Lecture 14- Lower respiratory tract infections and pneumonia Flashcards
Lower respiratory tract infections (LRTI) are a leading cause of death in the
elderly
Course of typical infection
- Alveolar macrophages fails to stop pathogen
- Cytokines to recruit more macrophages
- Inflammation= increased permeability
- More WBC/proteins
- Neutrophils
- Lymphocytes
- Antibodies to aid macrophage
course of typical infection outside the lungs
- Inflammatory mediators (cytokines) into systemic circulation
- Physiological- activates bone marrow/more CO and raised body temp
- Dysregulation/ pathological inflammation– signs of tissue injury/ organ injury (multi-organ failure- low BP due to vasodilation of blood vessels in response to inflammation e.g. liver and kidney failure due to low BP
Inflammation=
increases blood supply and increases WBC to the site of infection via the release of cytokines
- Damages lung tissue
common microbiota of the resp tract
- Viridians streptococci
- Neisseria sp
- Anaerobes candida sp
Less common microbiota of respiratory tract
- Streptococcus’s pneumoniae
- Streptococcus pyrogens
- Haemophilus influenzae
Others
- Pseudomonas
- E.coli
Upper resp tract=
nasal cavity to the larynx
lower resp tract
trachea –> lungs
lungs are not
sterile
- normal alveolar microbiota
- aspiration
- blood stream spread
- direct spread
Defences of resp tract
- Muco-ciliary clearance mechanisms nasal hairs, ciliated columnar epithelium of the resp tract
- Cough and sneezing
- Respiratory mucosal immune system
- Lymphoid follicles of the pharynx and tonsils, alveolar macrophages, secretary IgA and IgG
- Alveolar microbiota
what causes dyrefulation of inflammation
- the pathogens virulence factors
- host factors
- drugs
pathogen virulence factors
What causes dysregulation of inflammation: host factors
- Over 75
- Lifestyle
- Smoking (abnormal ciliary function)
- Alcohol/drugs
- Chronic lung disease e.g. bronchiectasis, CF
- Aspiration
- Change in level of consciousness
- Dysphagia
- Wearing dentures whilese sleeping
- Immunocompromised
- DM
- HIV
- Metabolic
- Malnutrition
- Hypoxaemia
- Acidosis
- Uraemia
- Co-infection with viruses (abnormal ciliary function)
What causes dysregulation of inflammation: drugs
- Antacids
- Antipsychotics
- ACE inhibitors
- Glucocorticoids
- Antacids
- PPI- increases risk for pneumonia
- H2 antagonist- myelosuppression (rare, long term)
- ACE inhibitors-
associated reduced risk but only seen in observational studies with reporting bias
- Glucocorticoids-
use of inhaled corticosterois
types of URTI
- Rhinitis
- Pharyngitis
- Epiglottis
- Laryngitis
- Tracheitis
- Sinusitis
- Otitis media
URTI are most commonly caused by
viruses
- Rhinovirus
- Coronavirus
- Influenza/parainfluenza
- Respiratory syncytial virus (RSV)
Bacterial superinfection (after viral infection)
*
- Common with
- Sinusitis and otitis media–> can lead to mastoiditis, meningitis, brain abscess
Lower respiratory tract infections
- bronchitis
- pneumonia
- bronchiolitis
- empyema
- bronchiectasis
- lung abscess
- Bronchitis =
infection of the bronchi
- Pneumonia=
infection of the lung parenchyma
LRTI definittions (inflammation of the lungalveoli)
- community acquired pneumonia (CAP)
- hospital acquired pneumonia (HAP)
- venitalted acquired pneumonia (VAP)
community acquired pneumonia (CAP)
outside healthcare setting
HAP
48 hours post admission
VAP (ventilator)
48h post intubation
acute bronchitis
- Inflammation (infection *chronic bronchitis is just inflammation not infection*) of medium sized airways
- Mainly in smokers
symptoms of acute bronchitis
- Symptoms
- Cough
- Fever
- Increase SoB
- Increased sputum
investigations for acute nronchitis
- Investigations- CXR normal (don’t expect changes – in pneumonia we do)
organisms that cause acute bronchitis
- Organisms
- S.pneumoniae
- H.influenzae
- M. Cararrhalis
treatment of acute bronchitis
- Bronchodilation (symptomatic)
- Remove secretions with physiotherapy
- If bacterial antibiotics
Chronic bronchitis
NOT primarily infection
- Exacerbations have been associated with many organisms, but the role of infections remain controversial
what is penumonia
- Inflammation of the lung alveoli
- Alveoli become full of fluid and neutrophils and macrophages (fluid in lungs-dull sound and crackles on stethoscope)
