sterile
- Inhaled particles including microorganisms are trapped by mucus and moved to the upper respiratory tract by epithelial cilia (mucociliary escalator)

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Pathogenesis of LRTIs

Paralysis of cilia
Excessive volume and/or viscosity of mucus - e.g. CF
LOC, paralysis, ventilation ==> failure to protect LRT
Failure to cough/loss of swallowing reflex
“Colonisers” of LRT are often from URT such as:
- Haemophilus influenzae
- Streptococcus pneumoniae
Antibiotic therapy will affect URT colonisation

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Acute Bronchitis

Symptoms
- Cough
- Trouble sleeping
- Dyspnoea
- Nasal congestion
- Rhinorrhea
- Sore throat
- Fever (uncommon)
Causes
- Mostly viral:
  - Influenza
  - RSV
  - Rhinovirus
  - Adenovirus
  - Parainfluenza virus
- Pertussis - !

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Chronic Bronchitis

Chronic bronchitis - clinical definition:
- Productive cough for more than 3 months per year for the past 2 years
- Wheezing
- Dyspnoea (SOB)
Most chronic bronchitis patients develop COPD over time = chronic bronchitis + airflow limitation

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Chronic Bronchitis - Infective Exacerbations

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Pneumonia - Clinical Features

General:
- Fever/rigors/sweats
- Headache
- Confusion (especially elderly patients)
- Vomiting/diarrhoea
Localised:
- Breathlessness
- Cough (may be productive)
- Haemoptysis
- Pleuritic chest pains

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Pneumonia - Investigations

General
- Sats
- ABGs
- FBC
- U&Es
- CRP - useful for monitoring progress of therapy
- CXR
Microbiological
- Serum - stored acutely 2-3 weeks later used retrospectively to diagnose
- Blood cultures - only positive in 15% of severe cases
- Sputum - shown to be of no clinical value except in cases of TB or Legionella
- Bronchio-alveolar lavage - optimal sample but only used in severe cases as invasive
- Urine - test for antigen to Legionella/S.pneumoniae

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Pneumonia - Aspiration Pneumonia

Inhalation of material; about 10% of community cases
Usually neurological problem predisposing
Commonly affects posterior segment of right upper lobe
Can lead to abscess formation
May be associated with chemical pneumonitis - inflammation of the lung caused by inhaling irritants
Protection of airway important in prevention
Treat with antibiotics to cover URT flora e.g. penicillin or cephalosporin plus metronidazole

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Pneumonia - Acute Community Acquired

Common
If present less than 48 hours into a hospital admission - community acquires
Most commonly due to:
- Streptococcus pneumoniae
- Haemophilus influenzae
Specific causative organisms:
- Staphlococcus aureus in flu epidemics
- Kleibsiella pneumoniae in diabetics and alcoholics = severe
- *M.catarrhalis *in COPD
Sometime viral in children
Always consider TB
Narrow spectum therapy

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Pneumonia - Chronic Community Acquired

Uncommon
Illness progresses over weeks to months
TB is the most important cause
Wide differential including vasculitides
Specialist assessment needed

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Community Acquired Pneumonia - Epidemiology

More common in winter
Male 2:1 female
More common in elderly
750,000 cases a year in UK
- 150,000 consult GP
  - 50,000 hospitalised
10% mortality among hospitalised patients
Up to 50% mortality if severe

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Assessing Severity of CAP

CURB-65 score
- Confusion - AMT of 8 or less
- Urea raised > 7mmol/l
- Respiratory rate >30/min
- Blood pressure: systolic <90mmHg +/- diastolic <60mmHg
- 65 and over
  - >/= 3 - admit to hospital (mortality 22%)
  - 1 or 2 - hospital referral and assessment
  - 0 - treat in community
Additional adverse features:
- Hypoxaemia: PaO2 <8kPa, SaO2 <92%
- Bilateral or multilobar involvement on CXR

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Typical vs Atypical Pneumonia

Two groups of pathognes
- Respond to different antibiotics
- Clinical spectrums differ
- Cannot tell clinical difference in individual case
Typical:
- Often lobar
- Caused by: Streptococcus pneumoniae
- Amoxicillin sensitive
- Sometimes macrolide sensitive
Atypical:
- Often multisystem, multilobar
- Causative organisms: Mycoplasma, Chlamydia, Coxiella, Legionella
- Amoxycillin resistant
- Macrolide sensitive

