Respiratory Tract Infections 2 Flashcards
1
Q
What is the definition of pneumonia?
A
inflammation of the substance of the lungs
2
Q
Describe pneumonia in children and adults
A
Children:
- mainly viral
- neonates can develop it from chlamydia trachomatis from their mother during birth
Adults:
- mainly bacterial
- aetiology varies with age, underlying disease, occupational and geographical risk factors
3
Q
What are the common causes of viral pneumonia?
A
- influenza virus
- measles
- coronavirus
- parainfluenza virus
- respiratory syncytial virus (RSV)
- cytomegalovirus (CMV)
- adenovirus
4
Q
What are the common causes of bacterial pneumonia?
A
- streptococcus pneumoniae
- mycobacterium tuberculosis
- haemophilus influenzae
- pseudomonas aeruginosa
- staphylococcus aureus
5
Q
What is atypical pneumonia and the common causes of this?
A
- failure to respond to treatment
- mycoplasma pneumoniae
- legionella pneumophilia
- chlamydia pneumoniae
- coxiella burnetii
6
Q
What are the different anatomical classifications of pneumonia?
A
- lobar pneumonia: involvement of distinct region of lung
- bronchopneumonia:
- diffuse, patchy consolidation
- associated with bronchi and bronchioles
- interstitial pneumonia:
- invasion of lung interstitium
- usually viral
- necrotising pneumonia: lung abscesses and destruction of parenchyma
7
Q
Describe the early and following clinical features of streptococcus pneumoniae
A
initially:
- abrupt onset
- rigors
- fever
- malaise
- tachycardia
- dry cough
followed by:
- productive cough with rusty sputum
- spiky temperature
- lobular consolidation
8
Q
Describe the clinical features of mycoplasma pneumoniae
A
- fever
- dry cough
- dyspnoea
- lymphadenopathy
9
Q
What are the clinical features of haemophilus influenzae?
A
- mainly occurs in children
- consolidation or patchy bronchopneumonia
- persistent purulent sputum and malaise
10
Q
What causes Leigonnaire’s disease and what is it?
A
- legionella pneumophila
- gram negative bacillus that secretes protease causing lung damage
- transmitted by aerosol (but not person-person)
- severe systemic infection with pneumonia
11
Q
What are the clinical features of legionella pneumophila?
A
- tachypnoea
- purulent sputum
- CXR shows consolidation
12
Q
How would you diagnose legionnaire’s disease in the lab?
A
- gram stain sputum
- recognition of antigen with serotype-specific fluorescent antibody
- culture of legionella on cystine yeast extract agar
- detection of antigen in urine
13
Q
What are the clinical features and complications of mealses?
A
clinical features:
- fever
- runny nose
- Koplik’s spots
- characteristic rash
complications:
- neurological complications
- can cause ‘giant cell’ (Hect’s) pneumonia in immunocompromised - fatal
14
Q
What are the important features of the measles virus?
A
- paramyxovirus
- spread by aerosol
- affects multi-system
- replicates in LRT
- incubation 10-14 days
15
Q
How would you diagnose, treat and prevent measles?
A
diagnosis:
- serology for measles- specific IgM
- virus isolation
- virus RNA detection
treatment:
- if severe, ribavirin
- antibiotics for secondary bacterial infections
prevention:
- immunisation with highly effective, live, attenuated MMR vaccine
16
Q
What are the risk factors of pneumonia?
A
- bird contact (c. psitacci)
- travel, air conditioning (L. pneumophila)
- cystic fibrosis
- immigration (pseudomonas)
- farming (M. tuberculosis)
- recent influenza (coxiella burnetti, S. pneumoniae, S. aureus)
17
Q
What are the symptoms of pneumonia?
A
- cough
- breathlessness
- sharp chest pain
- purulent sputum
18
Q
What are the clinical signs of pneumonia?
A
- pyrexia
- purulent sputum
- rapid respiration
- signs of consolidation
- shock
- cyanosis
19
Q
Describe the process of diagnosing pneumonia
A
- history
- examination
- radiology
- sputum
- serology
- histopathology
20
Q
Describe a CURB score
A
- used to assess severity of pneumonia
- 5 features each worth 1 point
- C: confusion of new onset (AMTS of 8 or less)
- U: blood urea greater than 7 mmol/l
- R: respiratory rate of 30 breaths/min or more
- B: blood pressure less than 90mmHg systolic/diastolic 60mmHg or less
- age 65 or more
21
Q
CURB 0
A
- low severity
- home treatment
- antibiotics (amoxicillin/doxycycline)
22
Q
CURB 1-2
A
- moderate severity
- consider hospital referral
- microbiological investigations
- antibiotics given (amoxicillin/doxycyline)
23
Q
CURB 3-4
A
- urgent hospital admission
- empirical antibiotics if life-threatening (co-amoxiclav and clarithromycin)
- microbiological investigations
- urgent senior review
- if 4-5: consider transfer to critical care unit
24
Q
Define endemic, epidemic and pandemic
A
- endemic: present in community at all times, low to medium frequency at steady-state
- epidemic: sudden severe outbreak within region or group
- pandemic: occurs when epidemic becomes widespread and affects whole region/continent/world
25
Describe the features of the influenza virus
- orthomyxovirus
- single stranded RNA
- segmented
3 types:
A: epidemics/pandemics, animal reservoir
B: epidemics, no animal hosts
C: minor respiratory illness
26
What are the type-specific antigens on the surface of the influenza virus?
