Lower Respiratory Tract Infections (LRTIs) Flashcards
What microorganism causes tuberculosis?
Mycobacterium tuberculosis (MTB)
Describe the morphology of MTB
Bacillus, non-motile, acid fast (no G), obligate aerobe
What does MTB produce that causes bacteria to clump + inhibits phagocytosis?
Cord factor
Does MTB produce toxin?
No
What forms an impermeable barrier around MTB?
Mycolic acid
What is the major pathogenic mechanism of MTB?
Inflammation
How is TB transmitted?
Airborne
What are the 3 outcomes after TB?
- Latent infection
- Primary tubercle forms
- Spread of active infection
Describe latent infection
TB enters macrophages and remain
Describe primary infection
Host cell isolates the infection in a tubercle (granuloma)
Why can’t TB replicate inside tubercles?
Low pH + low oxygen
When does a disseminated infection (miliary tuberculosis) occur?
If tubercle doesn’t form or if it ruptures
Describe second stage infection
Spread of tubercles from primary infection or reactivation of latent infection
Is MTB present in both TB latent infection and active disease?
Yes
What are the results of a Tuberculin Skin Test for TB latent infection and active disease?
Latent: positive
Active: negative
Describe chest x-ray results for TB latent infection and active disease
Latent: normal
Active: reveals lesion
What are the results of a sputum smear & culture for TB latent infection and active disease?
Latent: negative
Active: positive
Describe the symptoms of TB latent infection and active disease
Latent: none
Active: cough, fever, weight loss
Are TB latent infection and active disease infectious?
Latent: no
Active: infectious before treatment
Are both TB latent infection and active disease defined as cases of TB?
Latent: no
Active: yes
What are the 6 methods of diagnosing TB?
- Acid-fast rods in sputum
- Culture
- QuantiFERON Gold
- Skin test
- Tuberculin test
- Mantoux test
What is the vaccine for TB called?
BCG (Bacillus Calmette-Guerin)
When is BCG used?
High risk children in NA (not effective
Causes of pneumonia in adults are mainly ____ whereas in children are mainly ____
bacterial, viral
What microorganism causes typical pneumonia?
S. pneumoniae
Describe the Gram morphology & characteristics of Streptococcus pneumoniae
Facultatively anaerobic, G+, diplococci
Does S. pneumoniae respond to penicillin?
Yes
S. pneumoniae often spreads to blood, causing:
Bactermia, speticemia, sepsis
What 2 types of vaccine does typical pneumonia have?
- Polysaccharide (23 types)
- Conjugate (13 types)
What are symptoms of typical pneumonia?
Fever, rust colored sputum, breathing problems + chest pain
What are 6 factors that contribute to S. pneumoniae’s pathogenicity?
- Capsule
- Cell wall
- Choline binding proteins
- Autolysins
- Pneumolysins
- Production of OH, neuraminidase, IgA protease
What are the 5 viruses that can cause atypical pneumonia discussed in class?
- Bronchiolitis
- RSV (Respiratory Syncytial Virus)
- Croup
- Covid-19
- Influenza A
What demographic does bronchiolitis affect?
Children <2 years
Describe bronciolitis
- Inflamed bronchioles result in reduced oxygen intake
- Necrosis of epithelial cells
How is RSV transmitted?
Direct contact + droplet
What demographic does RSV affect?
Children <5 years & elderly
What is the treatment for RSV?
None + no vaccine
What are the symptoms for RSV?
Coughing, wheezing
What causes RSV?
Enveloped RNA virus
What causes croup?
Parainfluenza virus (PIV), enveloped RNA
Describe croup
Swelling of mucous membranes in respiratory tract
What demographic does croup affect?
Children
What causes Covid-19?
Sars-CoV-2
What is the main receptor for Covid-19 in humans?
Angiotensin convernting enzyme 2 (ACE2)
ACE2 normally breaks down ____ but when Covid-19 binds to ACE2, ____ is destructive
ANG II, ANG II
What are the glycoprotein spikes on the Covid-19 virus responsible for?
Tropism + attachment to host cell
What is influenza A caused by?
Segmented RNA viruses
How long is the incubation period for influenza A?
1-5 days
How is influenza A transmitted?
Droplet
What is antigenic drift?
- Point mutations in viral genome
- Require new vaccines
What is antigenic shift?
- Recombination of viral RNA segments (significant changes)
- Leads to pandemics
What are 4 fungi that can cause atypical pneumonia?
- Histoplasmosis
- Coccidioidomycosis
- Aspergillosis
- Pneumocystis jiroveci
Does atypical pneumonia respond to penicillin?
No, resistant