Diebel: Micro Respiratory Infectious Diseases 1 Flashcards
How do bacteria cause disease?
- Toxin production–bacteria release toxin that cause illness
- Host immune response- response of host to bacteria that cause illness
- Bacterial proliferation and invasion–growth and spread of bacteria that cause damage that is significant in illness.
How do viruses cause disease?
- Cytopathic effect
- Host immune response
- Tumorigenesis
What is the cytopathic effect?
VIRAL INFECTION disrupts normal cell physiology>
death and disease
What is the host immune response?
Response of HOST to VIRUS>
illness
What is tumorigenesis?
VIRAL INFECTOIN>
uncontrolled proliferation of infected cells
Why is the RT frequently infected?
It is in DIRECT contact w/ the environment>
constant exposure to microorgs in the air
What are infections of the URT?
- Otitis externa
- Otitis media
- sinusitis
- rhinitis (common cold)
- pharyngitis
- epiglottis
- laryngitis/croup
What are LRT infections?
- bronchitis
- bronchiolitis
- pneumonia
What are the anatomic features of the RT that help to ward off potential pathogens?
- mucociliary lining of the nasal cavity
- Change of direction of the airway from the sinuses to hte pharynx (location of adenoids)
- Ciliary elevator
- Normal flora competition (staphylococci)–> block potential colonization event
- Alveolar macrophages (innate)
- IgA secretion into mucosal lining of the airway (adaptive)
What are the 2 main obstacles that microorgs must overcome to INITIATE infection in the RT?
- Avoid/survive the MUCUS LAYERS of the RT> lead to swallowing of pathogen
- Avoid PHAGOCYTOSIS or be able to survive/multiply in a phagocytic cell
What are the baffle plates?
AKA turbinate bones
Covered w/ mucus that collects particles NOT filtered by nasal hairs. Cause air to SWIRL as it passes over FORCING potential pathogens to make contact with the mucus covering the nasal passages.
Where is the mucociliary escalator located?
Covers must of the bronchi, bronchioles and nose.
What is the mucociliary escalator composed of?
- mucus producing GOBLET CELLS
2. CILIATED EPITHELIUM–continually beat and push mucus up towards the throat
What is a major barrier against infection in the respiratory system?
mucociliary escalator!
Microorganisms hoping to infect the respiratory tract are caught in the sticky mucus and moved up by the mucociliary escalator
What does smoking do to hte mucociliary escalator?
PARALYZE the cilia of the mucuciliary escalator
What are the normal biota in the LRT?
NONE!
Considered a sterile environment
What conditions must be met to establish infection?
- sufficient DOSE of pathogen inhaled
- AIRBORNE particle
- VIABLE airborn particle
- Deposited on TISSUE SUSCEPTIBLE TO INFECTION
What are the pathogens of the common cold? Which one is most common?
VIRAL infections
Rhino most common
What are the pathogens of sinusitis? Which ones are most common?
BACTERIAL SECONDARY infections
S. pneumoniae
H. influenza
What are the pathogens of pharyngitis? MC?
Viral AND bacterial
Viral- 90%
Bacterial- s. pyogenes and C. diptheriae
What pathogens cause laryngitis/croup? MC?
MOSTLY viral
Parainfluenza and RSV
Does the common cold cause a fever?
typically NOT
When is a cold most common?
winter months
What are the top viruses that cause the common cold?
rhino
adeno
corona
What is the clinical progression of a common cold? When does a cough appear?
- Stuffiness, sneezing, HA
- Nasal cavity fills w/ fluid
- Tiredness, watery eyes, sore throat, slight fever, anorexia
Cough appears if it moves into the LOWER RT
Is the common cold common worldwide?
YES!
How often do children and adults get colds?
Children (<5)- several per year
Adults- 2-3 per year
How is the common cold spread?
person to person> hand to hand contact
Describe the pathogenesis of rhinovirus?
Inhale infectious droplet>
infects cells lining nasal passage/pharynx by attaching to ICAM-1>
localized inflammation and LYTIC infection>
ciliated epithelial cells are destroyed
When do rhinitis sxs peak?
