Lower Respiratory Tract Infections Flashcards
What is laryngitis? Tracheitis?
- an infection of the larynx and trachea
- adults: can cause hoarseness and a burning pain
- children: have a narrow airway that is easily obstructed, making it very dangerous for them and potentially leading to hospitalization
What is the most common cause of laryngitis or tracheitis?
- parainfluenza virus, RSV, influenza or adenovirus
What bacteria usually cause the laryngitis/tracheitis infection?
- group A streptococci
- H. influenzae
What bacteria typically causes diphtheria?
- corynebacterium diphtheria
What is the prevalence of the diphtheria in the human population?
- many of us carry the bacteria diphtheria in our mouth, but we are not containing the pathogenic strain- we do not have the viral genome contained within it, which means that it is not pathogenic
- bacteria encodes for a toxin- this is what makes it pathogenic (the AB protein is what makes the protein viral)
What causes the dangerous accumulation of film in the back of the throat that makes it hard for people to breath?
- when the bacteria has an AB protein in it, it is viral- the AB protein inhibits protein synthesis and causes cell death
- the dead cells can then accumulate in the airway and can block the airway completely
- the dead mass of cells is very tightly attached to the live cells of the tissue, so it has to be surgically removed
- it is the virus that is responsible for the production of the toxin
What are some of the complications associated with diphtheria?
- myocarditis
- polyneuritis (paralysis of the soft palate that causes regurgitation of liquids)
- all of these are caused because the toxin from the diphtheria is absorbed into the lymph nodes and the blood
What is the treatment required for diphtheria?
- treatment is immediate, since this is a life threatening condition
- needs to be treated with an antitoxin (horse serum) and antibiotics
What vaccine vaccinates against diphtheria?
- combination of pertussis, tetanus, polio and H. influenza B
What bacteria is known to cause pertussis? (whooping cough)
- bordetella pertussis and parapertussis
How is pertussis spread?
- by airborne droplets - it is a disease that is confined to humans
- especially affects infants and young children
The organism attaches to and multiplies within the _________, and does not spread to deeper structures in the lungs
ciliated respiratory mucosa
What is the clinical presentation of pertussis in a child?
- early phase: viral upper respiratory tract infection
- fever is uncommon, showing paroxysms of coughing
- this is the sum of several toxins
- dry, unproductive cough
Bordatella pertussis infections are associated with the production of various _____
toxic factors
What are the 3 toxins that cause pertussis?
- pertussis toxin (A-B type- A-subunit: ADP ribosyl transferase that catalyzes transfer of ADP-ribose from NAD to host cell proteins, affects signal transduction)
- adenylate cyclase (enters neutrophils, causes increased cAMP which inhibits their chemotaxis, phagocytosis and bactericidal killing ability)
- tracheal toxin (kills tracheal cells)
What are the most common complications of pertussis?
- pneumonia as a secondary infection, which can potentially cause alveolar rupture
- CNS infections such as seizures
What are the 3 stages of a pertussis infection?
- Catarrhal (mild cold, runny nose, mild cough)
- can last several weeks - Paroxysmal (severe coughing begin)
- 15-25 paroxysmal fits/ 24 hours -> vomiting and whooping - Convalescent (slow decrease of symptoms -> 4 weeks after infection)
What does the pertussis vaccine consist of?
- acellular vaccines
- pertussis toxoid + bacterial components (filamentous haemagglutinin and fimbrae)
Describe acute bronchitis?
- inflammation of the tracheobronchial tree
- often viral in nature, but can be bacterial
What viruses are known to cause acute bronchitis?
- rhinovirus, coronavirus, influenza virus, adenovirus
What bacteria typically cause pertussis?
- bordatella pertussis, B. parapertussis, mycoplasma pneumoniae, chlamydophila pneumoniae
Is there a time of the year that bronchitis peaks?
