Respiratory tract infections Flashcards
What kind of infection are most
RTI’s?
- Viral
What is the main problem with RTI’s?
- Secondary infections
In what ways is the nasopharynx very adapted to help prevent infection?
- Saliva - designed to try and absorb viral particles and various bacteria
- Have lymph nodes - they help to recruit B and T cells
What are the 3 most common infections in the upper respiratory tract?
- Sinusitis
- Tonsilitis
- Pharyngitis
What does Streptococcus pyogenes cause?
- Causes 10%-20% of cases of acute pharyngitis
- Sudden onset, mostly in 5-10yo children
- Often mild but toxic illness c an be severe
What percentage of tonsillitis/pharyngitis is caused by viruses?
about 70%
What viruses can cause the common cold? (4 points)
- Rhinovirus, Adenovirus, Parainfluenza virus, and others
What are examples of 3 viruses that can cause upper RTI’s?
- Rhinovirus = mild symptoms in the common cold
- Influenza virus = Pharyngitis and lower RTI’s
- Herpes simplex virus type 1&2 = May be severe, with palatal vesicles or ulcers
What virus causes glandular fever?
- Epstein Barr virus
What % of sore throats are caused by S. pyogenes (group A)?
About 25%
What % of children are asymptomatic carriers of Sterptococcal sore throats?
15-20%
Does group C&G streptococci ever cause strep sore throats?
- Occasionally
What are examples of Strep virulence factors? (4 points)
- Pyrogenic exotoxins
- Streptolysins
- Hyaluronidase
- M protein
What is hyaluronidase?
A family of enzymes that catalyse the degradation of hyaluronic acid
What is M protein?
- A capsule
- Usually used to surround the organism and prevent desiccation
- Looks kind of like self protein
- Attacks cardiac tissue - rheumatic fever
What is rheumatic fever?
A possible complication of strep throat infection or scarlet fever that can cause a wide range of secondary symptoms from joint inflammation to heart valve damage
What are possible complications of Strep sore throat? (6 points)
- Peri-tonsillar abscess
- Otitis media or sinusitis
- Scarlet fever (immune response to the organism)
- Rheumatic fever
- Rheumatic heart disease
- Acute glomerulonephritis
What is bronchitis?
- Inflammation of the tracheobronchial tree
When does acute bronchitis usually occur?
- During the winter months
What is the common cause of acute bronchitis?
- Most often viral
What makes bronchitis chronic?
- Productive cough on most days during at least 3 months in each of 2 successive years
What % of the population does chronic bronchitis affect?
10-25%
What are predisposing factors of chronic bronchitis? (4 points)
- Smoking
- Infection
- Air pollution
- Allergies
What is the common cause of chronic bronchitis?
- Viral & bacterial agents
What is Whooping cough?
- Cough so much till you are sick and cannot stop coughing
- Takes a lot of energy out of you
- Produces an exotoxin which stimulates the upper bronchi
What is the organism that causes whooping cough?
- Bordatella pertusis
What can be given to a patient with a RTI? (3 points)
- Decongestants
- NSAID’s
- Antibiotics
- (where appropriate)
Bacteria causes 10% of RTI’s. What are 4 examples of these?
- Bordatella pertussis
- Mycoplasma pneumoniae
- Chlamydia pneumoniae
- Haemophilus influenzae
How often are people infected with Myobacterium tuberculosis?
- New infection every second
How much of the entire global population is infected by myobacterium tuberculosis?
- 1/3 of the entire global population
- 1% of the population infected every year
How many deaths per year are due to myocardium TB?
- 3 million (this is increasing)
What % of deaths of myocardium TB are preventable?
25%
What is the treatment of TB?
- Triple therapy - streptomycin, para-aminosalicylic acid & isoniazid
- Long term - take antibiotic for about 6 months
- DOTS - Directly Observed Treatment Short course
What is the % cue rate for TB?
- 95%
- Prevents transmission
What are some examples of high risk factors of TB?
- HIV infection
- Injection drug abuse
- Alcoholism
What are some symptoms of TB?
- Malaise
- Productive cough for more than 3 weeks
- Headache, fever
- Weight loss
- Night sweats
- Blood in sputum
What is pneumonia?
- An inflammatory condition of the lung - especially affecting the microscopic air sacs (alveoli)
What is pneumonia typically caused by?
- Infections, but multi-factorial
- Bacteria, viruses, fungi and parasites
What are the clinical features of pneumonia? (5 points)
- Sudden or insidious onset
- Fever, rigors, malaise
- Shortness of breath, rapid shallow breathing, cyanosis
- Cough producing purulent sputum
- Consolidation of lungs, on clinical and radiographic examination
What are 4 examples of pathogens that cause community-acquired pneumonia?
- Streptococcus pneumoniae
- Mycoplasma pneumoniae
- Haemophilus influenzae
- Legionella pneumophila
What are 4 examples of pathogens that cause hospital acquired pneumonias?
- Staphylococcus aureus
- Gram-negative bacilli
- Klebsiella pneumoniae
- Escherichia coli
What is the main causative agent in bacterial pneumonia?
- Streptococcus pneumonia
Who does streptococcus pneumonia usually affect? (3 points)
- young, elderly and immuno-compromised
How many cases of adult pneumococcal pneumonia occur per year?
50,000
How many fatalities per year are caused by Streptococcus pneumonia?
- 9000 fatalities
How many under 5’s in the UK are admitted to hospital with pneumococcal pneumonia?
1 in 200
What kind of infection is pneumonia?
