Respiratory Infection Flashcards
What are the risk factors for acute respiratory infection?
Risk factors for acute respiratory infection include poor nutrition, young children, elderly, poverty and poor access to basic amenities, smoke pollution, and overcrowding. Immunocompromised individuals, such as those with HIV, are also at increased risk.
What is the pathogenesis of acute respiratory infection?
The lower airways are usually devoid of conventional pathogens, and the innate immune system, consisting of cilia, mucociliary escalator (MCE), and alveolar macrophages, works to remove debris and pathogens. Acquired immunity through B cell/T cell responses is essential for intracellular pathogens, such as mycobacteria, viruses, and fungi. IgA secreted by plasma cells interferes with adherence and viral assembly.
What is the response to infection in acute respiratory infection?
Inflammation is the body’s response to insult, with macroscopic symptoms including redness, swelling, heat, pain, and loss of function, and microscopic symptoms including vasodilation, increased vascular permeability, and inflammatory cell infiltration. The response can be acute or chronic.
What are some commensals found in the respiratory tract?
Some commensals found in the respiratory tract include Staphylococcus aureus and Streptococcus pneumoniae in the mouth, S. pneumoniae, Haemophilus influenzae, Staphylococcus aureus (MRSA), and rhinovirus in the sinus/nasal passage, and MRSA in the throat.
What are some infections of the upper respiratory tract?
Some infections of the upper respiratory tract are colds caused by rhinovirus and tonsillitis caused by Streptococcus Group A
What are some infections of the lower respiratory tract?
Some infections of the lower respiratory tract are bronchitis caused by Streptococcus pneumoniae and Haemophilus influenzae, bronchiolitis caused by respiratory syncytial virus, and pneumonia caused by Streptococcus pneumoniae, Haemophilus influenzae, Legionella pneumophila, and Mycoplasma pneumoniae.
What are some viral infections of the respiratory tract?
Some viral infections of the respiratory tract are influenza, rhinovirus, and respiratory syncytial virus (RSV).
What causes the symptoms of a cold?
The symptoms of a cold are caused by various factors. Vasodilation caused by bradykinin can lead to a sore throat and nasal congestion. Sneezing is mediated by the trigeminal sensory nerves, while nasal discharge (snot) changes color with increasing numbers of neutrophils due to myeloperoxidase. Cough is mediated by the vagus nerve, and cytokines are responsible for systemic symptoms such as fever.
what are features of the cold
Appears gradually
affects mainly nose and throat
feel unwell but able to work
no fever
what are the features of influenza
appears quickly, within hour
affects whole body
Coryzal symptoms exhaustion, myalgia, fever
unable to work
What causes influenza?
Influenza is caused by the Influenza A or B virus.
What are the symptoms of uncomplicated influenza?
The symptoms of uncomplicated influenza include an abrupt onset of fever, cough, headache, myalgia and malaise, sore throat, and nasal discharge.
What are the risk factors for influenza?
Risk factors for influenza include immunosuppression, chronic medical conditions such as diabetes, COPD, or asthma, pregnancy or 2 weeks postpartum, age less than 2 years or over 65 years, and BMI over 40.
What are some of the complications of influenza?
Complications of influenza include primary viral pneumonia, secondary bacterial pneumonia, CNS disease, and death.
what is the stages of viral infection within the cell
attachment- virus binds to the receptor on the host surface
penetration- viral nucleic acid enters the cell
synthesis of new components- viral nucleic acid takes over control of cell metabolism and is replicated
assembly- whole virus particles are made
release- lysis or slow leakage of the host cell wall
What are the challenges for a virus?
Replication inside the host cell
Transmission from one infected cell to another in a new host
Develop mechanisms to evade host defences
What is the role of haemagglutinin in the influenza virus?
The influenza virus haemagglutinin surface protein (H) binds sialic acid receptors on host cells in the respiratory tract. This allows the influenza virus to enter the cell.
What is the role of neuraminidase in the influenza virus?