- peaks in winter
shows cough, fever and variable amounts of sputum
Acute bronchitis usually follows an _______
upper respiratory tract infection
The spread of acute bronchitis is usually caused from damage to the _____ epithelial cells by the same viral pathogens
respiratory
What are the main complications associated with acute bronchitis ?
- secondary bacterial infections
-potentially pneumonia
S. pneumoniae or H. influenzae
_____ is the primary cause of bronchiolitis and pneumonia in infants under 2 years old
RSV
Respiratory Syncytial Virus is spread via transmission by ____
droplets
When an RSV infection occurs, the ____ narrow, causing difficulty in breathing
bronchioles
Why is an RSV infection so dangerous in young children?
- it is inhaled and there is an established infection in the nasopharynx as well as the lower respiratory tract, causing bronchiolitis or pneumonia
- his can lead to cough, fast respiratory rate and even cyanosis
- in older children however the mortality rate is better, since the infection does no go as far down into the respiratory tract
What is the animal host for the Sin Nombre Virus, or the new world hantavirus?
- the deer mouse
How is the Sin hombre virus transmitted from the deer mouse to humans?
- via inhalation of the SNV infected rodent feces, or from saliva or urine
What is the clinical presentation of the SNV in humans?
- flu-like symptoms, with a viral invasion of pulmonary capillary endothelium
- fluid pours into the lungs due to an increased vascular permeability
- 35% mortality rate
What are the symptoms associated with old world hantavirus?
- hemorrhagic fever and renal syndrome
Pneumonia is an inflammation of the _______
lower respiratory tract
Where does the bacteria invade in a pneumonia infection?
- invades the lungs -> from the alveolar spaces, the interstitium and the terminal bronchioles
What are the 4 routes of a pneumonia infection?
- upper airway colonization or infection that extends into the lung
- aspiration of organisms
- inhalation of airborne droplets
- seeding of lung via blood from distance site
(pneumonia is often a secondary bacterial infection)
What are the 4 different types of pneumonia?
- lobular pneumonia (distinct region of the lung)
- bronchopneumonia (diffuse patchy)
- interstitial pneumonia (invasion of the lung interstitium, viral)
- lung abscess (cavitation and destruction of the lung parenchyma)
What are the two bacteria that pneumonia is likely caused by?
- pneumonococcus (25-60%)
- haemophilus influenzae (5-15%)
What is the difference in presentation of atypical pneumonia?
- there is minimal sputum and a chronic onset
What 4 bacteria can atypical pneumonia be caused by?
- M. pneumoniae
- Chlamydiophila psittaci
- Coxiella burnetti
- Legionella pneumophila
What is the clinical presentation of bacterial pneumonia?
- chest pain, pain on inhalation sometimes
- a cough which may produce sputum
- shortness of breath (daysnoea)
- abnormal cracking sounds called rales
- evidence of consolidation on an x- ray
What typically provides the diagnosis for pneumonia?
- sputum is the specimen of choice, usually the sample is taken the morning before breakfast
- gram stain (gram positive diplococci should be seen)
- serology
Is there anyway to prevent pneumonia?
Yes- there is a pneumonococcus capsular vaccine for adults
- 7 valent vaccine for infants
What are different viruses that are known to cause pneumonia?
- influenza A or B
- parainfluenza virus
- measles
- RSV
- adenovirus
- CMV
- varicella-zoster virus
Where does viral pneumonia typically invade?
- typically invades through the RT or the blood
What are the 3 different kinds of influenza viruses? Describe them
Influenza A: cause epidemic and pandemics, can be found in animal reservoirs (birds)
Influenza B: causes epidemics only and do not involve animal hosts
Influenza C: cause no epidemics, with only mild respiratory illness
What is the basic structure of the influenza virus?
