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ID > WK 9- Respiratory Tract Infections > Flashcards

WK 9- Respiratory Tract Infections Flashcards

1
Q

What are the 6 basic diseases of the respiratory tract

A 
Rhinitis
Pharyngitis
Croup
Bronchitis
Bronchiolitis
Pneumonia
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2
Q

What are the symptoms of rhinits

A

copious watery nasal discharge & obstruction, sneezing, +/- mild sore throat, +/- cough, little or no fever

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3
Q

What are the main pathogens that cause rhinitis

A

50% rhinovirus, 15% coronaviruses and then remaining are caused by enteroviruses (coxsackie), RSV, parainfluenza virus, adenovirus

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4
Q

What are the pathogens that cause pharyngitis

A

most are viral- influenza, adenovirus, RSV, parainfluenza, rhinovirus→ most have a viral cause

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5
Q

What are the symptoms of laryngotracheobronchitis (croup)

A

Barking cough (young children), hoarsness (older children), inspiratory stridor and respiratory distress

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6
Q

What are the complications of croup

A

usually mild and self limited but can progress to significant laryngeal obstruction and cyanosis

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7
Q

What are the pathogens that cause croup

A

Most common parainfluenza cause, then RSV and influenza

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8
Q

What is the main cause of acute bronchitis

A

Influenza, Parainfluenza, RSV

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9
Q

What are the pathogens that cause bronchiolitis

A

is RSV, then hMPV, parainfluenza and influenza

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10
Q

What are the symptoms of bronchiolitis

A

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
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11
Q

What pathogens cause pneumonia

A

Viruses are the main cause of pneumonia in children

  • Most common= RSV, hMPV, Parainfluenaza, influenza, adenovirus
  • Less common= measles, varicella, CMV
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12
Q

Describe the genome of the influenza virus

A

-ve sense RNA genome that is in 8 different segments

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13
Q

What are the glycoproteins present on the viral envelope of influenza

A

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)

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14
Q

What are the 3 types of infleunza and which is most prevalent in humans

A

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

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15
Q

How is influenza subtyped

A

-Subtyping is based on NA and HA subtypes–> There are 18 known subtypes of HA and 11 of NA in animals and man

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16
Q

What subtypes of NA and HA are found in humans

A

only H1-3 and N1&2 are commonly found in humans

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17
Q

What is antigenic drift

A
  • 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
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18
Q

What is antigenic shift

-what strains does it affect

A
  • 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
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19
Q

How is influenza transmitted (2 ways)

A

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

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20
Q

What is the process of influenza replication

A
  1. Virus binds to host cell sialic acid receptor via HA & enters via receptor-mediated endocytosis→ 2. Fusion, uncoating of virus → 3. transport into nucleus
  2. 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
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21
Q

What is the pathogenesis of influenza

A

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

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22
Q

What is the presentation of influenza

-IP and symptoms

A
  • 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
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23
Q

What complications can arise from influenza

A

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)

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24
Q

What complications arise from severe influenza

A

viral pneumonitis, bacterial pneumonia, encephalitis, myositis, carditis

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25
Q

Who are most likely to be affected by complications of influenza

A

-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

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26
Q

How is influenza managed

A

-Symptomatic→ Fluids, antipyretics, rest
-Neuraminidase inhibitors
→ E.g. Oseltamivir (Tamiflu), Zanamavir (Relenza)

27
Q

How does a neuraminidase inhibitor work

A

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

28
Q 
What does each strain cause;
H1N1
H7N7
H9N2
H7N9
A

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

29
Q

What does RSV mean

  • what family does RSV belong to
  • What proteins are found on the viral envelope
A
  • 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
30
Q

What diseases do RSV cause

A

Primary cause of bronchiolitis and pneumonia in infants→ highly contagious
-carries a significant risk of death in those who are immunocompromised

31
Q

What symptoms are caused by RSV

A

-Illness begins like a common cold, however, within 24 hours the baby may be severely ill with cyanosis and distress