The neuraminidase (N) on the surface of the influenza virus allows the virus to escape by cleaving sialic acid bonds – otherwise the escaping virions all clump together.
How is the influenza virus genome organized?
The influenza virus has a segmented genome (8 parts) so can reassort if 2 different viruses infect the same cell.
What are the options for treatment and prevention of influenza?
Prevention includes hand hygiene and droplet precautions, annual immunization against H1N1, and treatment options include a neuraminidase inhibitor such as Tamiflu (oseltamivir), which blocks the enzyme neuraminidase and prevents the replication of the virus.
What is pneumonia?
Pneumonia is an infection of the lung parenchyma.
What are the symptoms of pneumonia?
The symptoms of pneumonia include fever, breathlessness, cough, sputum production, pleuritic chest pain.
What are the signs of pneumonia?
The signs of pneumonia include tachypnoea (increased respiratory rate), reduced chest expansion and breath sounds, consolidation (dullness on percussion and increased tactile vocal resonance and vocal resonance) and bronchial breathing.
What is the radiological diagnosis of pneumonia?
Diagnosis of pneumonia requires infiltrates on a plain CXR with supporting clinical features. Features include consolidation, obscured heart borders or diaphragm, air bronchograms, lobar pneumonia, and bronchopneumonia.
What are the different classifications of pneumonia?
The different classifications of pneumonia include Community Acquired Pneumonia (CAP), Hospital Acquired Pneumonia (HAP), Healthcare Associated Pneumonia, Ventilator Associated Pneumonia (VAP), and Aspiration Pneumonia.
What are the symptoms of CAP in young and immunocompetent patients?
The symptoms of CAP in young and immunocompetent patients include productive cough, green/rusty brown sputum, fever, rigors, pleuritic chest pain, and dyspnoea.
What are the symptoms of CAP in the elderly or immunocompromised?
The symptoms of CAP in the elderly or immunocompromised may include confusion and an absence of typical symptoms, as well as presenting with generally unwell, off food, and dehydrated.
What are the common bacteria causing CAP?
streptococcus pneumoniae
Haemophilus influenzae
Mycoplasma pneumoniae
Legionella pneumophila
Staphylococcus aureus
Respiratory viruses probably responsible for ~1/3
Pneumocystis jiroveci (PCP) in cell-mediated immunodeficiency
Aspergillus fumigatus (fungal pneumonia)
What is the commonest organism causing CAP?
Streptococcus pneumoniae
What are the risk factors for Streptococcus pneumoniae?
Alcoholics, respiratory disease, smokers, hyposplenism, chronic heart disease
HIV – 50- to 100-fold increase in invasive pneumococcal disease in HIV+
How is Streptococcus pneumoniae acquired?
Acquired in nasopharynx
Asymptomatic carriage in 40-50%
smokers>non-smokers
How is Streptococcus pneumoniae diagnosed and treated?
Pneumococcal antigen in urine
Prevention – vaccine
Treatment – amoxicillin or clarithromycin or co-amoxiclav in severe CAP
What is Haemophilus influenzae?
Gram negative anaerobe
Who is most affected by Haemophilus influenzae pneumonia?
Affects those with co-morbidities
What are the complications of Haemophilus influenzae pneumonia?
Complications common (empyema)
What is the mortality rate for Haemophilus influenzae pneumonia in adults?
Mortality in adults 12-29%
How is Haemophilus influenzae pneumonia treated?
Treatment: Tetracycline eg Doxycycline
What is Mycoplasma pneumonia?
Lacks cell wall
resistant to penicillin
cannot grow on normal lab plates
What are the symptoms of Mycoplasma pneumonia?
Classically young patient, vague constitutional upset, several weeks
Extrapulmonary symptoms very common
How is Mycoplasma pneumonia diagnosed and treated?
Diagnosis by PCR of throat swab
Treatment: macrolides or tetracyclines
What is Legionella pneumophilia?