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Streptococcus Pneumoniae

Microbiology:
- Gram positive diplococci
- Alpha (incomplete) haemolysis
- Draughtsmen colonies
Colonises the nose
Transmitted person-person
Can invade, causing:
- Pneumonia
- Meningitis
- Endocarditis
- Bacteraemia (may be only manifestation in toddlers)
Sensitive to: amoxycillin and doxycycline, levofloxacin/moxifloxacin
Penicillin resistance increasing, although rare in UK
Significant cause of mortality amongst susceptible individuals e.g elderly, renal failure, splenectomy
Vaccine available against 23 serogroups plus new heptavalent conjugate vaccine

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Haemophilus Influenzae

Several serovars resident in the nose
Transmitted person-person
Vaccine preventable
Capsular strain (a-f)
- Associated with invasive infection including, meningitis, epiglottitis (HiB vaccine effective)
Non-capsular strains
- Associated with mucosal infections including, otitis media, sinusitis and exacerbations of COPD (HiB vaccine ineffective)
Can invade, causing
- Pneumonia
- Meningitis
- Bacteraemia
- Epiglottitis
- Septic arthritis
Requires haem (X) and NAD (V) for growth
Sensitive to amoxicillin
- 20% are b-lactamase positive
  - These are sensitive to cefuroxime and co-amoxiclav

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Mycoplasma Pneumoniae

Occurs in epidemics every 3-4 years
Cause of primary atypical pneumonia
Human to human transmission
Most common in children and young adults
Rare complications include myringitis and encephalitis
Diagnosis is by serology
Microbiology:
- Lacks classical peptidoglycan cell wall
- Resistant to beta-lactam antibiotics
- Sensitive to macrolides, tetracyclines and quinolones

Legionella Pneumonphila

Can survive and multiply inside macrophages
Can cause:
- Mild influenza-like URTI = Pontiac fever
- Severe pneumonia with multi-organ failure = Legionnaire’s disease
  - >50% of cases associated with travel
  - Breeds in stagnant water then spread by cooling tower

Chlamydia Pneumoniae and Chlamydia Psittacii

Obligate intracellular parasites
Sensitive to macrolides, tetracyclines and quinolones
C.pneumoniae usually self-limiting and mild
- Human to human transmission
C.psittacii can cause severe pneumonia
- Zoonotic infection from birds
- Occupational disease of poultry processing industry

Coxiella Burnetii

Causes Q fever
Spread can be airborne, through infected milk, faeces and urine of farm animals
Can cause severe pneumonia
Diagnosis is by serology (Phase 1 and 2 antibodies)
Can lead to chronic disease and endocarditis
Best treated with tetracyclines

Community Acquired Pneumonia - Empirical Treatment

At home
- Oral
  - Amoxicillin 500mg tds
    - Alternatively erythromycin 500mg qds or clarithromycin 500mg bd
In hospital:
- Oral
  - Amoxicillin 500mg tds plus erythromycin 500mg qds or clarithromycin 500mg bd
    - Alternatively *levofloxacin *500mg od
- IV
  - Ampicillin 500mg qds or benzypenicillin 1.2g qds plus erythromycin 500mg qds or clarithromycin 500mg bd

MRSA - Hospital Acquired

Who?
- Elderly
- Debilitated
- Critically/chronically ill
What?
- Bacteraemia
- UTI
- Skin and soft tissue infection
How?
- Nosocomial
Risk factors?
- History of MRSA infection
- Recent surgery
- Admission to a hospital or nursing facility
- Anitbiotic use
- Dialysis
- Permenant indwelling catheter
Antibiotics
- Multi-drug resistant
SSCmec (mobile gene element encoding methicillin resistance)
- I
- II
- III
PVL toxin:
- Rare

MRSA - Community Acquired

Who?
- Young healthy people: high school, college and professional athletes
What?
- Skin and soft tissue infections
- Pneumonia
How?
- May spread in families and sports teams
Risk factors?
- Recent antibiotic therapy
- Minor skin trauma
- Unusual grooming habits
Antibiotics:
- Resistant only to Beta-lactam antibiotics
SSCmec (mobile gene element encoding methicillin resistance)
- IV
PVL toxin
- Common

