URTI's (viruses and bacteria) Flashcards
What is the structure and classification of of the most common cause of the common cold?
• when are you most likely to get it
Structure:
Icosahedral, non-eveloped positive sense single-stranded linear RNA virus
Family:
Picornavirus = family
Fall and Winter - most likely time to get a cold
Will the Rhinovirus ever infect your stomach?
No - Rhinovirus is acid labile so it can’t make it through the GI tract
How is Rhinovirus transmitted and what does it do once it gets there?
Rhinovirus:
• Transmitted via Respiratory Droplets either directly or indirectly by depositing onto the surfaces of the hands then transported by fingers to the nose or mouth. (lack of envelope eliminates the risk of the bug drying out)
Pathogenesis:
• Once it gets there it binds to ICAM-1 (intracellular adhesion molecule 1) on respiratory epithelial cells
• Chemical mediators of inflammation are then released causing vasodilation, mucous secretion, and sneeze and cough stimulation (mediators = Bradykinin and Prostaglandins)
How long is the incubation period for Rhinovirus?
• symptomatic period? what are the symptoms?
Incubation:
• 2-4 days
Symptomatic:
• Sneezing, nasal discharge, sore throat, cough and headache
• MILD CHILLS - but NO SYSTEMIC SYPTOMS for the most part
What is the diagnosis and treatment for Rhinovirus?
Diagnosis = Clinical
Treatment = Supportive
What is the structure of the Corona virus?
• when are you most likely to see this virus?
Helical, enveloped, Postive sense, single-stranded linear RNA
Outbreaks occur in the winter in 2-3 year cycles
Jane presents in January with runny nose, sore throat and a cough. She has been relatively healthy until around 2 days ago when these symptoms onset. She also mentions mild GI distress. What is the MOST LIKELY pathogen?
Corona Virus = likely b/c 15-20% of URTIs are attributable to Corona virus
MOST LIKELY: b/c of GI symptoms (these are NOT associated with Rhinovirus but are associated with corona virus)
Other than the common cold what are some diseases caused by the corona virus?
SARS
MERS
A child presents to the ED with a two week history of having a cold. He now has a persistent (past 3 days) and severe cough that makes a distinct sound “whooping sound” at the end of coughing fits. CXR rules out any Lower Respiratory involvement and their is no evidence of edema in his epiglottis.
• what is the most likely bug?
• what is the physical and genomic structure of this bug?
Most Likely Bug:
• Bordetella pertussis
Physical and Genomic Structure:
• Small coccobacillary, encapsulated gram negative rod
A child presents to the ED with a two week history of having a cold. He now has a persistent (past 3 days) and severe cough that makes a distinct sound “whooping sound” at the end of coughing fits. CXR rules out any Lower Respiratory involvement and their is no evidence of edema in his epiglottis.
• what is the main virulence factor of this bug?
• How does it work?
Bug = Bortedella Pertussis
Main Virulence Factor:
• A-B toxin (pertussis toxin) stimulates adenylate cyclase by catalyzing the addition of ADP-ribosylation (via A unit) to the inhibitory subunit of the G protein complex
- Without inhibition cAMP builds up
- cAMP-dependent kinase (CDK) increases
- This impairs phagocytosis and causes decreased cilia activity
What is the activity of the A and B units in pertussis toxin in Bortedella pertussis?
B unit: binds the cell surface receptor an promotes phagocytosis of the toxin
A unit: catalyzes ADP ribosylation locking the G-protein into the “on” position
A child presents to the ED with a two week history of having a cold. He now has a persistent (past 3 days) and severe cough that makes a distinct sound “whooping sound” at the end of coughing fits. CXR rules out any Lower Respiratory involvement and their is no evidence of edema in his epiglottis.
• how did this kid probably get this disease?
• How contagious is this disease?
Transmission occurs via airborne droplets produced during coughing episodes, its highly contageous
What are the 3 stages of infection of Boretella pertussis (gram -, coccobacillus, CAPSULE) infection?
• what should clue you in that this isn’t Rhinovirus in the earlier stages?
Catarrhal:
• 2 weeks of mild URT symptoms (time of over a week should tell you that its not rhinovirus)
Paroxysmal:
• 2-3 months of sever WHOOPING cough
Convalescent:
• 1-2 weeks of reduction in coughing
A child presents to the ED with a two week history of having a cold. He now has a persistent (past 3 days) and severe cough that makes a distinct sound “whooping sound” at the end of coughing fits. CXR rules out any Lower Respiratory involvement and their is no evidence of edema in his epiglottis.
- What abnormaility (if any) do you expect to see in this kid’s CBC?
- Why is this seen?
• Lymphocytosis - PERTUSSIS (A-B) toxin causes this because it inhibits signal transduction by chemokine receptors, results in failure of lymphocytes to enter lymphoid tissue such as spleen and lymph nodes
How do you diagnose Whooping cough (Bordetella pertussis)?
• Assuming the agar shows a coccobacillary gram -, encapsulated rod, how do you treat?
• How does this treatment vary with age or symptoms?
Culture or do Nasopharyngeal swab (DFA or PCR)
• Azithromycin = Standard treatment - REGARDLESS OF AGE OR WHETHER THEY CONTINUE TO HAVE SYMPTOMS, only exception is you may not want to treat if they’ve experienced symptoms for more than 21 days