- haemagglutinin (H)
- neuaminidase (N)
- reassortment gives rise to new combinations of H and N antigens
27
What are the different genetic changes that the influenza virus undergoes during spread through the host?
Antigenic drift:
- point mutations in H and N antigens constantly
- allows virus to multiply in individuals with immunity to preceding strains
- new sub-type can affect community
- occurs with all types
Antigenic shift:
- sudden major change based on recombination between 2 different virus strains when they infect same cell
- produces virus with novel surface glycoproteins
- new strain can spread through previously immune populations (new pandemic)
28
What things can risk a pandemic?
- antigenic shift
- if most people have no immunity
- if attack rate is high - spreads rapidly
- mortality can be high
29
What virus causes swine flu and describe its infection
- H1N1 virus
- many older people had been infected with older virus in childhood
- vaccine contained H1N1 components
- infection limited to people under 40
- attack rate high but mortality low because many had degree of immunity
30
What is the diagnosis and treatment of influenza?
diagnosis:
- nasopharyngeal aspirate
* direct immunofluorescence
* culture
* NAAT detection
- serum serology
treatment:
- amatadine
- zanamavir
- oseltamivir
31
What is the management and prevention of influenza?
management:
- rest, warmth, hydration, analgesia
- antiviral treatment within 48hrs to reduce duration of fever
- antibiotics not given unless secondary bacterial infection suspected
Prevention:
- vaccine
- different strains of antigen used in anticipation of latest strain to emerge
32
Describe the influenza vaccine
- new vaccine based on predicted strains
- trivalent vaccine
- new recombination methods speeds up process of developing new vaccine
- those at risk (elderly, immunosuppressed etc) require annual vaccine
33
What is SARS?
- outbreak of severe respiratory disease with no identifiable cause
- China Nov 2002
- 10% fatality rate
34
What are the SARS symptoms?
- high fever
- cough
- shortness of breath
- CXRs consistent with pneumonia
35
How is SARS transmitted and the incubation period?
- transmitted via droplets, faeces and infected animals
| - incubation period of 2-7 days
36
How would you identify SARS-associated coronavirus?
- virus isolation in cell culture
- electron microscopy
- molecular techniques
37
What are the characteristics of the SARS-associated coronavirus?
- enveloped
- RNA virus
- characteristic halo
- receptor for spike protein is ACE2
38
What is the treatment of SARS?
- no specific anti-viral treatment:
* ribavirin
* corticosteroids
* interferons
* anti-retroviral therapies (eg. PI)
- whole inactivated virus vaccines
- recombinant vaccine
39
What things are associated with TB?
- AIDS
- increased use of immunosuppressive drugs
- decreased socio-economic conditions
- increased immigration from areas of high endemicity
- multiple drug resistance
- overcrowding and poor nutrition
40
What are the different clinical features of TB?
Primary TB:
- usually symptomless
- may be associated with cough and wheeze
- small transient pleural effusion may occur
Miliary TB:
- results from acute diffuse dissemination of bacillus
- fatal without treatment
Post-Primary TB:
- onset of symptoms over weeks/months
- malaise
- fever
- weight loss
- mucoid, purulent or blood stained sputum
- pleural effusion
41
What are the symptoms of TB?
- poor appetite
- night sweats
- weakness
- fever
- dry cough
- weight loss
- GI symptoms
42
Describe the features of mycobacterium tuberculosis and the disease itself
- neither gram positive or negative
- acid-fast bacilli
- human pathogen
- obligate anaerobe (found in well- aerated upper lobes of lungs)
- spread by inhalation of organisms from dust/aerosols
- primarily disease of lungs but can spread to other sites
43
Describe the Mantoux test
- used to detect latent TB infection
- tuberculin injected intradermally
- immune response if individual previously exposed to bacterium
- induration (palpable hardened area) measured after 48-72 hrs
44
Describe the importance of bacterial load on diagnostics
- symptoms differ at different bacterial loads
- patients present at different bacterial loads
- diagnostic tests become positive at different bacterial loads
- reducing the bacterial load can delay diagnosis
45
Describe the diagnosis methods of TB
- visualisation of acid-fast bacilli in sputum smears
- auramine:
* positive organisms fluoresce yellow
* more sensitive than Z/N for initial diagnosis as whole smear can be examined under low power magnification
* shows presence/absence
- Ziehl-Neelsen (Z/N)
* carbol fuschin stain and methylene blue counter stain
* 100 fields examined under 100x objective
* semi-quantification
46
What are the solid and liquid culture options for tuberculosis and the timing you would need to culture for?
Solid:
- Lowenstein-Jensen slopes: 6 weeks
- Middlebrook agar plates: 2-3 weeks
Liquid:
- mycobacteria growth indicator tube: 5-15 days
(* allows continuous monitoring of positive cultures)
47
How does bacteria show up in culture?
- bacterial growth measured by consumption of oxygen in media
- tubes contain fluoresence compound sensitive to presence of oxygen
- actively respiring bacteria consume oxygen from media allowing fluoresence to be detected
48
What is the treatment and prevention of TB?
treatment:
- combination therapy:
* isoniazid, rifampicin, ethambutol, pyrazinamide
* to prevent resistance
- prolonged therapy
* minimum 6 months
* eradicates slow growing organisms
prevention:
- childhood immunisation
- live attenuated BCG vaccine
- prophylaxis with isoniazid for 1 year
49
What are some examples of fungal infections?
- aspergillus fumigatus
| - pneumocystis jiroveci
50
What are some examples of parasitic infections?
- ascaris
- strongyloides
- echinococcus granulosus