H and N antigens
- characterizes different strains
- has a single stranded RNA genome
What is antigenic drift
small mutations occurring to the H and N antigens constantly
- when changes in these antigens allow the virus to multiply significantly in individuals with immunity to preceding strains - the new subtype can infect the community
- seen in all types of influenza
What is antigenic shift
- less common and only seen in influenza A
- sudden major change in the shift of a lot of antigens at the same time
- this is based on the recombination between different virus strains when they infect the same cell
Describe the mixing vessel hypothesis
- hypothesized that new strains of influenza emerge because influenza virus type A infects pigs, horses and other mammals
The transmission and outbreak of influenza is _____
seasonal
How is the avian flu transferred?
- through the movement of poultry and products
How does the influenza virus enter into the body?
- enters in droplets that attach to the silica acid receptor on epithelial cell surface via H spikes
- cytokines cause fever and chills, muscle aches, runny nose and a cough
In 7-10 days, the influenza virus may lead to _____ or interstitial _____
- bronchitis
- pneumonia
- secondary bacterial infection
Who is at a higher risk of influenza?
- over 60 years old or in pregnancy
How is a vaccine typically formulated for influenza?
- egg grown virus which is purifies -> formalin inactivated and then extracted by ether
- purified H and N antigens are then used to split the vaccine
- extract virus strains and reviewed annually
- offers 70% protection
What are some of the most common neuramidase inhibitors that act as antivirals?
- zanamivir and oseltamivir
The SARS-CoV virus is ____ RNS virus
single stranded
What are the main signs and symptoms associated with a SARS-CoV infection?
- fever above 38 degrees, cough, shortness of breath/difficulty breathing, chest X-ray- looks similar to those using pneumonia
- 10% fatality associated
What has lead to the increase in SARS cases in recent years?
- changes in viral reservoir and human eating habits
- consumption of exotic animals (bats, civet cats, etc)
- SARS-CoV like virus was detected in Himalayan palm civet cats, Chinese ferret badgers and horseshoe bats
The evolution of the SARS virus has lead to what?
- improved animal to human and human to human transmission
- the virus is also so transmissible because it is table at room temperature for 2 days on surfaces and 4 days on feces
What bacteria is tuberculosis found in?
- mycobacterium tuberculosis
- oldest documented communicable disease
Tuberculosis is an ____, disinfectant resistant infection
acid-fast
The primary infection of tuberculosis is in the ____ (asymptomatic here). From here there is a hypersensitivity reaction to mycobacterium Ag , leading to granuloma and a dissemination through the bloodstream
lung
What is the gold standard for diagnosing a tuberculosis infection?
- tuberculin test as well as signs and symptoms of tuberculosis
- can also do a culture
Why is a culture generally not used to test for tuberculosis?
- cultures can take a long time to develop, up to 6 weeks
What is the process of doing a tuberculin skin test?
- standardized amount of purified protein derivative is injected intradermally and then read 48 hours later
- in immunocompetent individuals- the induration should be around 10 mm -> leads to a positive test
- in immunosuppressed individuals- the induration should be over 5 mm and that should lead to a positive test
What is often used as drugs to treat tuberculosis?
- 3 drug combination therapy of isoniazid, rifampin and ethambutol- these prevent the development of resistance
- long term treatment of these drugs is required- around 6-9 months of treatment
What is considered multi drug resistant TB?
- resistant to at least INH and rifampin
What is considered to be XDR-TB?
MDR TB and fluroquinolone, and at least one of the three injectable second line drugs (capreomycin, kanamycin and amikacin)
What is cystic fibrosis?
- an inherited disease of the secretary glands
- caused by the inheritance of the cystic fibrosis transmembrane conductance regulator gene (CFTR)
- 1/2500 people
- singled by pancreatic insufficiency, abnormal sweat electrolyte concentrations and production of very viscid bronchial secretions
The lung being colonized by what three pathogens signals the occurrence of cystic fibrosis?
- P. aeruginosa (almost all patients 15-20 years old)
- S. aureus
- B. cepacia
Almost all cystic fibrosis patients aged 15-20 years old have lungs that are colonized by ______
P. aeruginosa
