Upper Respiratory Infectious Disease I (Zimmer) Flashcards
How do bacteria cause diease?
- Toxin production
- host immune response
- bacterial proliferation and invasion
How do VIRUSES cause disease?
- cytopathic effect - disrupts normal cell physiology
- host immune response
- tumorigenesis
5 things that help rid the respiratory tract of potential pathogens
- mucociliary lining of the nasal cavity
- contains lysozyme, lactoferin and secretory IgA antibodies
- Change of direction of airway from sinuses to pharynx
- alveolar macrophages - found in lungs
- ciliary elevator
- normal flora (staphylocci)
What are the 2 main obstacles that an organism must overcome to cause infection in respiratory tract?
- Avoid/survive mucus layers of URT - leads to swallowing of pathogen
- avoid phagocytosis or be able to surivive and or multiply in phagocytic cell
Explain how swirling of air prevents pathogen invasion
turbinate bones are covered with mucus and they collect particles that arent filtered by nasal hairs. Bones cause air to swirl as it passes over that forces the potential pathogens to make contact.
Where is the mucociliary elevator found?
What is it composed of?
what can paralyze the cilia of it?
- found in the bronchi, bronchioles and nose
- composed of:
- mucus producing goblet cells
- ciliated epithelium
- smoking can paralyze
What conditions must be met to establish a respiratory tract infection?
- there must be sufficient dose of microorganisms inhaled in order to establish an infection
- infectious particles must be airborne
- airborne particles must be viable in the air.
- organism must be deposited on tissue susceptible to infection in the host.
List 4 common URI diseases and the common associated pathogens:
- common cold - mostly viral - rhinoviruses common
- Sinusitis - Spneumoniae, H. influenza
- Pharyngitis - viral + bacterial (S. pyogenes, C. diptheriae)
- Laryngitis/Croup - mostly viral (Parainfluenza, RSV)
Common Cold (rhinitis)
Causative bugs?
when does it occur?
Symptoms:
Spread?
- caused by rhinoviruses > coronaviruses > adenoviruses
- more often in winter (except adenovirus)
- Symptoms
- nasal stuffiness, sneezing headache
- fluid in nose, tired, watery eyes, slight fever, scratchy throat, anorexia
- cough if lower respiratory
- Spread = hand to hand or through other objects
Common cold (rhinitis)
how does virus infect?
What are complications?
Diagnosis
Treatment
- virus infects nasal passages following direct contact of surfaces or inhalation of infectious droplets
- complications
- secondary bacterial infection, sinusitis, otitis media, bronchitis
- diagnosis based on symptoms + time of year
- supportive therapy
How does rhinovirus infect the nose?
infects cells of nasal passages and pharynx after attaching using ICAM-1
ciliated epithelial cells are destroyed by local inflammation and infection.
inflammation causes exudate and increased ICAM expression
exudate can block passages which can lead to sinusitis.
symptoms peak 2-5 days.
Rhinovirus
Type of virus
capsid
envelope
genome
family
- RNA virus
- icosahedral nucleocapsid
- NON enveloped
- ss+ class IV
- picornaviridae
40-50% of common cold
Coronavirus
Type of virus
capsid
envelope
genome
family
- RNA
- helical
- enveloped
- ss+ - Class IV
- coronaviridae
10% of colds
influenza virus A, B, C
Type of virus
capsid
envelope
genome
family
- C is more cold symtpoms not flu
- RNA virus
- helical
- enveloped
- ss (-) Class V genome segmented
- Orthomyoxviridae
Coxsackie A and B
Type of virus
capsid
envelope
genome
family
- RNA virus
- icosahedral
- NON enveloped
- ss+ Class IV
- picornavirdiae - enterovirus
Paramyxovirus (Parainfluenza)
Type of virus
capsid
envelope
genome
family
- RNA
- helical
- enveloped
- ss- Class V nonsegmented
- paramyxovirdiae
Adenovirus
Type of virus
capsid
envelope
genome
family
- DNA virus
- Icosahedral
- NON enveloped
- DS linear DNA (group I)
- Adenoviridae
What 3 bugs are the most common cause of conjunctivitis?