32
Q

What does hMPV stand for

A

Human metapneumovirus (hMPV)

33
Q

What family does hMPV belong to

A

Paramyxoviridae

34
Q

What type of genome does hmPV have

A

ssRNA virus

35
Q

What symptoms does hMPV cause

-is this the same as RSV

A

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)

36
Q

What family does parainfluenza virus

A

paramyxoviridae family

37
Q

What symptoms does parainfluenza cause

A
  • Important respiratory pathogens in children & adults
  • Causes LRTIs mostly e.g. croup, pneumonia
  • Epidemiology & pathogenesis similar to RSV infection
38
Q

How is adenovirus different to other respiratory viruses

A

has a double stranded DNA genome

39
Q

What symptoms does adenovirus cause

A

nasal congestion, cough, pharyngitis in older children, pneumonitis may be seen in young adults

40
Q

What kind of genome does rhinovirus have

  • what family do they belong to
  • what are the symptoms
A

-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.

41
Q

How can people be reinfected with rhinovirus

A
  • Has multiple serotypes–> no cross protection between serotypes
  • have antigenic drift
42
Q

What is the serious type of coronavirus

A

Mers-CoV: Middle East Respiratory Syndrome Coronavirus

→ most commonly related to cornovirus in bats→ Genetically distinct from SARS CoV & different epidemiology

43
Q

What are the IP and symptoms of coronavirus

A
  • 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
44
Q

What lab dx are used to diagnose respiratory infections

A
  • 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)
45
Q

Why is it important to diagnose viral resp infection

A
  • 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
46
Q

What are the main causes of bacterial resp infection

A

Staph aureus, H.influenzae, M.catarrhalis

47
Q

What bacteria cause nosocomial pneunomias/pneumonia in immunosuppressed

A

Klebsiella, Pseudomonas, Staph

48
Q

What bacteria cause atypical pneumonia

A

Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella sp, Pneumocystis, etc

49
Q

How does meliodosis cause pneumonia

A

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)

50
Q

What is the pathogenesis of bacterial resp infections

A
  • enter via inhalation, aspiration of haematogenous spread
  • replicate in/on resp epithelium and cause inflammation, increased mucous and impaired mucocilliary function (preventing their removal)
51
Q

What symptoms are associated with bacterial pneumonia

A

-Respiratory symptoms:
→ cough with sputum (collect sputum for investigation), fever, pleuritic chest pain, tachypnoea
Non-respiratory symptoms: headache, diarrhea, nausea, myalgia, confusion, abdopain, vomiting

52
Q

What diagnostic samples are needed for microbial diagnosis of bacterial resp infections

A
  • 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
53
Q

What bacteria causes pertussis

A

bordetella pertussis

54
Q

What is the pathogenesis of pertussis

A

Attachment (HA, fimbriae)

–>releases numerous toxins (affect inflammatory response or damage respiratory epithelium)

55
Q

What are the symptoms of pertussis

A

-Characteristic paroxysmal cough with inspiratory whoop→ can cause significant morbidity in adults, but can be fatal in young infants

56
Q

What diagnostic tools are available for pertussis

A

NPA or NP swab for PCR and blood for serology

57
Q

What bacteria causes TB

A

Mycobacterium tuberculosis (Mtb)

58
Q

What is the pathogenesis for TB and what symptoms does it cause

A

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

59
Q

What lab dx are used for TB

A

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)

60
Q

What are the 3 common bacterial pathogens causing otitis media?

A

streptococcus pneumonia (35%), non-typable strains of haemophilus influenza (25%), Moraxella catarrhalis (15%)

61
Q

What is the gram stain for strep pneumo

A

Gram positive

62
Q

What is the gram stain for m.cattarhalis

A

Gran negative

63
Q

What is the gram stain for non-typable haemophilus influenzae

A

Gram negative

64
Q

How can haemophilus influenza infection of the epiglottis be prevented

A

Hib Vaccine

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