Respiratory Infections Flashcards
1
Q
Dominating bacteria of the respiratory tract.
A
Alpha streptococci
2
Q
Pharyngitis
A
“Sore throat”
- Mostly a viral infection > bacterial > Chlamydia/Mycoplasma > Unknown
- ABs are commonly prescribed, but is infective towards viruses
3
Q
Common Cold
A
- Caused by many different viruses
- No vaccine (b/c it is mild)
- Rhinovirus (30-50%)
- Coronavirus (15-20%)
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)
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
6
Q
Burkitt’s Lymphoma
A
- Associated w/ EBV + malaria endemic areas
- Most common type of childhood cancer in Africa
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
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
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)
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)
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
12
Q
Corynebacterium diptheriae
A
Aerobic, Gram (+) bacillus, non-spore forming
- Most are non-pathogenic, unless lysogenized by bacteriophage
- Causes diphtheria
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)
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)
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
16
Q
Tuberculosis
A
- Caused by Mycobacterium tuberculosis
- Many latent infections (macrophages)
- Cell-mediated Immunity
- Latent infection (macrophages)
- Primary tubercule forms (replication occurs and granuloma attempts to contain it by forming around infection; may calcify)
- 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
Pneumocystis jiroveci
Yeast
- Opportunistic pathogen, especially in AIDs, immune-suppressed individuals (transplants)
- Found in dust
26
Antigenic drift
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
Antigenic shift
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
Bordetella pertussis
- Aerobic, Gram (-) coccobacillus
| - Causes Whooping cough
29
Dimorphic fungal diseases in the lower respiratory tract.
- Histoplasmosis
- Coccidiodomycosis
- Aspergillosis
