Flashcards in Microbiology Lower Resp Tract infections Deck (102)
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1
Definition of LRTI:
• Any Infection of the respiratory tract from the vocal cords downwards
• Includes bronchi, bronchioles, alveoli, parenchyma, pleura and pleural cavities.
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Normal flora of the LRT
• The NORMAL LRT is bacteriologically strile
• Inhaled particles including micro-organisms are trapped by mucus and moved to the URT by epithelial cilia (mucociliary excalator)
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Abnormal flora of LRT
• Paralysis of cilia
• Excessive volume and/or viscosity of mucus
• Macro-ventiliation: LOC, Paralysis, ventilation, failure to protect LRT
• Failure to cough/loss of swallowing reflex
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Common colonisers of the LRT and origin
• “Colonisers” of LRT are often from URT such as Haemophilus influenza and Streptococcus pneumonia
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Iatrogenic causes of change of antibiotics
• Antibiotic therapy will effect URT colonisation.
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Types od LRTI
• Bronchiolitis (not covered) - viral
• Bronchitis (acute and chronic)
• Pneumonia
→ Community-acquired
→ Hospital-acquired
→ Aspiration
→ Immunocomprimised host
• Bronchiectasis
• Lung abscess/Emypema
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Acute Bronchitis causes
Most are Viral:
• Influenza
• RSV
• Rhinovirus
• Adenovirus
• Parainfluenza virus
Pertusis (bacterial cause)
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Manifestations with % frequency
• Cough (98%)
• Trouble sleeping (60%)
• Dyspnoea (50%)
• Nasal congestations (50%)
• Rhinorrhoea (50%)
• Sore throat (50%)
• Inability to work (33%)
• Fever (10-20%)
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Chronic obstructive airway disease – chronic bronchitis clinical definition
• Productive cough for more than 3 months per year for at least 2 years
• Wheezing
• Dyspnoea (shortness of breath)
COPD = chronic bronchitis with airflow limitation. Most chronic bronchitis develops COPD or time.
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Infective exacerbations of chronic bronchitis common
• 1-3 exacerbations per year in COPD patients
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Criteria used
Anthonisen criteria – used to optimising antibiotic selection in COPD patients
Antibiotic therapy indicated if two if:
• Increased breathlessness
• Increased sputum volume
• Increased sputum purulence
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Infective exacerbations of chronic bronchitis % viral/Bacteria
40% of acute exacerbations are viral
→ Patients with COPD may have colonisation of the LRT with organisms normally found in the URT such as H. influenza, M. cattarhalis
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Infective exacerbations of chronic bronchitis treatment
Amoxicillin
Tetracycline
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Community Acquired required length of stay and causative organisms
< 48 hours in hospital or in community (definition)
Usually bacterial Due to S. Pneumonia and sometimes-other organisms. Sometimes viral in children (always consider TB).
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Community Acquired treatment
Narrow spectrum therapy
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Hospital Acquired stay in hospital and causative organisms
>48 hours in hospital and not intubated on admission (definition)
Due to multi-resistant “hospital flora”
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Hospital Acquired treatment
Broad spectrum agents
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Pneumonia general clinical features
Fever/rigors/sweats
Headache
Confusion (esp. elderly)
Vomiting/diarrhoea
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Pneumonia localised clinical features
Breathlessness
Cough (may be productive)
Haemoptysis
Pleuritic chest pain
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Clinical Syndromes – Aspiration
(Macro aspiration) Inhalation of material, about 10% of community cases
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Predisposition to aspiration
Neurological deficit and commonly affects the posterior segment of right upper lobe
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Aspiration complication
Abscess formation
Can be associated with chemical pneumonitis
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Aspiration prevention
Protection of the airway
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Aspiration treatment
Antibiotics to cover URT flora e.g. penicillin or cephalosporin plus metronidazole.
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Acute community acquired pneumonia x-ray and the differentials for x-ray findings:
Lots of acute CXR shadowing
Sometimes non-infective e.g. Cardiac failure, chemical (smoke infection), severe infection elsewhere (ARDS)
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Acute-community acquired
Ilness progresses over days to a few weeks
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Chronic-community acquired
Illness progresses over weeks to a months
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Differentials for chronic community acquired pneumonaie
TB is the most important cause
Differential is wide including Vasculitides (non infectious)
Specialist assessment is needed.
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CAP epi
More common in water
Male/Female ratio 2:1
More common in older people
750,000 cases/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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