WK 9- Respiratory Tract Infections Flashcards
What are the 6 basic diseases of the respiratory tract
Rhinitis Pharyngitis Croup Bronchitis Bronchiolitis Pneumonia
What are the symptoms of rhinits
copious watery nasal discharge & obstruction, sneezing, +/- mild sore throat, +/- cough, little or no fever
What are the main pathogens that cause rhinitis
50% rhinovirus, 15% coronaviruses and then remaining are caused by enteroviruses (coxsackie), RSV, parainfluenza virus, adenovirus
What are the pathogens that cause pharyngitis
most are viral- influenza, adenovirus, RSV, parainfluenza, rhinovirus→ most have a viral cause
What are the symptoms of laryngotracheobronchitis (croup)
Barking cough (young children), hoarsness (older children), inspiratory stridor and respiratory distress
What are the complications of croup
usually mild and self limited but can progress to significant laryngeal obstruction and cyanosis
What are the pathogens that cause croup
Most common parainfluenza cause, then RSV and influenza
What is the main cause of acute bronchitis
Influenza, Parainfluenza, RSV
What are the pathogens that cause bronchiolitis
is RSV, then hMPV, parainfluenza and influenza
What are the symptoms of bronchiolitis
Inflammation of the bronchioles
- Rapid & laboured breathing, cough, expiratory wheezing, cyanosis, atelectasis, marked emphysema
- potentially fatal in newborns and thought to be a cause of SIDS
What pathogens cause pneumonia
Viruses are the main cause of pneumonia in children
- Most common= RSV, hMPV, Parainfluenaza, influenza, adenovirus
- Less common= measles, varicella, CMV
Describe the genome of the influenza virus
-ve sense RNA genome that is in 8 different segments
What are the glycoproteins present on the viral envelope of influenza
haemaglutinin (HA) allows attachment and entry into cell and neuramindase (NA) is important in viral release from the host cell (allows it to infect other cells)
What are the 3 types of infleunza and which is most prevalent in humans
Influenza A: affects animals and bird species and a major cause of epidemics and pandemics
Influenza B: human pathogen only that causes localised outbreaks
influenza C: not generally considered a human pathogen
How is influenza subtyped
-Subtyping is based on NA and HA subtypes–> There are 18 known subtypes of HA and 11 of NA in animals and man
What subtypes of NA and HA are found in humans
only H1-3 and N1&2 are commonly found in humans
What is antigenic drift
- Occurs in both influenza A and B
- Occurs when there are small repeated point mutations when coding for HA and NA–> this causes the strain to be slightly mutated, meaning that the body has no immune defence against it (no antibodies present as it is technically a new strain) -> allows for reinfection
- this is the reason for an updated flu vaccine to be available every year
What is antigenic shift
-what strains does it affect
- Influenza A only
- More extensive and sudden alteration in viral antigens, occurs occasionally & unpredictably
- Is due to the exchange of genetic material between 2 different strains of Influenza A E.g. 2 influenza strains (1 human, 1 avian) co-infecting a single pig cell
- New strains are anitgenically different= able to cause pandemics
How is influenza transmitted (2 ways)
Respiratory droplet= released from infected person and can land on mucous membrane of another person
Contact spread= When infected respiratory secretions come into contact with a person’s hand and is then transferred to their mouth, nose or eyes
What is the process of influenza replication
- Virus binds to host cell sialic acid receptor via HA & enters via receptor-mediated endocytosis→ 2. Fusion, uncoating of virus → 3. transport into nucleus
- Genome replication via viral RNA-dependent RNA polymerase (turns RNA into mRNA so can eventually be turned into a protein) –> 5. Translated into the cytoplasm–> Assembled at surface of host cell membrane and newly formed virus buds out with HA & NA on viral envelope
