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Microbiology > Respiratory Infections > Flashcards

Respiratory Infections Flashcards

1
Q

Dominating bacteria of the respiratory tract.

A

Alpha streptococci

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2
Q

Pharyngitis

A

“Sore throat”

  • Mostly a viral infection > bacterial > Chlamydia/Mycoplasma > Unknown
  • ABs are commonly prescribed, but is infective towards viruses
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3
Q

Common Cold

A
  • Caused by many different viruses
  • No vaccine (b/c it is mild)
  • Rhinovirus (30-50%)
  • Coronavirus (15-20%)
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4
Q

Rhinovirus

A
  • Non-enveloped RNA virus; causative agent for >50% of common colds
  • > 100 serotypes are classified into 3 classes based on the receptor they bind to (90% to ICAM-1)
  • Transmitted mostly by direct contact (sometimes droplets)
  • Optimal growth = 33C / No growth @ 37C
  • Only grows in Upper RT, especially nose area
  • Incubation period = 10-12 hours
  • Self-limiting
  • No vaccines or antivirals; able to take symptomatic medication (antihistamines)
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5
Q

Infectious Mono

A
  • “Kissing disease” due to transmission via saliva
  • Primarily caused by EBV (HHV-4), remains latent
  • Systemic effects on cardio + lymph sys.
  • Very young = mild/sub-clinical infection
  • Older = severe
  • Virus sheds intermittently from salvia through life
  • Heterophile ABs are produced + used for diagnostic lab tests (monospot)
  • Complications: ampicillin rash if infected and given beta-lactam ABs
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6
Q

Burkitt’s Lymphoma

A
  • Associated w/ EBV + malaria endemic areas

- Most common type of childhood cancer in Africa

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7
Q

Streptococcal pharyngitis (Strep Throat)

A
  • Caused only by GAS (streptococcus pyogenes; beta-hemolytic)
  • LAB TESTS ARE NEEDED to differentiate from other types of infection
  • Need to treat all cases of S. pyogenes pharyngitis w/ ABs to prevent sequalae
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8
Q

Scarlet Fever

A

If an individual has Strep Throat with a strain of S. pyogenes that produces erythrogenic toxin

  • Pinkish-red sandpaper-like skin rash
  • High fever
  • Strawberry tongue (painful; loses upper membrane, becomes inflamed)
  • Varies in severity, may progress to Glomerulonephritis or Rheumatic fever
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9
Q

Rheumatic Fever

A

Non-infectious complication of S. pyogenes infection

  • Occurs due to cross-reactivity of bacterial antigens w/ tissue antigens + T-lymphocyte invasion
  • Cause of ~40% of cases w/ rhematic heart disease (often mitral valve damage)
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10
Q

Diphtheria

A
  • Caused by Corynebacterium diptheriae (aerobic Gram + bacillus, non-spore forming)
  • Produces exotoxin that causes death of epithelial cells in the throat (due to inhibition of protein synthesis) AND lysogenized by a bacteriophage
  • Was once the leading cause of mortality in children until vaccination
  • Common in the tropics
  • Symptoms: sore throat, fever, malaise, “bull neck”, thick grey membrane/pseudomembrane (may cause suffocation if it detaches and blocks bronchioles/airways)
  • Treatment: ABs + antitoxins
  • Vaccine: dTap (Tetanus toxoid)
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11
Q

Otitis media

A

Middle ear infections

  • Caused by Moraxella catarrhalis (Gram (-) diplococci)
  • Also caused by S. aureus, “cold viruses”, S. pyogenes
  • Common in children
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12
Q

Corynebacterium diptheriae

A

Aerobic, Gram (+) bacillus, non-spore forming

  • Most are non-pathogenic, unless lysogenized by bacteriophage
  • Causes diphtheria
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13
Q

What are the common causes of bacterial URT infections? Gram morphology.

A
  • Streptococci pneumoniae (Gram (-) diplococci)
  • Haemophillus influenzae (Gram (-) bacillus)
  • Moraxella catarrhalis (Gram (-) diplococci)
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14
Q

Whooping Cough (100 days cough)

A
  • Caused by Bordetella pertussis, which produces many exotoxins + colonizes in ciliated respiratory epithelium
  • Aerobic, gram (-) coccobacillus
  • Transmitted by droplets
  • 3 stages: Catarrhal (cold-like), Paroxysmal (gasping cough), Convalescence (healing)
  • Infants are at higher risk of broken ribs, pertussis pneumonia, oxygen depravation
  • Pathogenicity: FTA filamentous hemagglutinin (adherence), pertussis toxin (diffuses into bloodstream causing systemic effects; fever), tracheal cytotoxin (damages ciliated cells; cough), lethal toxin (tissue necrosis), Adenylate cyclase (reduces phagocytotic activity), LPS
  • Treatment is only effective if diagnosed in Catarrhal stage
  • Afterwards, it is ineffective and only reduces infectivity
  • New acellular vaccine (against toxins) that is combined with dTap
  • Require 5 doses
  • Vaccination of mothers before birth (since babies have more IgA ABs @ birth)
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15
Q

Mycobacterium tuberculosis

A
  • Bacillus, non-motile, ZN stain
  • Strict aerobe
  • Has mycolic acid in cell wall, allowing it to repel water + stay on dry surfaces for long time
  • Capable of intracellular survival + growth in macrophages
  • No toxin produced
  • Production of cord factor (clumps bacteria together + inhibit phagocytosis; toxic to host cells)
  • Airborne transmission
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16
Q

Tuberculosis

A
  • Caused by Mycobacterium tuberculosis
  • Many latent infections (macrophages)
  • Cell-mediated Immunity
  1. Latent infection (macrophages)
  2. Primary tubercule forms (replication occurs and granuloma attempts to contain it by forming around infection; may calcify)
  3. Spread of active infection (spreads to bloodstream)

Primary infection occurs in the lungs and involve formation of tubercules.