2-5 days post infection
How long does it take cells to regenerate post rhinitis?
14 days
What happens if a secondary bacterial infection by normal flora occurs post rhinitis?
CHANGE from clear nasal secretions to PURULENT nasal secretions.
SINUS BLOCKAGE can lead to sinusitis or otitis media.
What can cause complications w/ rhinitis?
Infection gains access to lower RT>
bronchitis
What is the treatment for the common cold?
supportive
What is acute rhinosinusitis?
Inflammation or infection of the mucosa of the nasal passages and at least ONE of the paranasal sinuses.
How long does rhinosinusitis typically last?
no more than 4 weeks (self limiting)
What are the 2 MCC of community acquired actue bacterial rhinosinusitis? Other pathogens?
- Streptococcus pneumoniae
- Haemophilius influenze
- S. pygoenes
- S. Aureus
A pt presents with sneezing, rhinorrhea, nasal congestion w/ postnasal drip, aural fullness, facial pressure, HA, sore throat, cough, fever and muscle aches. What may they have?
Rhinosinusitis
What can a Viral URI predispose you to?
Secondary bacterial infection
When might you diagnose a fungal sinusitis?
RARE but can be identified if antibacterial drugs FAIL to clear a sinus infection.
What is the MCC of fungal sinusitis?
Aspergillus fumigatus
How long does it take sinusitis to resolve?
5-7 days
usually without medical treatment
What type of infections can follow the common cold, dental extractions and rhinitis d/t allergies?
Bacterial sinus infections
If an ADULT pt has moderate sxs of rhinosinusitis that persists BEYOND 7 DAYS or severe symptoms of any duration that include FACE SWELLING OR TOOTH PAIN, what might you diagnose?
Acute bacterial rhinosinusitis
When might you diagnose acute bacterial rhinosinusitis in children?
Moderate sxs of rhinosinusitis that last LONGER THAN 10-14 DAYS or when there are severe sxs of any duration that include a FEVER >102 W/ FACIAL PAIN/SWELLING.
How do you treat viral rhinosinusitis?
symptomatic treatment
What treatment is recommended for bacterial rhinosinusitis?
Antibiotic–start w/ broad spectrum
What are symptomatic treatments for sinusitis?
- oral hydration w/ nasal saline washes
- acetaminophen and decongestants
- mucolytics
What is the initial antibiotic therapy recommended for sinusitis?
amoxicillin (augmentin)
azithromycin
What causes most sore throats?
VIRUSES
90% in adults
75% in children
What is the MC bacterial cause of acute pharyngitis?
s. pyogenes
If a pt presents w/ fever, sore throat, edema and hyperemia of the tonsils and pharyngeal walls you would suspect…
Pharyngitis
What sxs of pharyngitis suggest a viral cause?
Conjuntivitis cough hoarseness inflammation of mucus membrane diarrhea
How do pts w/ pharyngitis caused by s. pyogenes present?
Fever
severe pain upon swallowing
SUDDEN onset
maybe HA, N and V, and abdominal pain
How do you confirm a suspected s. pyogenes infection?
RAPID strep test is required (detect surface ag of bacterial cells in back of throat)
How do you treat s. pyogenes pharyngitis? Why?
antibiotics to BLOCK the develoment of glomerulonephritis and RF
w/in the 9 days of the first sign of infection
Pharyngitis d/t s. pyogenes is commonly seen in what demographic?
Children 5-15
How does pharyngitis spread?
person to person contact
What is the pathogenesis of viral pharyngitis?
Virus gains access to mucosal cells lining nasopharynx>
replicates>
damages host cells at sites of replication
Describe the pathogenesis of bacterial pharyngitis?
S. pyogenes attaches to mucosal epithelial cells using M PROTEIN, LIPOTEICHOIC ACID AND FIBRONECTIN BINDING PROTEIN (protein F).
What prevents phagocytosis of s. pyogenes?