PVL S.aureus Pneumonia

Panton-Valentine Leukocidin (PVL) is a cytotoxin produced by some strains of S.aureus that can destroy white blood cells and cause extensive tissue necrosis and severe infection
Consider PVL S.aurus pneumonia if:
- Previously fit and well
- ‘Flu-like’ illnesss
- Multi-lobar involvement on CXR +/- effusions and cavitation
- Haemoptysis
- Hypotension
- Leucopaenia
- High CRP
- Sputum microscopy showing sheets of staphlococcal-like Gram positive cocci

Hospital Acquired Pneumonia

3^rd most common nosocomial infection
Occurs 0.5-1/100 hospital admissions
Cause of considerable morbidity/mortality
Defined as occurring >48 h after admission
Diagnosed by culture, antigen detection or serology
Treatment depends on organism involved - if unknown need to cover both S. aureus and P. aeruginosa the two most common causative organisms
- Early onset infection (<5 days following hospital admission) - *co-amoxiclav *or cefuroxime
  - If recently on antibiotics or other risk factors then - 3rd generation cephalosporin (*cefotaxime *or ceftriaxone) or a fluoroquinolone or piperacillin/tazobactam

Pneumonia - Immunocompromised

* Different groups vary in susceptibility to microorgaisms: neutropaenia, HIV, organ transplantation, steroid treatment * Lack of neutrophils predisposes to: * Gram negatives eg: * *Pseudomonas* * Coliforms * Gram positives eg: * *Staphylococcus aureus* * Viridans streptococci * Lack of appropriate T-cells predisposes to: * Intracellular pathogens eg. Mycobacterium species * Viruses eg. CMV and adenovirus * Fungi eg. *Cryptococcus neoformans* and *Aspergillus* species

Pneumonia - Immunocompromised - Diagnosis and Treatment

* Can be very difficult * Strenuous attempts should be made to help identify offending pathogen e.g use of CT scan, bronchoscopy, BAL, needle biopsy * Treatment may have to cover a wide range of pathogens * Recovery of neutrophil function/T-cell defect will improve prognosis * Prophylaxis required in selected patients

Pneumonia - Pneumocystis Jiroveci (Carinii)

* HIV related illness * Occurs with CD4 * Fungus: Pneumocystis * Pneumonia, onset over several days ==\> weeks * Important cause of death in AIDS

Pneumonia - Pneumocystis Jiroveci (Carinii) - Diagnosis and Treatment

* Diagnosis requires induced sputa or BAL sample * Analysed by cytology * Pneumocystis can’t be cultured * Rx: * Refractory to normal antibiotics * Responds to co-trimoxazole (Septrin) + steroids * Prophylaxis given if CD4\< 200

Bronchiectasis and Cystic Fibrosis

* Bronchiectasis is due to abnormal structure of bronchi leading to inflammation and obstruction * Cystic fibrosis leads to abnormal and tenacious mucus in bronchial tree * Both results in cycles of colonization/ infection/ tissue damage * Colonising organisms: * *Staphylococcus aureus* * *Haemophilus influenzae* * *Moraxella catarrhalis* * *Pseudomonas aeruginosa* * Follow-up involves: * Montioring clinically * Further X-rays to: * Confirm diagnosis * Exclude complications

Lower Respiratory Tract Infections - Complications - Lung Abscess

* May be due to aspiration, pneumonia, haematogenous spread or malignancy * Aspiration usually polymicrobial * Haemotogenous abscess usually due to *Staphylococcus aureus* * Rarer causes include: * *Klebsiella pneumoniae* * *Pseudomonas aeruginosa* * Fungi

Lower Respiratory Tract Infections - Complications - Pleural Effusion

* Pleural effusions complication of chronic bronchiecatasis or CF * Diagnosis made by diagnosic tap to determine types: * Parapneumonic effusion: * Reactive - non-infective * pH\>7.2 * Manage conservatively * Empyema * Infected * pH * Needs drainage +/- surgery