What is the pathogenesis of influenza
Infection localised to the RT however initiates a cascade of immune reactions
→Cytokine release, immune cell activation causes systemic symptoms e.g. fever
-Flu NS1 enables the virus to evade & antagonise the IFN response
-Influenza also causes tissue damage
What is the presentation of influenza
-IP and symptoms
- Short incubation period: 18 - 72hrs
- Sudden onset of fever & resp Sx such as cough, sore throat, runny/stuffy nose plus headaches, myalgia & often extreme fatigue
What complications can arise from influenza
pneumonia→ Flu-related complications can occur at any age, however most likely in elderly & those with chronic underlying diseases (initial damage to the URTI allows for secondary infection leading to pneumonia→ commonly by staph aureus)
What complications arise from severe influenza
viral pneumonitis, bacterial pneumonia, encephalitis, myositis, carditis
Who are most likely to be affected by complications of influenza
-Most severe in:
→ Children: may not have any protective Ab, small diameter of respi tract is also an important factor
→ Elderly: waning immune system, COPD, chronic disease
How is influenza managed
-Symptomatic→ Fluids, antipyretics, rest
-Neuraminidase inhibitors
→ E.g. Oseltamivir (Tamiflu), Zanamavir (Relenza)
How does a neuraminidase inhibitor work
Act as competitive inhibitors of the NA enzyme active site (NA assists release of viral from cell→ preventing NA stops virus being released from host cell and decreases escalation of infection)
-If given early may ↓ viral shedding, disease severity, duration & symptoms
What does each strain cause; H1N1 H7N7 H9N2 H7N9
H1N1= swine flu
H5N1 (“Bird flu”, HPAI- highly pathogenic avian influenza): Endemic in many bird populations, esp. SE Asia→ Human to human transmission not efficient
H7N7: numerous outbreaks in Europe with some human to human transmission
H9N2: some cases in young children in Hong Kong in recent years
H7N9: Outbreak began in China March 2013→High mortality rate
What does RSV mean
- what family does RSV belong to
- What proteins are found on the viral envelope
- Respiratory syncytial virus
- Paramyxoviridae
- Surface spikes->G protein (attachment) and F protein (fusion)–> fusion allows for the viral envelope to fuse with the host cell and inject viral genome
What diseases do RSV cause
Primary cause of bronchiolitis and pneumonia in infants→ highly contagious
-carries a significant risk of death in those who are immunocompromised
What symptoms are caused by RSV
-Illness begins like a common cold, however, within 24 hours the baby may be severely ill with cyanosis and distress
What does hMPV stand for
Human metapneumovirus (hMPV)
What family does hMPV belong to
Paramyxoviridae
What type of genome does hmPV have
ssRNA virus
What symptoms does hMPV cause
-is this the same as RSV
same as RSV
Fever.
Severe cough.
Wheezing — a high-pitched noise that’s usually heard on breathing out (exhaling)
Rapid breathing or difficulty breathing — the child may prefer to sit up rather than lie down.
Bluish color of the skin due to lack of oxygen (cyanosis)
What family does parainfluenza virus
paramyxoviridae family
What symptoms does parainfluenza cause
- Important respiratory pathogens in children & adults
- Causes LRTIs mostly e.g. croup, pneumonia
- Epidemiology & pathogenesis similar to RSV infection
How is adenovirus different to other respiratory viruses
has a double stranded DNA genome
What symptoms does adenovirus cause
nasal congestion, cough, pharyngitis in older children, pneumonitis may be seen in young adults
What kind of genome does rhinovirus have
- what family do they belong to
- what are the symptoms
-RNA genome
-Picornaviridae family
–> causes the common cold
-Nasal dryness or irritation - May be first symptom.
Sore throat or throat irritation – Common and bothersome initial symptom.
Nasal discharge, nasal congestion, and sneezing – Intensify over 2-3 days.
Headache.
Facial and ear pressure.
