RHS07 - Respiratory Tract Infections 1 Flashcards
List the two primary types of respiratory invaders and key characteristics that they possess.
- Professional (primary) Invaders - are able to infect a healthy RT. Generally possess specific properties for evading host defenses
- Secondary Invaders - cause diseases when host defenses are already impaired
Primary Invaders can also be Secondary and Secondary can also be Primary.
List the primary factors that damage the RT’s normal defenses.
- Smoking - impaired ciliary function, increased mucous volume
- Endotracheal Intubation - mucosal injury, impaired ciliary function, site of attachment
- Pollution - induces inflammation
- Suppression of cough reflex - aspiration
- Predisposing Infection - upregulation of receptors, setting for a secondary invader
- Disruption of Homeostasis - age, malnutrition, immunosuppression, underlying disease, etc.
Describe the essential difference between a pathogen that is transmitted via droplets or can be aerosolized? How does a pathogen become aerosolized.
- A pathogen that can be aerosolized can survive dehydration
- Respiratory droplets (from cough/sneeze) are largely mucus which is has a large amount of mucin. Mucin is a highly glycosylated peptide that can hold 600x its weight in water. When someone sneezes or coughs, the droplets rapidly evaporate, leaving behind a dried flake of mucin, salts, IgA and microorganisms adhering to it. These flakes can be held aloft indefinitely.
What is the cause of most endogenous RT infections? How does this usually happen?
- Movement of the normal flora from the URT to the LRT
- This can be a result of old/very young age, a preceding infection (COPD, CF, asthma), smoking, aspiration
What is aspiration pneumonia and how can it be identified?
Aspiration pneumonia is pneumonia caused by aspiration. It can be identified by a culture revealing a mixed flora (aerobic, anaerobic, gram positive, and gram negative) which is the flora present in the URT
List the different ways a virus can affect a host cell.
- Transform it into a tumor cell
- Lysis
- Persistent Infection - slow release of virus w/out cell death
- Lysogenic Infection
- Syncytial Formation - the infected cell fuses with another cell, eventually forming a giant cell called a syncytium
What is the common cold AKA? During what time of year does it usually happen? How is it most commonly transmitted?
- AKA - rhinitis, nasopharyngitis, rhinopharyngitis
- Can happen anytime but most commonly seen in fall and winter
- Transmitted via droplets
- Air droplets from sneezing, coughing, or blowing nose
- Fomite contamination through touching nose, eyes, or mouth
What pathogens are the most common cause of the common cold?
- Rhinoviruses, Coronaviruese, Adenoviruses
- Enteroviruses - coxsackievirus, echovirus
- RSV
- EBV
- HPIV
- Human metapneumovirus (hMPV)
- Bocavirus (in children)
What are the most common symptoms of the common cold?
- Nasal congestion
- Runny nose
- Scratch throat
- Sneezing
- Adults/Older Children may have a low fever (or not)
- Young children often run a 37.7C-38.8C fever
List the seasons and the common cold pathogens most commonly found during those seasons.
- Winter - adenovirus, coronavirus, influenza, MPV, RSV, Strept (group A)
- Spring - adenovirus, coronavirus, MPV, PIV-3, rhinovirus, RSV, Strept (group A)
- Summer - adenovirus, enterovirus, MPV, PIV-3, PIV2,3, rhinovirus
- Autumn - adenovirus, MPV, PIV2,3, RSV, Strept (group A)
Which pathogen causes the most common cold cases? What is its incubation period?
Rhinovirus
48-72 hrs
What is rhinovirus AKA? What family are these viruses from?
- AKA - RhV and HRV (Human Rhinovirus)
- Family: Picornaviridae (small rna virus)
What are the complications rhinovirus can cause?
- Exacerbation of asthma and COPD
- Secondary infections of sinuses and middle ear
- LRTIs in young children and immuno-compromised adults
What is the pathogenesis of rhinovirus?
- 90% of rhinovirus binds to ICAM-1 (intercellular adhesion molecule) to infect a host cell. 10% bind LDLR
- Once infected, the epithelium becomes inflamed and beings releasing NO, VEGF, and EGF
- NO, VEGF, and EGF cause the surrounding muscle to release matrix proteins which remodel the airway
