Respiratory Infections Flashcards
Classification of Pneumonia
Setting
- Community acquired
- Hospital acquired
- Ventalotor related
Give an overview of the Common Cold
- URTI
- Rhinovirus is the cause of 30-50% of colds
- Human Coronavirus cause about 10-15%
- transmission through hand contact and droplets
- IP is 2-3 days
- symptoms last 3-10 days: up to 2 weeks in 25% of patients
sore throat, nasal congestion, sneezing, mucus discharge, cough, fever
What causes the symptoms of a cold?
- Bradykinin: sore thought and nasal congestion due to vasodilation
- Sneezing mediated by trigeminal sensory nerves, stimulated by histamine
- Myeloperoxidase: cause of mucus discharge with increasing change of colour due to neutrophiles
- Cough mediated by the vagus nerve: inflammation has to extend to the larynx to trigger this
- Cytokines; a responsible for fevers
What is the difference between the flu and a cold?
- flu appears quickly whilst the cold is gradual
- affects system rather than just your nose and throat
- flu makes you feel exhausted and awful
- high fevers in the flu
- lower-RTI features seen in the flu
What are the symptoms of uncomplicated influenza?
- IP of 1-4 days
- Abrupt onset of fever and cough
- headache, cough, myalgia and malaise
- sore throat, nasal discharge
- Acutely debilitating
- Fever 38-41 degrees
What are some risk factors/ groups for influenza?
- immunosuppressed or those with chronic medical conditions
- Pregnant or 2 weeks postpartum
- Age < 27rs or >65yrs
- B 40 (obese)
What are some complications of influenza?
- primary viral pneumonia
- secondary bacterial pneumonia: super-infection on top of the viral damage
- CNS disease
- Death
Describe how an influenza virus enters and leaves a cell?
- flu haemagglutinin surface protein (H) binds sialic acids on the self cell surface glycoproteins and glycolipids in the respiratory tract
- influenza virus can now enter the cell
- Neuraminidase (N) on its cell surface allows the virus to escape by cleaving the sialic acid bonds
Explain reassortment in the influenza virus
- has a segmented genome, into 8 parts so can reassort if two viruses infect the same cell
- the Hemagglutinin (H) and the Neuraminidase (N) can re-assort themselves
- there is an antigenic shift and drift
- drift is a gradual change: more common in Influenza B
- a shift is a quick drastic change in the viral genome: more common in Influenza A
What are the options for treatment and prevention of influenza?
- active immunisation against H and N components
- hand hygiene and droplet precaution
- Tamiflu, Oseltamivir: a neuraminidase inhibitor
Explain what pneumonia including its cause and effects
Infection of the lung parenchyma ( functional tissue in the lungs, not connective tissue)
- causes alveoli inflammation
symptoms:
- Fever
- breathlessness, hypoxia
- increased respiratory rate
- cough
- sputum production
- pleuritic chest pain
can lead to sepsis if there is an overwhelming bacterial infection
How can pneumonia be diagnosed?
- infiltrates on a plain CXR
- consolidation due to alveoli and bronchioles filled with inflammatory debris
- heart borders and diaphragm obscured due to loss of solid-gas interface
- air bronchograms: air in larger bronchi outlines by surrounding consolidation
Describe this CXR
Right Upper Left Consolidation
Describe this CXR
Right Lower Lobe Consolidation
What imaging technique is this and what is it showing?
CT scan
Pneumonia
What pathogens cause community-acquired pneumonia?
- Strep. pneumoniae
- Mycoplasma pneumoniae
- Legionella pneumophila
- Haemophilus influenzae*
- Staphylococcus areas*
Give an overview of Strep. pneumoniae, including:
- Gram stain
- Risk factors
- prevention/treatment
- Gram-positive cocci
RFs
- alcoholics, respiratory disease
- smokers, hyposplenism
- CHD, HIV
- acquired in nasopharynx
- prevent with vaccine
- treat with penicillin
Give an overview of Mycoplasma pneumoniae including:
- Gram stain
- Risk factors
- diagnosis/treatment
- the most common cause of ambulatory (atypical) pneumonia
- Lacks cell wall can’t be gram stained
- usually in young patients
- extrapulmonary symptoms are common, i.e bruising elsewhere
- diagnosis by PCR of throat swab
- treatment: macrolides or tetracyclines which work on the ribosomes as there is no cel wall
Give an overview of Legionella pneumophila, including:
- Risk factors
- prevention/treatment
- can be sporadic or associated with contaminated water sources
RFs
- smoking
- chronic lung disease
Diagnosed: don’t grow on routine culture, use urinary legionella antigen
-Treatment: macrolides or quinolones
What pathogens cause healthcare-associated pneumonia?
- Escherichia coli
- Klebsiella pneumoniae*
- Pseudomonas aeruginosa*
- Staphylococcus aureus*
- Streptococcus spp.*
may be more resistant to antibiotics
What are some social risk factors for tuberculosis?
- Current EtOH misuse: more pulmonary diseases acquired
- current or hx drug misuse: higher MDR rates
- Homelessness: poorer tx completion rates
- Imprisonment: poorer outcomes
Describe the pathology and lab work of Tuberculosis
- it’s an aerobic Acid Fast Bacillus
- divides every 16-20 hrs (slow), cultured up to 56 days
- lacks a phospholipid outer membrane: acid-fast stain, weakly positive Gram stain
- Ziehl-Neelsen or auramine-rhodamine stain is used
Describe how a person is infected with TB
- Inhalation of aerosol droplets that contain bacteria.
- The initial stages of infection involve the innate immune response: recruitment of inflammatory cells to the lung.
- Bacterial dissemination to the draining lymph node,
- this causes dendritic cell presentation of bacterial antigens which leads to T cell priming and triggers an expansion of antigen-specific T cells, which are recruited to the lung.
- The recruitment of T cells, B cells, activated macrophages and other leukocytes leads to the establishment of granulomas, which can contain Mycobacterium tuberculosis
Explain the progression of TB from primary infection