pathology is the same for all types of pneumonia
- Acute inflammatory response
- Exudation of fibrin-rich fluid
- Neutrophil infiltration
- Macrophage infiltration
Lobar pneumonia–>
pneumonia involving 1 lobe
Bronchopneumonia–>
patchy
Symptoms of pneumonia
- Shortness of breath
- Coughing
- Difficulty breathing
Signs of pneumonia
ABG- hypoxic
Community acquired pneumonia causative organisms
*
- No microbiological ID made in most cases
- True prevalence difficult to establish due to use of indirect methods /mixed infections
- Typical and atypical organisms
typical causative (85%) organisms for CAP
- Strep pneumonia is commonoist
- haemophilis influenzae if COPD
atypical organisms (15%)
mycoplasma commonest
legionella- contaminated water sources
Diagnosing CAP
Clinical symptoms +imaging finding
- Clinical
- Cough (with/without sputum)
- Dyspnoea
- Pleurisy
- Fever
- Tachycardia
- Organ dysfunction (e.g. hypotension/mental status change)
- Crackles
- Bronchial breathing
- Imaging
- Consolidation/infiltrate/cavitation’s
- When to admit? Use CURB-65
Assessing severity of CAP
*
- CURB-65 score
- Confusion
- Urea >7mmol/l
- Respiratory rate>30
- Blood pressure <90 systolic <60 diastolic
- Over 65
CURB- 65 score 2
admit
- Score 2-5=
manage as severe
CAP investigations
Investigations
- FBC
- U &E
- CRP
- ABG
- Chest Xray
- Microbiological
- Sputum
- Blood culture
- Bronchoalveolar lavage fluid (BAL)
- Nose and throat swabs or NPAs (viruses)
- Urine (antigen test for legionella, pneumococcus)
- Serum (antibody test) acute and convalescent sera (usually collected at presentation and 10-14 days
management of CAP
Management
- Mild CAP- treat empirically
- Moderate CAP
- Blood culture/sputum culture
- Urinary streptococcal antigen
- Legionella +PCR
- Viral screen
- Serve CAP
- Same as moderate management + bronchoscopic specimens
Differential diagnoses for CAP
*
- Heart failure and pulmonary oedema
- Pulmonary embolism
- Atelectasis
- Aspiration/ chemical pneumonitis
- Drug reactions
- Lung cancer
- Vasculitis acute exacerbation of bronchiectasis
- Interstitial lung disease
Treatment of CAP
*
- Abx treatment
- Empirical regimes can differ in hospitals/ allergy status/ comorbidities
*
how many days of Abx for mild CAP
5-7 days
how many days of Abx for severe CAP
7-10 days
which type of Abx for mild-moderate CAP
- amoxicillin
- or doxycyclin or erythromycin
which type of Abx for moderate-severe CAP
needing hospital admission
- co-amoxiclav and clarithromycin
give amoxicillin because
commonest cause is S.pneumoniae
Complications of CAP
*
- Initial infection progression
- Empyema- infection of pleural cavity
- Lung abscess
- Bacteraemia
- Non- resolving CAP
- Delayed clinical response
- Closed space infections
- Bronchial obstruction e.g. a tumour
- Subacute chronic CAP (TB/Fungal)
- Incorrect initial diagnosis
causative organisms of hospital acquired pneumonia
- S.aureus
- MRSA
- enterobacteriaciae (E.coli and klebsiella spp_
- Pseudomonas spp
- Fungi (candida)
Management of HAP
- Cover S.aureus and gram negative enteric bacilli (e.g. klebsiella) + typical/atypical pathogens
- Co-amoxiclav
- Pseudomonas risk
- Antipseudomonal beta lactam or anti-pseudomonal fluoroquinolone (ciprofloxacin)
- MRSA risk- vancomycin/linezolid
first line treatment for HAP
co-amoxiclav
second line treatment of HAP
piperacillin or meropenem
Aspiration pneumonia
*
Aspiration of exogenous material or endogenous secretions into the resp tract
Aspiration pneumonia most common in
- Common in pts with neurological dysphagia
- Strokes
- Epilepsy
- Alcoholics
- Drowning
- At risk groups
- Nursing home residents and drug overdose
what sort of infections can aspiration pneumonias be
- Mixed infection e.g. viridians streptococci and anaerobes
- Moderate to severe aspiration pneumonia treated with
Co-amoxiclav (broad spectrum)
Immunosuppression and LRTI
- HIV
- Pneumocystis jirovecci
- TB
- Atypical mycobacteria
- Neutropenia
- Fungi e.g. aspergillus spp
- Bone marrow transplant: cytomegaly virus
- Splenectomy: encapsulated organism e.g. Pneumonia, H. influenzae, malaria
prevention of pneumonia
- immunisation
- chemoprophylaxis
- smoking advice
- Immunisation
- Flu vaccine- given to high risk pts
- Pneumococcal vaccine- every 5 years
chemoprophylaxis e.g.