  • Cannot replicate in low O2 + low pH
  • Disseminates to bloodstream if tubercules don’t form or forms + ruptures (miliary infection)

Secondary infection occurs as a result of a direct spread of primary infection or reactivation of a latent infection.

  • Risk factors: presence of another infection, physiological + environmental stress, poor immune sys.
  • Diagnostic tests: Culture (2-3 wks); Tuberculin skin test (only detects memory cells, used for screening); Quantiferon Gold Test (distinguishes latent/active case based on interferon levels produced)
  • Vaccine: BCG (not effective)
  • Treated w/ multiple drug treatments to prevent resistance (6m. to 1 yr)
  • MDR-TB (multiple drug resistance-TB) is resistant to 1st line fo drugs
  • XDR-TB (extreme) is resistant to 1st & 2nd line of drugs
  • Isolation + Quarantine
  • PATIENTS AREN’T INFECTIOUS AFTER 2-4 WKS OF AB TREATMENT
17
Q

Difference between TB Infection and TB disease.

A

Infection = LATENT

  • Presence of MTB
  • (+) Tuberculin skin test
  • Not infectious; no symptoms
  • Normal chest X-ray

Disease = ACTIVE, in lungs

  • (+) Tuberculin skin test
  • Infectious before treatment
  • Chest X-ray shows lesions
  • Symptoms: cough, fever, weight loss
18
Q

What is the BCG vaccine for?

A

Bacillus Calmette-Guerin (BCG)

  • Live culture of Mycobacterium bovis
  • Used for Tuberculosis, especially for preventing Tuberculin meningitis
  • Poor effectivity: short longevity; almost no effect on adults; some effect on children
19
Q

Pneumonia (Pneumonitis)

A

Typical: Streptococcus pneumoniae (encapsulated, facultatively anaerobic, Gram (+) diplococci), penicillin-responsive
Atypical: caused by other organisms; penicillin-resistant
- Causes of pneumonia are different between adults (mainly bacterial) and children (mainly viral)

  • Typical is characterized by rust-colored sputum (blood) and often spreads to blood (sepsis)
  • Vaccines: polysaccharide; conjugate
  • CAPSULE is the main virulence factor (no capsule = no infection)
  • Risk factors: asthma, CF, COPD, weakened immune sys, young children + elderly
20
Q

Bronchiolitis

A
  • Mostly caused by Respiratory Syncytial Virus (RSV; enveloped RNA; direct contact or droplets)
  • Occur in infants after URT + children <2yrs because of their small bronchioles
  • Swollen bronchioles, necrosis of epithelial cells
21
Q

Croup

A
  • Caused by Parainfluenza virus (PIV; enveloped RNA)
  • Common in children
  • Seal-like/barking cough + congestion due to swelling of mucous membranes in RT
  • Obstruction may form because of trachea + larynx structure (non-expandable rings)
  • No antiviral, no vaccine
22
Q

Respiratory Syncytial Virus (RSV)

A
  • Enveloped RNA virus
  • Transmitted via direct contact or droplets (sometimes)
  • Causes life-threatening pneumonia + bronchiolitis
  • Children <5 yr + elderly are most susceptible
  • Epidemic + seasonal
  • Premature babies are at risk for serious disease
  • Given Synagis monoclonal ABs (passive immunization; 1 injection/month for a year)
23
Q

COVID-19

A
  • Enveloped RNA virus (coronavirus family)
  • 4 subtypes: Alpha (common cold); *Beta (human pathogens); Gamma; Theta (animals)
  • Symptoms are heterogenous
  • Severe disease usually presents after 9 days of infection (lymphopenia, increase [plasma] of cytokines + chemokines, increase in clotting)
  • Risk factors: Acute Respiratory Disease Syndrome (ARDs); age; immunocompromised; co-morbid conditions
  • Glycoprotein spikes (S1 binds to host receptors; S2 fuses host cell + viruses envelope)
  • Main receptor: Angliotensin converting enzyme 2 (ACE2), inhibiting ANGII work
  • Treatment: dexamethazone (improve survival), but few antiviral substances found
  • No vaccine or antiviral
24
Q

Influenza A

A
  • Enveloped orthomyxoviridae segmented RNA virus
  • Only “A” has subtypes
  • Symptoms are more severe in smokers
  • Incubation period = 1-5 days
  • Small infectious dose
  • Virus is viable on hard surfaces for 24-48 hours
  • Droplet transmission
25
Q

Pneumocystis jiroveci

A

Yeast

  • Opportunistic pathogen, especially in AIDs, immune-suppressed individuals (transplants)
  • Found in dust
26
Q

Antigenic drift

A

Point mutations in the viral genome encoding for H or N antigens.
- The reason why there are yearly infections, thus need for new vaccines/year

27
Q

Antigenic shift

A

Recombination of the viral RNA segments w/ those from another animal/human.

  • 2 different viruses must infect the same cell
  • Leads to pandemics (every 40 years)
28
Q

Bordetella pertussis

A
  • Aerobic, Gram (-) coccobacillus

- Causes Whooping cough

29
Q

Dimorphic fungal diseases in the lower respiratory tract.

A
  • Histoplasmosis
  • Coccidiodomycosis
  • Aspergillosis

Microbiology (4 decks)

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