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IMED3112 > Resp Microbiology > Flashcards

Resp Microbiology Flashcards

1
Q

What is the structure of a virus? (7)

A
  1. capsid - protein shell
  2. Capsomere - proteins
  3. genome - DNA
  4. viral enzymes
  5. Virion - entire unit
  6. Envelope - some viruses have one made from host cell lipid membrane
  7. Glycoproteins - on envelope surface for virulence and adhesion
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2
Q

What are the three shapes of viruses and give an example?

A
  1. Polyhedral - herpes simplex
  2. Helical - ebola and influenza
  3. Complex - bacteriophage eg pox virus
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3
Q

What is the name of the classification according to genome?

A

Baltimore Classification - by genome, ds DNA, ss DNA, ds RNA, ss RNA, -ss RNS, ss RNA-RT, ds DNA-RT

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4
Q

What are the three basic steps of the life cycle of a virus?

A
  1. Entry
  2. Genome expression and replication
  3. Exit
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5
Q

What is the life cycle of HIV?

A
  1. binding - GP120 binds host CD4 receptors
  2. Fusion - between viral envelope and cell plasma membrane so capsid enters host cell
  3. Reverse transcription - viral enzyme RTase turns viral RNA into ds DNA
  4. Integration - viral DNA enters host nucleus and lymphocytes contain HIV genome and replicate
  5. Viral DNA uses host to produce viral RNA and proteins
  6. Assembly - new viral RNA and proteins. HIV proteases cut into final form of immature virions
  7. Budding - immature virions but through host cell membrane creating more infectious virions
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6
Q

Life cycle of COVID-19?

A
  1. Attachment of surface spike protein to ACE2 receptor
  2. Entry - endocytosis into endosome
  3. Fusion and uncoating - viral envelope fuses with endosome membrane and viral RNA released
  4. Translation of RNA forming Viral Replication and Transcription Complex ( host ribosomes transcribed viral RNA to produce two large polyproteins that connect with host ER) VRTC is a protected environment where virus replicated RNA
  5. travel through host ER to Golgi intermediate compartment
  6. viral proteins and newly produced viral RNA bud into ERGIC and form new virions
  7. exocytosis from host cell membrane
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7
Q

Which viruses cause cancer? (7)

A
  1. Hep B - hepatocellular carcinoma
  2. Hep C - hepatocellular carcinoma
  3. HPV - cervical and oropharyngeal
  4. EBV - nasopharyngeal, burkitts
  5. HHV8 - Kaposis sarcoma
  6. HTLV1- adult T cell lymphoma
  7. Merkel cell polyoma virus - merkel cell carcinoma
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8
Q

Causes of pharyngitis? (3)

A
  1. Bacterial - strep pyogenes, arcanobacterium haemolyticum
  2. viral - rhino, corona, parainfluenza
  3. EBV - glandular fever
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9
Q

What is the commonest throat infection infected with strep. pyogenes?

A

Strep. pharyngitis - group A haemolytic strep with abrupt onset sore throat and fever

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10
Q

Complications and treatment of Strep pharyngitis?

A

Complications
1. Supprative - otis media, sinusitis, meningitis
2. Non-supprative - rheumatic fever, glomerulonephritis
3. Major - carditis, subcutaneous nodules
4. Minor - arthralgia, fever, prolonged PR intervals
Treatment – penicillin but not amoxycillin or ampicillin as they cross react with EBV

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11
Q

Cause, symptoms and treatment of acute epiglottitis?

A

Inflammation of epiglottis from HiB. Children present with common cold for 1-2 days, sudden onset high fever and sore throat. Do not try to visualize larynx as it will inflame. Treat with ceftriaxone or amoxycillin

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12
Q

Cause, symptoms and treatment of diptheria?

A

bacteria adheres to mucosa, releases exotoxin locally which causes cell death, necrosis of tissue and membrane obstruction from dead tissue. Systemically it causes myocardial toxicity and neurotoxicity with fever, pallor, exhaustion. Treat with penicillin, erythromycin

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13
Q

Cause, symptoms and treatment of croup?

A

clinical syndrome caused by many resp pathogens, commonly parainfluenza. Clinical features are fever, hoarsness, barking cough, can me mild or with obstruction and inflammatory onstruction of subglottic area. Manage by maintaining airway, fluid balance and rest and steroids

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14
Q

Cause, symptoms and treatment of sinusitis?