Can occur as sporadic infection or in outbreaks associated with a contaminated water source (consider travel and nosocomial acquisition)
How common is Legionella pneumophilia and who is at risk?
Uncommon – 350 cases/year
RFs= smoking and chronic lung disease
How is Legionella pneumophilia diagnosed and treated?
Don’t grow on routine culture – need special conditions, and longer
Urinary legionella antigen
Treatment: macrolides or quinolones
What scoring systems are used to assess the severity of Community Acquired Pneumonia (CAP)?
The CRB-65 or CURB-65 score should be calculated.
What is included in the CRB/CURB score?
C = confusion, R = respiratory rate, B = blood pressure, U = urea.
What is the mortality rate for CAP?
Mortality can range from 2% to 40%.
What is hospital-acquired pneumonia (HAP)?
Pneumonia that develops more than 48 hours after admission to the hospital in someone who did not have pneumonia on admission.
What are some risk factors for HAP?
Elderly, co-morbidities, and immunocompromised.
What are some organisms that cause HAP?
Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, and MRSA.
Is multi-drug resistance common in HAP?
yes
What type of respiratory failure can HAP often develop?
Type 1 Respiratory Failure.
What is ventilator-associated pneumonia (VAP)?
A type of HAP that develops in 50% of patients who are intubated and ventilated, either through micro-aspiration or through contamination of the ventilator equipment.
What are some risk factors for VAP?
Hospitalization for more than 48 hours, antibiotic therapy in the last 6 months, underlying lung disease, immunosuppression, and significant other co-morbidities.
Are the organisms that cause HAP the same as the ones that cause VAP?
yes
Is multi-drug resistance common in VAP?
yes
What is the morbidity and mortality like for VAP?
High morbidity and mortality.
What is empyema?
Infection (pus) in the pleural space.
What are some risk factors for empyema?
Elderly, immunocompromised, alcoholics, and diabetes mellitus.
How is empyema diagnosed?
Imaging (CXR, thoracic ultrasound, CT thorax), pleural aspiration (pus, low pH, exudate, bacteria).
What is the management for empyema?
Long course of antibiotics, intrapleural fibrinolytic drugs (e.g., streptokinase), pleural drainage, and surgery (Video-assisted thoracoscopy = VATS).
What are some risk factors for opportunistic infections?
HIV.
What is an example of an opportunistic infection?
Pneumocystis jiroveci (PCP).
What is Pneumocystis jiroveci?
Pneumocystis jiroveci is an atypical fungus (previously a protozoan) that is ubiquitous in the environment.
How is Pneumocystis jiroveci transmitted?
Pneumocystis jiroveci is transmitted via the airborne route of infection and person-to-person spread.
What are the symptoms of Pneumocystis jiroveci?
The symptoms of Pneumocystis jiroveci include cough, severe breathlessness, hypoxia, and bilateral, interstitial ground glass shadowing on a chest X-ray in a bat’s wing appearance.
What is the treatment for Pneumocystis jiroveci?
The treatment for Pneumocystis jiroveci is Co-trimoxazole.
What are the symptoms of COVID-19?
The symptoms of COVID-19 include fever, cough, dyspnea, loss of sense of smell and taste, headaches, myalgia, and profound fatigue.
What is the clinical manifestation of COVID-19?
COVID-19 can lead to severe LRTI and interstitial pneumonia.
What is the incubation period of COVID-19?
The incubation period of COVID-19 is 6.4 days.
What percentage of people with COVID-19 are asymptomatic?
Approximately 17% of people with COVID-19 are asymptomatic.
What are the high-risk groups for COVID-19?
The high-risk groups for COVID-19 include the elderly (>80), those with high BMI, BAME, and comorbidities.
What are the management options for COVID-19?
The management options for COVID-19 include supportive care, such as oxygen therapy (high flow O2, CPAP, intubation, and ventilation), and specific treatments such as Dexamethasone, Remdesivir, and Tocilizumab. Prevention and control measures include face masks, hand hygiene, test, track, and trace, self-isolation, and vaccination.