- H. influenza
- Adenovirus
- S. pneumoniae
Acute Rhinosinusitis
Symtpoms
Length
of cases
- inflammation or infection of mucosa or nasal passage and at least one paranasal sinus that lasts no longer than 4 weeks
- > 11 million cases each year
- sneezing, rhinorrhea, nasal congestion w/postnasal drip, aural fullness, facial pressure, headache, sore throat, cough, fever, muscle aches
- VIRAL URI predisposes
What is the most common cause of sinusitis and how long should it last?
viruses - 5 to 7 days.
when is bacterial sinus infection more likely?
How can we tell?
- follows common cold, dental extractions, rhinitis due to allergies
- Adults
- symptoms > 7 days
- facial swelling
- tooth pain
- Kids
- lasts longer than 10 to 14 days
- fever > 102 w/ pain + swelling
What are the most common causes of acute bacterial rhinosinusitis infections?
- Streptococcus pneumoniae
- Haemophilus influenza
What are other potential sinusitis bugs that aren’t as common?
- Streptococcus pyogenes - also pharngitis
- Staphylococcus aureus
- Moraxella catarrhalis
What is typically seen if antibacterial drugs fail to clear the sinus infection?
- fungal infection
- most common is aspergillus fumigatus
- immunocompromised patients must have the fungal pathogen removed.
What are symptomatic and antibiotic treatments for sinusitis?
- symptomatic
- oral hydration - nasal saline washes + steam
- Acetaminophen and decongestants
- Mucolytics
- Antibiotic treatment
- amoxicillin (Augmentin)
- Azithromycin
Pharyngitis
common when
most common cause
spread
- winter and spring
- viruses
- spread person to person or contaminated object contact
What is the most common bacterial cause of acute pharyngitis?
Streptococcus pyogenes
kids are 60-75% viral
adults are 90% viral
How is viral pharyngitis initiated?
Viruses gain access to mucosal cells of nasopharynx. Replication occurs. Damage to host cells is common.
How does strep pyogenes initiate bacterial pharyngitis
attaches to mucosal epithelium using M protein, lipoteichoic acid and fibronectin binding protein (protein F)
What does strep pyogenes have that prevents phagocytosis by macrophages
capsule compsed of hyaluronic acid (HA)
What are strep pyogenes virulence factors for invasion
protease
Hyaluronidase
Common symptoms of viral and bacterial pharyngitis
Fever, sore throat, edema, hyperemia of tonsils
Suggestive of viral cause of pharyngitis
- Conjunctivitis
- Cough
- Hoarseness
- Inflammation of mucus membranes
- Diarrhea
What may you see if it’s bacterial pharyngitis?
- fever
- severe pain on swallowing (sudden onset)
- headache
- nausea
- vomiting
- abdominal pain
- red tonsils w/o exudate and enlarged cervical lymph nodes
How should strep pyogenes be diagnosed and treated?
- rapid strep test - antigen detection
- Antibiotics
- peniciilin
- erythromycin
- need to block development of glomerulonephritis and rheumatic fever
- cultures = more accurate but take 1-2 days to complete
Streptococcus pyogenes
Gram stain
shape
catalase
hemolysis
sensitivity
- gram pOSITIVE
- cocci
- catalase NEGATIVE
- BETA hemolytic
- BACITRACIN sensitive
What do strains of strep pyogenes have that can cause scarlet fever?
What do you see clinically?
- secrete exotoxins ssa, SpeA and speC
- these are superantigens - activate T cells non specifically and cause major cytokine release.