A

Infection of paranasal sinuses from strep. pneumoniae, H. influenzae, moraxella catarrhalis
Symptoms - fever, unilateral face swelling, pain, headache, blocked nose, nasal drip/discharge
Treatment - amoxycillin
Complications - mastoiditis, meningitis, brain abscess

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15
Q

Cause, symptoms and treatment of Otitis media?

A

Peak age - 6-18 months with allergic conditions predisposing for infection
Cause - usually strep pneumoniae or HiB causing congestion of mucosa obstructing Eustachian tube, trapping fluid causing bacterial overgrowth
Symptoms - ear pain, fever, hearing impairment, discharge
Treatment - amoxycillin
Complications - mastoiditis, meningitis, brain abscess

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16
Q

Cause, symptoms and treatment of Otitis externa?

A

infection of external ear canal, exacerbated by moisture (swimmers ear) from S. aureus, strep pyogenes, candida albicans, pseudomonas aeruginosa

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17
Q

Cause, symptoms and treatment of pertussis? What are the three phases?

A

Cause - bordetella pertussis
Symptoms - violent cough, primarily school children. Droplet spread attaches to nasopharynx, produces toxins and damage to trachea and bronchi
Phases
1. Catarrhal - fever, mild cough
2. Paroxymal - after 1-2 weeks, coughing followed by single whoop
3. convalescent - after 2-4 weeks asting months with diminishing cough
Complications - subconjunctival haemorrhage, pneumothorax, rib fracture, hernia
Treatment - clarithromycin

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18
Q

What is bronchopneumonia and what are the 4 phases?

A

Infection of lung parenchyma which proliferate within alveoli
Phases
1. oedema - fluid leak from bv to tissue
2. Red hepatization - red liver
3. Grey hepatization - dying tissue
4. Resolution

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19
Q

Most common causes of community acquired pneumonia?

A

Bacterial - strep pneumonia, HiB, S. aureus, klebsiella, legionella
Viral - influenza, parainfluenza
Fungal - cryptococcus neoformans, aspergillus, pnemocystis jirovecii

20
Q

Three main cases of atypical pneumonia?

A
  1. Legionella pneumophila/longbeachea - waterborne amoeba or potting mix
  2. Chlamydophila psittaci - birds, poultry, cattle, pigs, sheep
  3. Coxiella burneti - australian disease outbreak from cattle, farms, milk, meat
21
Q

Treatment of mild, moderate and severe pneumonia?

A

Mild - amoxycillin or clarithromycin
Moderate - penicillin or clarithromycin
Severe - ceftriaxone or penicillin plus azithromycin

22
Q

What does aspiration pneumonia treatment need to include

A

Additional anaerobe cover - tazocin, metronidazole

23
Q

What are the three main factors influencing ventilator acquired pneumonia?

A
  1. oropharyngeal colonisation replaced by pathogens
  2. aspiration - endotracheal tube bypasses, keeps out but traps bacteria in
  3. compromised defenses - trauma leading to immunoparalysis
24
Q

Causes of mycobacterium pneumonia and clinical implications?

A

M. avium and M. intracellular complex from soil, enviroment causing chronic pneumonia in pre-existing lung disease. right middle lobe, left lingula which isnt cleared by vigorous cough (Lady Windemere syndrome) treated by clarithromycin

25
Q

What is empyema?

A

frank pus in pleural space from pre-existing pleural fluid which bacteria invades causing thick, viscous and opaque pus needing to be drained

26
Q

What is pleural effusion and what are the two types of presentations?

A

Abnormal collection of fluid in pleural space due to excess fluid or decreased drainage and is common manifestation of pleural disease, cardiopulmonary, oncotic or hydrostatic
1. Transudates (low in protein) results from imbalance of oncotic and hydrostatic pressure eg, cardiac failure, cirrhosis, hypoalbuminaemia
2. Exudates (high in protein) results from inflammation of pleura or decreased lymphatic drainage eg, infection, cancer, PE

27
Q

What are the parapneumonic pleural effusion types?

A
  1. Uncomplicated - exudative, neutrophilic effusions with increasing passage of interstitial fluid as result of inflammation associated with pneumonia.
  2. Complicated - bacterial invasion with increased neutrophils, decreased glucose. Bacteria seen and cultured
28
Q

What is bronchiectasis, causes and clinical implications?

A

Abnormal and permanently dilated bronchi due to inflammation and destruction of bronchial architecture with inability to clear secretions
Causes - infection (pneumonia, TB, MAC, pertussis), autoimmune, CF
Leads to further infection with pseudomonas and HiB, release of toxins with host immune system response triggering further damage, mucus plugging and colonization. Chronic cough, haemoptysis, SOB

29
Q

What causes tropical pneumonia?