- Encapsulated bacterial infection
- Very good at avoiding the immune system
- Has a capsule surrounding things
- Organisms of inflammatory nature = gram positive
What does the capsule of the infective agent of pneumonia do? (4 points)
- Covers antibody or C3b bound to bacterial surface
- Prevents contact between phagocyte receptor and opsonin
- Binds protein H (targets C3b) for degradation
- Lessens amount of C3b reaching bacterial surface, opsonising capsule
What is the clinical management of pneumonia?
- Antibiotics (plus hospitalisation)
- Vaccination (23 different serotypes)
Why are vaccinations becoming a more common way of treating pneumonia?
- Antibiotic therapy is increasingly ineffective due to increasing resistance of isolates
- Vaccination strategy based on 23 different stereotypes
- Polysaccharide antigens ineffective at promoting memory - T-cell independent
- Conjugate vaccines of polysaccharides and proteins appear efficaceous, with proper clinical intervention
How is Legionnaire’s disease transmitted? (2 points)
- Inhalation of aerosols from contaminated water
- Aspiration of oropharyngeal colonised bacteria
What are the symptoms of Legionnaire’s disease? (4 points)
Initially influenza-like which progress to a severe pneumonia
- Other features include mental confusion, renal failure and GI symptoms
What is the drug of choice to treat Legionnaire’s disease?
Erythromycin
- It is unresponsive to penicillin
What can prevent hospital-borne pneumonia?
- Toothbrushing
What are the 3 types of influenza
Type A, B and C
What is the size of the influenza virus?
- 80-120nm
What 3 types of particles are present in the influenza virus?
- Pleomorphic, spherical and filamentous particles
Does the influenza virus contain RNA or DNA?
- Single-stranded RNA
The influenza virus has a segmented genome. How many segments are in type A and B?
- 8 segments
What 2 things are on the surface of the virion of influenza?
- Hemagglutinin
- Neuraminidase
How is the influenza virus classified?
- On the basis of hemagglutinin and neuraminidase
How many subtypes of HA and NA are known to exist in the animal strain of influenza?
- 15 of HA
- 9 of NA
How many subtypes of HA and NA are known to exist in the human strain of influenza?
- 3 of HA
- 2 of NA
Which animal strains of influenza can affect humans?
- HA 5, 7 and 9
- Na 7
What is the method of infection and replication of an influenza virus? (6 points) (long answer)
- Virus absorbs to a respiratory epithelial cell by HA spikes and fuses with the membrane
- The virus is endocytosed into a vacuole and uncoated to release its 8 nucleocapsid segments into the cytoplasm
- The nucleocapsids are transported into the nucleus. There the (-) sense RNA strand is transcribed into a (+) sense strand that will be translated into viral proteins that make up the caspid and spikes
- (+) sense RNA is used to synthesize glycoprotein spikes inserted into the host membrane
- The (+) sense RNA strands are used to synthesise new (-) sense RNA strands. These are assembled into nucleocapsids and transported out of the nucleus to the cell membrane
- Release of mature virus occurs when viral parts gather at the cell membrane and are budded off with an envelope containing spikes
Influenza virus can be transmitted through aerosols. How many virions are present per droplet?
- 100,000 to 1,000,000 virions per droplet
Large droplets containing influenza virus are common. What are examples of these? (3 points)
- Sneezing
- Coughing
- Contact with Saliva
What is a rare form of transmission of the influenza virus?
- Airborne over a long distance
What is the incubation period for the influenza virus?
- 18-72 hours
What are examples of symptoms of the influenza virus? (9 points)
- Headache
- Fever
- (extreme) tiredness
- Aches (joint)
- Runny nose
- Sore throat
- Aches
- Coughing
- Vomiting
What is meant by the term ‘prophylaxis’?
- Treatment given or action taken to prevent disease
What are 2 examples of prophylaxis that can be used for influenza?
- Hand washing
- Use of masks
What are the 3 types of inactivated influenza virus that can be included in a vaccine?
- Whole virus
- Subvirion
- Purified surface antigen
- (only subvirion or purified antigen should be used in children. Any of the 3 can be used in adults)
What are 3 examples of categories of people who should receive the influenza virus?
- Women in 2nd or 3rd trimester of pregnancy during flu season
- Household members of persons in high-risk groups
- Health care workers and others providing essential community services
What are 2 examples of antivirals for influenza?
- Adamantanes and Neuraminidase inhibitors
What is an epidemic?
- The occurrence of more cases of a disease than expected in a given area or among a specific group of people over a particular period of time
What is a pandemic?
- An epidemic occurring over a very wide area (several countries or continents) and usually affecting a large proportion of the population
What are 3 examples of pandemic diseases?
- Cholera
- AIDS
- P a ndemic Influenza
The influenza virus tends to undergo changes from time to time. What is the name for this?
- Antigenic variation
There are 2 types of antigenic variation. What are these?
- Antigenic shift
- Antigenic drift
Changes in the antigenic characteristics of influenza viruses determine the extent and severity of influenza epidemics
What is antigenic drift in relation to the influenza virus?
- This term denotes MINOR changes in hemagglutinin and neuraminidase of influenza virus
- This results from mutation in the RNA segments coding for either the HA or NA
- This involves no change in serotype; there is merely an alteration in AA sequence of HA or NA leading to change in antigenicity
What is antigenic shift in relation to the influenza virus?
- This term denotes MAJOR changes in hemagglutinin and neuraminidase resulting from reassortment of gene segments involving two different influenza viruses
- When this occurs, worldwide epidemics may be the consequence since the entire population is susceptible to the virus
Which type of influenza is the most severe?
- Type A