- see strawberry tongue w/white appearance and w/red spots
What are 2 ways aerobic or aerotolerant bacteria can get rid of oxygen free radicals
- peroxidase
- catalase
What is the causative organism for hoarsenss, sore throat, swollen lymph nodes, fever, nasal discharge, malaise, rapid breathing + THICK GREY MEMBRANE ON BACK OF THROAT
Diphteria - cornyebacterium diptheriae
Cornyebacterium diptheria
Gram stain
shape
spores?
motile?
- gram POSITIVE
- bacilli
- NON spore forming
- NON motile
What is the virulence of C. diphteriae
has A-B toxin
A- active, B-binding
inhibit elongation factor
What are the classic presentation of croup
- bark-like cough
- fever 100.4 to 102.2 F
- restless
- SOB
- follows URI
- respiratory stridor at night - can wake patient
Croup
common in?
common when?
spread
- young children 6 months to 3 years
- more common in boys
- late fall and early winter
- spread person to person contact
- self limiting - treat symptoms unless severe
- corticosteroids and nebulized epi
- oxygenation w/ventilation support in severe respiratory distress
what are complications of croup?
- crusty exudates form - airway obstruction
- segmental ateleactasis
- pneumothorax
- ostructive mediatinal emphysema
- bronchopneumonia
What are the most common causative agents of croup.
- Parainfluenza virus (any time)
- Influenza virus (winter/early spring)
- Respiratory syncytial virus (winter/early spring)
RSV
Type of virus
capsid
envelope
genome
family
- virus
- helical
- enveloped
- ss - nonsegmented linear (class v)
- paramyxoviridae
- pneumovirus
most common cause of pneumonia in young children as well
What is seen with RSV?
multinucleated cells that result from multiple cell fusions of uninuclear cells
have F proteins that cause cell membrnaes to fuse
Epiglottitis
Common?
occurs in
Cause
- very rare compared to croup
- .97 to 3.1 cases per 100,000
- life threatening
- occurs in CHILDREN
- beta hemolytic streptococci - group A more frequent, B or C.
- haemophilis influenza type b
What is the treatment for epiglottitis?
- secure airway
-
broad spectrum 2nd or 3rd gen cephalosporin WITH penicilinase-resistant pencillin
- used as EMPIRIC THERAPY
How can you compare it to croup - distinguishing factors between epligottitis and croup
- Onset is SUDDEN
- DROOLING IS PRESENT
croup has a more gradula onset.
may also see severe dysphagia and high fever
How should we treat diptheria?
antitoxin + penicillin
arythromycin
What is a potassium tellurite culture for?
determining if it’s diptheria - cornebacteria can reduce tullurite to elemental tellurium which turns it black
T/F. After a rhinovirus infection, the individual acquires IgA immunity
True
Explain how parainfluenza virus infects
uses hemagglutinin (HA) envelop protein w/sialic acid to get endocytosed.
neurominidase (NA) envelope protein cleaves HA bound to sialic acid for viral spread
What is a coronavirus that causes rapidly progressive viral pneumonia with fever, dyspnea, and cough. Could lead to respiratory failure and death.
SARS
Why is influenza C less virulent?
there is no animal reservoir so there is no antigenic shift
What does the immune response produce when infected with bugs, like influenza C?
IL-1 and IFN-gamma
How can you diagnose influenza C?
Can culture nasopharyngeal swab and dtect HA type via RBC agglutination
What are some strep pyogenes virulence factors that contribute to spread of infection
streptokinase (plasminogen to plasmin)
M protein (resists phagocytosis)
hyaluronidase (breaks down CT)
DNase (breaks down DNA)
Strep pneumonia
hemolyiss
susceptible to
positive for what?
alpha hemolytic
optochin sensitive
quelling rxn
Hamophilus influenza type B
gram stain
growth on agar
tests
Gram negative
needs hemin (X factor) and NAD (V factor) on chocolate agar.
+ quelling test
Treatment for RSV
usual.
Severe caes.
Preventive
- usual = supportive
- severe = albuterol, aerosolized ribavirin
- Preventative
- synagis (F antigen vaccine)
- used in high risk infants - premature, lung disease, heart disease