Capsule made of hyaluronic acid
What invasion factors are associated w/ s. pyogenes?
protease and hyaluronidase
What is the treatment for pharyngitis?
Supportive for all cases
viral- acetaminophen and warm saline gargles
How do you treat s. pyogenes infections?
penicillin G or erythromycin (if allergic to penicillin)
How does s. pyogenes cause scarlet fever? What encodes the exotoxins?
Secretes streptococcal pyogenic exotoxins (SpeA, SpeB, SpeC and SpeF). These toxins are superantigens.
Lysogenized bacteriophage (NOT hte bacteria itself)
Who is most at risk for scarlet fever? What sxs are indicative of scarlet fever?
Children
Strawberry tongue and full body rash
What is the difference between staph and strep in terms of response to H202?
Staph- uses catalase to break O2 into water
Strep- uses peroxidase to break O2 into water
What is Diptheria toxin? What happens if it reaches the blood stream?
AB EXOTOXIN that comes from genes of a LYSOGENIZED PHAGE.
Myocarditis (HF) and Neuritis (temporary paralysis of hte limbs, soft palate and daiphragm)
How does Diptheria use the AB exotoxin to infect cells?
B binds surface of host cell>
Allows A to gain access to host environment>
A acts against EF2>
blocks ability of cell to translate protein>
cell death
A child presents w/ fever, restlessness and SOB. What might they have?
Croup
How does croup usually progress?
Mild URI w/ cold-like sxs, nasal congestion, sore throat and cough that lasts 2-3 days.
Followed by harsh BARK LIKE cough
When does respiratory stridor usually occur in a child w/ croup?
At night
What are sxs of severe croup?
Inspiratory stridor at rest w/ nasal flaring
Suprasternal and intercostal retractions
Hypoxemia> lethargy/agitaiton
When do croup sxs usually peak and resolve?
Peak- 3-5 days
Resolve 4-7 days
How do you spread croup?
person to person contact
What age children are most susceptible to croup?
6 mos to 3 years
Boys
When does croup usually occur?
late fall and early winter
Why are giant multinucleated cells often seen w/ RSV?
F proteins on surface of virus cause cell membranes on nearby cells to fuse
A woman presents with a runny nose, sneezing, an irritable throat, and a slight fever. She suffers similar symptoms every year, often at the same time as other members of her family. Her symptoms go away within a week, except for the nasal discharge that persists for a few more days.
Common Cold
A father brings his baby girl to the ED in the middle of the night. Before leaving the house, the girl had a high fever, nasal discharge, and a barking cough. Now, however, the barking cough seems to have disappeared. The doctor on call realizes that the cool night air probably relieved the child’s symptoms before she arrive at the hospital. Because no inspiratory stridor is noted on physical exam, the doctor sees no need to give the girl corticosteroids and assures the father that the illness will go away in a few days.
Croup- RSV
A young immigrant girl (suspect vaccination schedule) goes to the doctor complaining of a sore throat and difficulties in swallowing and breathing. Her voice is unusually nasal and a large gray mucous film is noticed on the oropharynx. The patient also exhibits a slight paralysis on her tongue. Her blood pressure is low. Her physician begins immediate treatment and orders a potassium tellurite culture to confirm his worst suspicions.
Diptheria
How do you prevent diptehria?
DTap and TDaP vacine
How do you treat diptheria?
antitoxin PLUS penicillilin or erythromycin
What is indicative of bacteria on an agar plate?
Corynebacteria can reduce potassium tellurite (K2TeO3) to elemental tellurium (black).
A 8-year-old child had a sore throat, difficulty swallowing, and fever for 5 days. Examination was remarkable for fever; and an extensive red rash on the neck, groin, armpit (axillae). A bright red lingual papillae superimposed on a white coat (Strawberry tongue), exudative tonsillitis and cervical lymphadenopathy
Scarlet Fever- s pyogenes
If you see a culture w/ beta hemolysis w/ bacitracin sensitivity you know its…
s. pyogenes
