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103-theme 4 > respiratory tract infections > Flashcards

respiratory tract infections Flashcards

1
Q

what respiratory tract infections do we need to know for year one? 9

A
  • Streptococcus pneumoniae
  • Mycobacterium tuberculosis
  • Legionella pneumophila
  • Mycoplasma pneumoniae
  • Rhinovirus
  • Influenza
  • RSV
  • Parainfluenza virus
  • Coronavirus (human coronaviruses, SARS coronavirus 2)
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2
Q

describe the pathogenesis of respiratory tract infections?2

A
  • lungs are constantly exposed to particulate matter from the upper airway
  • lower airways are normally devoid of conventional pathogens
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3
Q

describe innate immunity and respiratory tract infections? 2

A
  • cilia= mucocilliary escalator removing debris and pathogens
  • alveolar macrophages= secrete antimicrobials, engulf and kill pathogens, recruit other immune cells, process and present antigens to T cells
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4
Q

describe acquired immunity and respiratory tract infections? 2

A
  • B cell/ T cell responses= essential for intracellular pathogens such as mycobacteria, viruses and fungi
  • IgA secreted by plasma cells interferes with adherence and viral assembly
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5
Q

what does macro mean? 5

A
  • heat
  • redness
  • swelling
  • pain
  • loss of function
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6
Q

what does micro mean? 2

A
  • vasodilation

- increased and inflammatory cell infiltration

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7
Q

name some infections of the upper respiratory tract? 5

A
  • rhinitis
  • sinitis
  • pharyngitis
  • laryngitis
  • tonsilitis
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8
Q

name some infections of the lower respiratory tract? 5

A
  • bronchitis
  • bronchiolitis
  • pneumonia
  • pulmonary tuberculosis
  • pulmonary abscess
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9
Q

name 3 types of respiratory viruses?

A
  • rhinovirus: common cold
  • influenza: flu
  • coronavirus: human= common cold, zoonotic= severe respiratory illness
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10
Q

describe the prevalence of the common cold? 6

A
  • 5-7 x a year in children
  • 2-3 x a year in adulthood
  • colds account for 40% of all time lost from work for sickness
  • > 200 viral subtypes associated
  • rhinovirus= most common, cause 30-50% of common colds
  • human coronaviruses cause about 10-15% of common colds
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11
Q

describe the transmission of the common cold? 2

A
  • hand contact= virus remains viable for up to 2 hours on skin or several hours on surfaces
  • droplet transmission from sneezing, coughing, breathing
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12
Q

what is the incubation period of the common cold?

A

2-3 days

lasts 3-10 days and up to 2 weeks in 25% of patients

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13
Q

what causes the symptoms of a cold? 5

A
  • bradykinin: intranasal administration of bradykinin causes a sore throat: it also causes nasal congestion due to vasodilation
  • sneezing is mediated by the stimulation of the trigeminal sensory nerves- histamine mediated
  • nasal discharge changes colour with increasing numbers of neutrophils
  • cough is mediated by the vagus nerve- inflammation has to extend to the larynx to trigger this
  • cytokines responsible for systemic symptoms such as fever
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14
Q

what are the specific features of a cold? 4

A
  • appears gradually
  • affects mainly your nose and throat
  • makes you feel unwell but you’re okay to carry on as normal
  • usually no fever
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15
Q

what are the specific features of a flu? 5

A
  • appears quickly within a few hours
  • affects more than just your nose and throat
  • makes you feel exhausted and too unwell to carry on as normal
  • high fevers
  • may have lower respiratory tract features
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16
Q

describe influenza? 6

A
  • caused by influenza A or B virus
  • occurs in outbreaks and epidemics worldwide, usually in winter season, so swaps hemispheres over the course of the year
  • incubation= 1-4 days
  • abrupt onset of fever and cough, headache, myalgia, malaise, sore throat and nasal discharge
  • acutely debilitating
  • fever=38-41
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17
Q

what are the risk groups for complications from influenza? 5

A
  • immunosuppression or chronic medical conditions
  • pregnancy
  • under 2 years old
  • over 65 years old
  • BMI>40
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18
Q

what are the complications of influenza? 4

A
  • primary viral pneumonia
  • secondary bacterial pneumonia
  • CNS disease
  • death (0.13%)
19
Q

what are the 3 problems that a virus must solve?

A
  • it must know how to replicate inside the cell
  • it must move from one infected cell to a new cell (and a new host) in order to persist in nature
  • it must develop mechanisms to evade host defences
20
Q

how does the influenza virus work? 3

A
  • haemagglutinin surface protein (H) binds to sialic acids on the cell surface glycoproteins and glycolipids in the respiratory tract
  • this allows it to enter the cell
  • neuraminidase (N) on the surface of the virus allows the virus to escape by cleaving sialic acid bonds
  • the influenza has a segmented genome (8 parts) so it can re-assort if 2 different viruses infect the cell
21
Q

what are the options for treatment and prevention of influenza?

