Respiratory Infectious Disease Powerpoint Flashcards
What are three mechanisms by which bacteria cause disease?
- Toxin production
- Host immune response
- Bacterial proliferation and invasion
What are three mechanisms by which viruses cause disease?
- Cytopathic effect (viral infection disrupts normal cell physiology which can lead to cell death and disease)
- Host immune response
- Tumorigenesis (viral infection promotes uncontrolled proliferation of infected cells)
What are five features of the respiratory tract that help rid the system of potential pathogens?
- Mucociliary lining of the nasal cavity
- Change in direction of the airway from the sinuses to the pharynx (location of adenoids)
- The ciliary elevator
- Normal flora competition (Staphylococci)
- Alveolar macrophages eliminate microorganisms in the lungs
What are two main obstacles that a microorganisms must overcome in order to initiate infection in the respiratory tract?
- Avoid/survive the mucous layers of the URT which would eventually lead to swallowing the pathogen
- Must also avoid phagocytosis or be able to survive and/or multiply in the phagocytic cell
What pathogens are associated with the Common cold?
Almost exclusively viral infections (many types, Rhinoviruses most common)
What pathogens are associated with Sinusitis?
Bacterial secondary infections (several types, S. pneumoniae and H. influenza are most common)
What pathogens are associated with Pharyngitis?
Viral and Bacterial infections (viruses make up about 90% of the cases here). Important bacterial infections include those of S. pyogenes and C. diphtheriae.
What pathogens are associated with Laryngitis/Croup?
Mostly viral infections (Parainfluenza virus and Respiratory Syncytial virus (RSV)). Associated: Epiglottitis.
How do Rhinoviruses infect the cells lining the nasal passage and the pharynx (initiating cold infection)?
They attach utilizing the intercellular adhesion molecule (ICAM) ICAM-1 of the cells.
What are the features of Rhinovirus?
- RNA virus
- Icosahedral Nucleocapsid
- Nonenveloped
- ss (+) Nonsegmented Genome (Class IV)
- Picornaviridae
What are the two most common causes of community acquired acute bacterial rhinosinusitis infections?
- Streptococcus pneumoniae
- Haemophilus influenzae
What are two other potential bacterial pathogens for Sinusitis (Rhinosinusitis)?
- Streptococcus pyogenes
- Staphylococcus aureus
What are symptomatic treatments for Sinusitis (Rhinosinusitis)?
- Oral hydration w/ nasal saline washes and steam. [This is the one thing that has been proven to shorten the length and severity of infection]
- Acetominophen and decongestants
- Mucolytics
What are antibiotic treatments for Sinusitis (Rhinosinusitis)?
Initial therapy recommendation is Amoxicillin (Augmentin) or Azithromycin (for people allergic to penicillin)
What are the traits of S. pyogenes?
- Bacteria
- Gram (+)
- Cocci
- Catalase (-)
- Beta hemolytic
- Bacitracin sensitive
Certain strains of S. pyogenes can cause scarlet fever. How do they do this?
They secrete certain streptococcal pyogenic exotoxins: ssa, speA and speC
These toxins are superantigens!
What are the traits of Corynebacterium diphtheriae?
- Bacteria
- Gram (+)
- Bacilli
- Non-spore forming
- Non-motile
Why is C. diphtheriae so dangerous?
It produces diphtheria toxin which is an A-B exotoxin. This comes from genes from a lysogenized phase.
What can happen if diphtheria toxin reaches the blood stream?
It can result in myocarditis (heart failure) and neuritis (temporary paralysis of limbs, soft palate and diaphragm)
How do the turbinate bones (“baffle plates”) protect the respiratory system?
Covered in mucus that collects particles not filtered by nasal hairs. The baffle plates cause the air to swirl as it passes over causing a swirling pattern that forces the potential pathogens to make contact with the mucus covering the nasal passages.
Where is the Mucociliary Escalator?
Covers most of the bronchi, bronchioles, and nose. It contains goblet cells.
What are the two basic parts of the Mucociliary Escalator?
- Mucus-producing goblet cells
2. Ciliated epithelium
How does the Mucociliary Escalator work?
It’s a major barrier against infection.
- Cilia are continually beating, pushing mucus up and out into the throat.
- Micro-organisms that could potentially infect the respiratory tract are caught in the sticky mucus and moved up the mucociliary escalator.
What paralyzes the cilia of the mucociliary escalator?
Smoking
What are defenses of the upper respiratory tract?
- Nasal hair
- Ciliary escalator
- Mucus
- Involuntary responses such as coughing and sneezing
- Secretory IgA
What is the normal biota of the upper respiratory tract?
Moraxella, nonhemolytic and alpha-hemolytic streptococci, Corynebacterium and other diphtheroids, Candida albicans. [Also, S. pyogenes, S. pneumoniae, H. influenzae, N. meningitidis & Staph. aureus often present as normal biota]
What are the defenses of the lower respiratory tract?
- Mucus
- Alveolar macrophages
- Secretory IgA
What is the normal biota of the lower respiratory tract?
NONE
In order to establish respiratory tract infection, what conditions must be met?
- There must be sufficient “dose” of microorganisms inhaled in order to establish infection.
- Infectious particles must be airborne.
- Airborne particles must be viable in air.
- Organism must be deposited on tissue susceptible to infection.
- Colonization must occur. (facilitated by adherence factors and immune evasion factors of the pathogenic microorganism)
- Disease symptoms happen.
What usually causes the common cold (rhinitis)? When is it most common? What symptom does it usually not have?
- Rhinoviruses
- Winter months
- Typically does not cause fever
What symptoms are often seen with the common cold (and it’s progression)?
- Starts with nasal stuffiness, sneezing and a headache
- Nasal cavity then fills with fluid (rhinorrhea).
- Tiredness, watery eyes (lacrimation), sore throat, slight fever, and anorexia are common in moderate to severe cases.
- If infection makes it to the lower respiratory tract, there may be a cough
What type of cold is not seen in the winter?
Adenovirus infections can be seen all year round.
How can Rhinitis be spread?
- Person to person
- Hand to hand contact
- Fomites
When do cold symptoms reach their peak?
2-5 days post infection (cells are completely regenerated by day 14 post infection)