Infection Flashcards
Definition of pneumonia
An inflammation of the substance of the lungs/parenchyma in which the air sacs fill with pus and may become solid
What is protection against pathogenic bacteria provided by?
Colonisation
- commensal flora and colonisation resistance
Swallowing
- enruological + anatomical factors
Lung anatomy
- mucociliary escalator
- cough reflex
Immunity (innate and adaptive)
Symptoms of pneumonia
pyrexia (fever)
Resp symptoms: cough sputum chest pain (pleurisy) dyspnoea
Precipitating factors for pneumonia
infants + elderly underlying lung disease immunocompromised impaired swallow congestive HF alcoholics + drug users
Epidemiology of legionella pneumophila (a cause of CAP)
summer, water tanks, travel related (50%)
Epidemiology of chlamydophila pneumoniae
often older adults, sometimes closed outbreaks, longer duration of symptoms
If someone had contact with sick birds, what would you suspect?
chlamydophila psittaci
If someone had had contact with farm animals, esp sheep, what would you predict
Coxiella burnetti
Pathogenesis of pneumonia
Bacteria ‘translocate’ to the normally sterile distal airway
‘overwhelm’ resident host defence
‘develop and inflammatory response’
‘resolution phase’ when bacteria cleared
When would severe disease occur? (pathogenesis of pneumonia)
excessive inflammation
lung injury
and/or failure to resolve without lung damage
What does rusty sputum suggest?
S. pneumoniae
Pneumonia signs
Abnormal vital signs
Signs of lung consolidation on percussion + auscultation
+/- hypoxia + signs of resp failure
Investigations for pneumonia
WCC - aids Dx and is a marker for severity
CXR
Sputum - Gram stain, culture + sensitivity tests
Serology - for viruses + atypical organisms
Pulse oximetry (severity) +/- ABG (define RF)
CRP
Urinary antigen - legionella +pneumococcal antigens
What would CXR with upper lobe cavity suggest?
K. pneumoniae
but must exclude TB
What would a CXR with multilobal consolidated area suggest?
S. pneumoniae,
S. aureus
Legionella sp.
Assessment of severity in pneumonia
CURB65
Predicts mortality
confusion, urea, resp rate, BP, age
Tx for mild severity pneumonia in community
amoxicillin
Tx for moderate severity pneumonia
amoxicillin + clarithromycin
Antibiotic Tx severe pneumonia
co-amoxiclav + clarithromycin
or
cefuroxime + clarithromycin
Whats the duration to classify as severe pneumonia?
7-10 days
Specific Tx for severe legionella sp pneumonia?
Ensure fluoroquinolone in regimen either alone or with clarithromycin
Prevention of pneumonia
Polysaccharide pneumococcal vaccine
Influenza vaccine to those >65 yrs, Immunocompromised or with co-morbidities
Smoking cessation
Complications of pneumonia
lung abscess
empyema (presence of pus in the pleural cavity)
What can cause pus in the pleural cavity? and whats the presentation?
- rupture of lung access
- bacterial spread of severe pneumonia
Px: very ill, high fever and neutrophil leucocytosis
What’s a lung abscess?
From localised suppuration of the lung with cavity formation, often with a fluid level on CXR
What causes a lung abscess?
Complicating pneumonia
Secondary to bronchial obstruction
From septic emboli from a focus elsewhere
Secondary to infarction
What needs to happen promptly to an empyema?
Drainage by catheter insertion or chest tube placement
Antibiotics for empyema?
co-amoxicalv
Who are lung abscesses seen in and whats the Tx?
aspiration, alcoholics and those with poor dentition
prolonged antibiotics for up to 6 wks
may need surgical drainage
What would you suspect an elderly in patient with new fever, purulent secretions, radiological infiltrates, leukocytosis and increasing O2 requirements to have?
HAP
(acquired at least 2 days after admission)
could be Staph. aureus including methicillin resistant
What’s the m. tuberculosis complex?
m. tuberculosis and m. bovis
aerobic, non-spore forming non-motile bacteria with high content of high MW lipids in its cell wall
what is post-primary Tb?
all forms of tb that develop after the 1st few weeks of the primary infection when immunity to the mycobacterium has developed
What is in the primary focus in TB characterised by?
exudation + infiltration with neutrophil granulocytes
What’s a Gohn complex in TB?
In primary infection
The gohn focus (typical granulotamous lesions formed by macrophages), as well as caseous lesions in regional lymph nodes
what is maxillary tb as a result of?
acute dissemination of tubercle bacilli via the bloodstream
how is tb spread?
in aerosol from infected individual’s lung to another lung
or via spitting or sneezing on plates or hands
Whats the natural history for most cases of TB?
the immune response enables the primary complex to encapsulate + contain the organism forever
lesions become fibrosic + calcify but may continue to house viable but dormant organisms for decades
What factors would favour Tb disease (not infection) to develop?
age
immunosuppression
malnutrition
intensity of exposure
reinfection/new exposure
Post-primary TB - whats this due to?
usually endogenous reactivation but also reinfection
Where do secondary TB lesions develop?
in the regional lymph nodes
What forms the primary complex?
granuloma (formed by macrophages) + lymphatics + lymph nodes
If primary disease isn’t contained, what happens (TB)?
there is haematogenous dissemination, often leads to serious pulmonary disease
what is post primary disease?
reactivation after a dormant phase
systemic features of active TB
weight loss* low grade fever anorexia night sweats* malaise
Symptoms of pulmonary TB
chest pain, dyspnoea
upper lobe consolidation: dull apex with bronchial breathing
compression by LN: collapse, cough etc.
Ix TB
CXR: patchy or nodular shadows in the upper zones
Sputum/bronchoscopy with washings
LP: to examine CSF for evidence of infection in all cases of military TB
contact tracing for tb?
report all cases to the local Public Health Authority
Drug treatment for TB
DOT (directly observed therapy)
rifampicin
isoniazid
pyrazinamide
ethambutol
what tb drug has a possible side effect of optic neuritis?
ethambutol
what drug stains body secretions and urine pink (TB)
rifampicin
whats the BCG vaccine?
a bovine strain of M. tuberculosis which has lost its virulence after growth in the lab for many years
immunisation produces cellular immunity and a positive mantoux test
rifampicin mechanism of action
inhibits bacterial DNA-dependent RNA synthesis by inhibiting bacterial DNA-dependent RNA polymerase.
Pharyngitis aetiology
viral: rhinovirus, adenovirus
glandular fever EBV
Acute HIV infection
streptococcus pyogenes,
what viruses cause croup?
parainfluenza viruses
what is sinusitis usually caused by?
viral infection
what do rhinoviruses cause?
rhinoviruses: common cold, bronchitis, sinusitis
what do coronaviruses cause?
colds but occasionally severe respiratory illnesses
what do adenoviruses cause?
URT infection, pharyngitis, bronchitis, occasional pneumonia
emerging respiratory virus infections
SARS
Middle East Respiratory Syndrome novel Coronavirus
Avian influenze
What URT infection does haemophilus influenza type B (Hib) cause?
acute epiglottitis
Whats another name for acute laryngo-treacheobronchitis?
croup!
mainly due to parainfluenza viruses
what does respiratory syncytial virus cause?
bronchiolitis