How can people be reinfected with rhinovirus
- Has multiple serotypes–> no cross protection between serotypes
- have antigenic drift
What is the serious type of coronavirus
Mers-CoV: Middle East Respiratory Syndrome Coronavirus
→ most commonly related to cornovirus in bats→ Genetically distinct from SARS CoV & different epidemiology
What are the IP and symptoms of coronavirus
- IP= 2 wks
- Causes acute, severe respiratory illness, Fever, cough, SOB, breathing difficulties
- Severe cases mainly in older males with underlying conditions (co-morbidities)→ Mild & asymptomatic cases in all ages, including children, and without underlying conditions
What lab dx are used to diagnose respiratory infections
- NPA (nasopharyngeal aspirate), NP swab–> collect cells for PCR–> need to collect cells during the viral shedding phase
- Rapid antigen detection test but only RSV and influenza
- Serology= mainly only for influenza (looks at tire)
Why is it important to diagnose viral resp infection
- viral resp tract infection can cause serious illness
- antiviral tx exists for some infections (ie. tamiflu)
- diagnosis can assist with infection control and reduce the use of antibiotics
- epidemiology provides the basis for immunisation programs
- influenza virus used for vaccine
What are the main causes of bacterial resp infection
Staph aureus, H.influenzae, M.catarrhalis
What bacteria cause nosocomial pneunomias/pneumonia in immunosuppressed
Klebsiella, Pseudomonas, Staph
What bacteria cause atypical pneumonia
Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella sp, Pneumocystis, etc
How does meliodosis cause pneumonia
lives in soil, tracts to lungs once person is infected, will drag staph into the lungs and cause pneumonia→ requires different and more prolonged therapy and can kill (prevalent in wet season)
What is the pathogenesis of bacterial resp infections
- enter via inhalation, aspiration of haematogenous spread
- replicate in/on resp epithelium and cause inflammation, increased mucous and impaired mucocilliary function (preventing their removal)
What symptoms are associated with bacterial pneumonia
-Respiratory symptoms:
→ cough with sputum (collect sputum for investigation), fever, pleuritic chest pain, tachypnoea
Non-respiratory symptoms: headache, diarrhea, nausea, myalgia, confusion, abdopain, vomiting
What diagnostic samples are needed for microbial diagnosis of bacterial resp infections
- Sputum MC&S→ gram stain and test for antibiotic resistance
- Throat swabs – pharyngitis, epiglottitis→need a gel swab to culture the bacteria
- Blood cultures→
- s.pneumonia is alpha haemolytic
- h. influenza= cocci bacill gram neg
What bacteria causes pertussis
bordetella pertussis
What is the pathogenesis of pertussis
Attachment (HA, fimbriae)
–>releases numerous toxins (affect inflammatory response or damage respiratory epithelium)
What are the symptoms of pertussis
-Characteristic paroxysmal cough with inspiratory whoop→ can cause significant morbidity in adults, but can be fatal in young infants
What diagnostic tools are available for pertussis
NPA or NP swab for PCR and blood for serology
What bacteria causes TB
Mycobacterium tuberculosis (Mtb)
What is the pathogenesis for TB and what symptoms does it cause
Mtb can survive and multiply within alveolar macrophages due to thick cell wall (resists macrophage destruction and will instead hide and replicate within the macrophage→ causes a granuloma)→ Reactivation of dormant Mtb may occur if immune system decreases
-Symptoms of infection mostly due to host immune response (CMI)→ fever, cough, haemoptysis, sweats, weight loss→ may even be asymptomatic
What lab dx are used for TB
sputum for MC&S→ stain weakly with a gram, so need to use a Ziehl-Neelsen stain for “acid-fast bacilli” with specialized media (for prolonged culture)
What are the 3 common bacterial pathogens causing otitis media?
streptococcus pneumonia (35%), non-typable strains of haemophilus influenza (25%), Moraxella catarrhalis (15%)
What is the gram stain for strep pneumo
Gram positive
What is the gram stain for m.cattarhalis
Gran negative
What is the gram stain for non-typable haemophilus influenzae
Gram negative
How can haemophilus influenza infection of the epiglottis be prevented
Hib Vaccine