A

Burkholderia pseudomallei

30
Q

What is melioidosis and why is it important?

A

Infection from soil/water presenting as septic illness or chronic infection mimicking TB or cancer. Treat with meropenem

31
Q

Most common cause of HIV and what level of CD is classified as low?

A

Pneumocystis pneumonia most common cause of infection when immue fails. Normal levels 500-1500 but opportunistic infection when CD4 less than 200

32
Q

3 complications of aspergillus infection and on what population?

A

Cancer and transplant patients with suppressed immune. Main pathogen in A. fumigatus
1. Allergic bronchopulmonary aspergillous
2. Aspergilloma
3. Invasive aspergillosis

33
Q

What is CF and what are the implications of infection?

A

Abnormal transport of Cl and Na across epithelium causing thick viscous secretions.
Inflammation and bacterial infections destroy lung causing bronchiectasis mainly caused by s. aureus, HiB, pseudomonas aeruginosa

34
Q

What is tuberculosis?

A

Chronic granulomatous disease caused by mycobacterium tubetculosis. It is phagocytosed by macrophages, survives and grown. Infected phagosomes fuses with lysosomes and a granuloma walls of infection from rest of body beofre spreading. 1/3 world infected

35
Q

Outline TB progression?

A

Environmental expsoure leads to 70% uninfected, 30% infected.
Infected shows memory immune response with 5-10% primary TB (localized cessation in lymph node which can be healed or latent)
Infected goes 90% to containment and persistence with latent TB or Reactivation (secondary TB with haematogenous dissemination causing miliary TB or localized caseating destructing lesions)

36
Q

What is the connection between TB and HIV?

A

HIV promotes pregression to active TB disease. HIV negative have 10% lifetime risk of TB while HIV positive have 10% annual risk. TB leading cause of death in those infected with HIV but can be prevented through isoniazide

37
Q

What is the connection with TB and poverty?

A

large association due to
1. increased exposure due to overcrowding
2. Incresed risk of disease after infection
3. less likely diagnosis and proper treatment
4. latent is more likely to reactivate due to nutritional and vit D deficiency and increased stress

38
Q

Clinical manifestation of pulmonary TB? (4)

A
  1. productive prolonged cough
  2. chest pain
  3. haemoptysis
  4. systemic symptoms of fever, chills, night sweats, loss of appetite and weight
39
Q

7 was to diagnose TB?

A
  1. chest x-ray - usually upper lobe
  2. Tuberculin skin test - measure of infection not disease looking at inflammation response
  3. IGRA - interferon gamma release assay
  4. Sputum
  5. Culture - most sensitive
  6. Molecular - presence fo Tb and what it resistant to
  7. Urine LAM
40
Q

Treatment of TB?

A

MDR - aminoglycosides
XDR - fluoroquinolones

41
Q

Difference between influenza B and C?

A

B has less capacity to invade populations immune system and C only causes mild infection mainly in children

42
Q

What are the two surface proteins of Influenza A?

A
  1. Haemagglutin - HA mediated binding and entry into host
    2, Neuraminidase - NA mediated release of daughter virus from infected cells
43
Q

Outline antigenic drift vs shift?

A

Drift - mutations in coding gene (more likely NA) causing yearly outbreaks but viral subtype remains the same eg H3N2 stays H3N2 but population has less immunity.
Shift - major antigenic changes resulting from genetic reassortment and exchanging of materials between animals and humans. H2N2 to H3N2 causing major epidemics/pandemics

44
Q

What is RSV and what is it most likely to cause?

A

Produce bronchiolitis in infants. Mucosal inflammation resulting in blockage by inflammatory exudate or odeema fluid. Lungs become hyper inflated because during inspiration, negative pressure opens alveoli but expiration collapses the bronchioles and traps distal air. Causes fever, tachycardia, wheeze, hyper inflated chest, apnoea

45
Q

What do parainfluenza and croup most likely cause?

A

Acute laryngotrachealis resulting from inflammation and oedema of subglottic larynx and trachea with swelling producing hoarsness, barking cough, and stridors

46
Q

What do you use the Ziehl-Neelsen stain for?

A

Mycobacterium as they cannot take up crystal violet due to waxy hydrophobic cell wall. Peptidoglycan in call wall joined to mycolic acid which is resistant to decolorization so methylene blue is added to stain

IMED3112 (17 decks)

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