A
  • active immunisation against haemagglutinin and neuraminidase components
  • tamiflu= a neurominidase inhibitor
  • hand hygiene and droplet precautions
22
Q

what is pneumonia? 3

A
  • infection of the lung parenchyma (functional tissue)
  • alveoli full of inflammation= blocks oxygen transfer
  • fever, breathlessness, cough, sputum production, hypoxia, increased respiratory rate, pleuritic chest pain, sepsis
23
Q

describe the radiology of pneumonia? 4

A
  • diagnosis of pneumonia requires infiltrates on plain CXR with supporting clinical features
  • consolidation- alveoli and bronchioles completely filled with inflammatory debris/ pus/ pathogens
  • heart borders or diaphragm obscured due to loss of solid-gas interface
  • air bronchograms= air in larger bronchi outlined by surrounding consolidation
24
Q

name some community-aquired pneumonia pathogens? 3

A
  • Streptococcus pneumoniae
  • Mycoplasma pneumoniae
  • Legionella pneumophila
25
Q

describe streptococcus pneumoniae? 4
risk factors? 6
prevention?
treatment?

A
  • most common organism
  • gram positive cocci
  • acquired in the nasopharynx
  • asymptomatic carriage in 40-50%
  • alcoholics, respiratory disease, smokers, hypoplenism, heart disease, HIV
  • vaccine
  • penicillin
26
Q

describe mycoplasma pneumoniae? 6

A
  • most common cause of atypical pneumonia
  • classically young patients, several weeks
  • extra-pulmonary symptoms are common
  • resistant to penicillin as it lacks a cell wall
  • diagnosed by a throat swab
  • treatment- macrolides
27
Q

describe legionella pneumophillia? 5

A
  • can occur as sporadic infection or in outbreaks associated with contaminated water
  • uncommon
  • severe life threatening infection
  • smoking and chronic lung disease are risk factors
  • diagnosed as it doesn’t grow on routine culture, urinary legionella antigen
28
Q

describe healthcare associated pneumonia? 3

A
  • new onset at least >48 hours since admission
  • hospitalised patients become colonised with hospital bacteria
  • these may be intrinsically more resistant to antibiotics, or have acquired resistance mechanisms
29
Q

describe the pathology of TB? 6

A
  • aerobic bacillus
  • divides every 16-20 hours (slow)
  • cell wall, but lacks phospholipid outer membrane
  • does not stain strongly with Gram stain
  • retains stains after treatment with acids
  • referred to as acid fast bacillus
30
Q

name 2 special strains of TB?

A
  • Ziehl- neelsen

- auramine-rhodamine

31
Q

describe the infection of TB? 4

A
  • infection is initiated by the inhalation of aerosol droplets that contain bacteria
  • the initial stages of infection are characterised by innate immune response that involve the recruitment of inflammatory cells to the lung
  • following bacterial dissemination to the draining lymph node, dendritic cell of antigen specific T cells which are recruited to the lung
  • recruitment of T cells, B cells and activated macrophages and other leukocytes leads to the establishment of granulomas which can contain MTB
32
Q

describe latent TB? 5

A
  • dormant bacilli
  • contained by host defences
  • non-infectious
  • asymptomatic
  • diagnosis by demonstrating host IR
33
Q

describe active TB? 4

A
  • actively replicating bacilli
  • may be infectious (site dependent)
  • symptomatic (site dependent)
  • diagnosis by isolating acid fast bacilli, growing MTB or PCR positive
34
Q

what is the management aim of TB? 5

A
  • cure active disease
  • reduce spread
  • prevent reactivation
  • prompt and adequate treatment
  • appropriate source isolation by contact tracing
35
Q

describe the chain of infection of SARS-COV-2? 6

A
  • Infectious agent (SARS-Cov-2)
  • Reservoir (humans and other mammals)
  • Portal of exit (coughing, talking, sneezing)
  • Mode of transmission ( droplet, aerosol and contact)
  • Portal of entry (mouth, nose and eyes)
  • Susceptible host (susceptible people)
36
Q

what are the symptoms of SARS-COV-2? 6

A
  • A new continuous dry cough
  • Fever over 37.8
  • Change or loss of sense of smell or taste
  • The frequency of nausea, vomiting, abdominal pain, headache and sore throat increased with increasing age
  • But fever and runny nose become less common with increasing age
  • More severe symptoms develop later
  • Hospital admission is usually on days 8-10
37
Q

describe the statistical outcomes of SARS-COV-2? 4

A
  • 80% have asymptomatic to moderate disease and recover without needing hospital treatment
  • 13% may get severe disease
  • 5% become critically unwell
  • Infection fatality rate is about 0.9% but varies according to age and sex
38
Q

who is the most at risk from covid? 3

A
  • The single greatest risk of mortality from COVID-19 is increasing age
  • The risk increases exponentially with age
  • 80% have of deaths have been in those ages 70 or older
39
Q

what are the risk factors for covid? 3

A
  • Those with underlying medical conditions
  • BAME
  • Age
40
Q

how can you classify severe COVID-19? 3

A
  • Admission of:
  • Oxygen sats <90%
  • Respiratory rate >30
  • Signs of severe respiratory distress
41
Q

what are the complications of COVID-19? 4

A
  • High risk of thromboembolism
  • Glycaemic issues
  • Acute kidney injury
  • Cardiac toxicity
42
Q

what is the treatment for COVID-19? 3

A
  • Supportive care
  • High flow oxygen
  • Dexamethasone
43
Q

how do we prevent COVID-19? 6

A
  • PPE
  • Ventilation
  • Reducing encounters
  • Reducing contact
  • Handwashing
  • Immunisation

103-theme 4 (19 decks)

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