Lecture 17 - Lower respiratory tract infection Flashcards
Pathogens that cause respiratory tract infections
Viridans streptococci
Fungi - candida
Less common:
- strep pneumoniae
- strep pyogenes
- haemophilus influenzae
Why are lungs not sterile?
Normal alveolar microbiota
Aspiration
Blood stream spread
Direct spread
Defences of respiratory tract
Mucous Muco-ciliary escalator Cough and sneezing Nasal hairs Tonsils - lymphoid follicles Secretory IgA and IgG Alveolar microbiota
Epithelial lining of the respiratory tract
Psuedostratified ciliated columnar cells
Typical infection pathophysiology
- Alveolar macrophages fail to stop pathogens from invading and multiplying
- Activated macrophages release cytokines that recruit more macrophages
- Inflammation and increased permeability as there is and increased blood supply
- Recruitment of immune cells like neutrophils and lymphocytes
- Damage to lung tissue
Typical infection effects systematically
- Inflammatory mediators like cytokines and chemokines are released into the systemic circulation
- Bone marrow releases neutrophils, increased heart rate and higher temperature causing pyrexia
- Dysregulation can cause tissue and organ injury
What causes dysregulation
Pathogen
Host factors
Drugs
Virulence factors of pathogens
Chlamydia pneumoniae - ciliotatic factor
Mycoplasma pneumoniae- shear off cilia
Strep pnuemoniae and neisseria meningitides - split IgA
Pneumoccocus - capsule inhibits phagocytosis
Mycobacterium/ Leigonella - resistant to phagocytosis
Host factors
Age - older than 65 Smoking - abnormal ciliary function Chronic lung disease Aspiration Immunocompromised - DM/HIV Co-infection
Drugs that increase the risk of pneumonia
Antacids - PPI - increased risk of pnuemonia
Upper respiratory tract infection
Laryngitis Pharyngitis Sinusitis Rhinitis Epiglottitis
Lower respiratort tract infections
Bronchitis
Pneumonia
Lung abscesses
Bronchiectasis
Acute bronchitis pathophysiology, symptoms, treatment, pathogen
Inflammation of small and medium sized airways
Mainly in smokers
Symptoms:
- Cough
- Fever
- Sputum production
- SOB
Organisms:
- Strep pneumoniae
- Haemophilus influenzae
- Maroxella catarrhalis
Treatment:
Bronchodilation
Physiotherapy
+/- Antibiotics
Pneumonia
Acute inflammatory response to infection
Exudate released into lumen which can cause obstruction
Neutrophil and macrophage infiltration
Types of pneumoniae
Lobar pnuemoniae
- involves whole lobe
- consolidation of whole lobe
Bronchopneumonia
- patchy and diffuse
- affect the bronchioles and alveoli
Atypical/interstitial
- affects the interstitium outside the alveoli
Signs of pneumonia
Percussion: Dull resonance over affected area due to consolidation
Auscultation:
- Crackles
- tactile vocal fremitus - sound louder when saying phrases e.g. 99 as sounds travels faster through fluid
- bronchial breathing
CXR: consolidation
- patchy
Typical organisms that cause pneumniae
Streptococcus pnuemoniae Maroxella Catarrahalis Haemophilus Influenzae Klebsiella pnuemonia Staph aureus Group A Strep pyogenes
Fungi
- cryptococcus
- pneumocystis jiroveci - risk for immunocompromised individuals as opportunistic
Atypical organism of pneumonia
Mycoplasma pneumoniae
Legionella pneumophila - contaminated water sources
Chlamydophila pneumoniae
Symptoms of pneumonia
Cough Productive cough Dyspnoea Pluerisy - sharp chest pain fever
CURB 65
Confusion Urea in blood over 7 mmol/L Resp rate over 30 Blood pressure - systolic Over 65 yrs old
Investigations for pneumoniae
FBC U+E CRP ABG CXR cytology of sputum
Treatment
Antibiotics
Oral fluid intake
Analgesia
Mild pneumonia antibiotics
Amoxacillin
or doxycycline/ erythromycin/ clarithromycin
Moderate to sever antibiotics
Hospitalisation
Co-amoxiclav
Clarithromycin
Doxcycline
Atypical pneumonia antibiotics
Macrolides
erythromycin
clarithromycin
Complications of pneumonia
Lung abscesses
Empyema - pockets of pus inside pleural space
Bacteraemia
First line hospital aquired pneumonia
Co-amoxiclav
Aspiration pneumonia
Aspiration of exogenous or endogenous secretions in the respiratory tract Decreased gag reflex due to: - drug overdose - epilepsy - dysphagia - alcohol abuse
Pathogens causing aspiration pneumoniae
Viridans streptococci
Anaerobes
Presentation of atypical pneumonia
Cause vague symptoms like fatigue and regional
Community acquired pneumonia
Person gets ill outside of a hospital of healthcare setting
Hospital acquired pneumonia
Nosocomial
Patient is already sick in hospital
More serious as
- patient has a weakened immune system as already sick
- microbes in the hospital are more resistant to antibiotics e.g. MRSA
Stages of lobar pneumonia
- Congestion (day 1 and 2)
- blood vessels and alveoli fill with excess fluid - Red hepatisation (day 3 and 4)
- exudate (RBCs, Neutrophils and fibrin) fill air spaces making them more solid
- liver like appearance - Grey hepatisation (Day 3 to 7)
- still firm
- colour change as RBCs break down - Resolution (Day 8 to 3 weeks)
- exudate is digested by enzymes, ingested by macrophages or coughed up
