Microbiology Of URI's Flashcards
Normal protective body mechanisms against URI/LRIs
Mucocillary apparatus
Dendritic cells (DCs)
Alveolar macrophages
IgG
Compliment
Surfactant
Mucocillary apperatus specifics
Mucus traps pathogens in the respiratory system and either brings it down to the stomach or cough it out via the cough reflex
Mucus also contains enzymes and IgA which degrade bacteria an provide a bacteriostatic environment to most pathogens
Dendritic cell specifics
Sense and catch pathogens and bring them to draining lymph nodes to activate adaptive immune responses
Alveolar macrophage specifics
Catch particles in the lower respiratory tract that managed to avoid all other defenses
- phagocytize them
- also secrete ROS and bacteriocidal enzymes
- synthesis cytokines
Are primary phagocytes of the innate immune system
Common virus agents in the upper respiratory tract infections
Adenovirus
Rhinovirus
Parainfluenza virus
RS virus
Coxsakie virus
Common Bacterial pathogens that infect them upper respiratory tract
GAS
GCS
Gonorrhea
Diphtheria
Chlamydia
Rhinitis
Infection of the nasal cavity
- produces variable cold like symptoms
Most common symptoms are:
- nasal stuffiness
- sneezing
- runny nose
- sore throat
Pathogenesis
1) Virus attachment initiates viral replication
2) Lysis cells once replication is complete
3) lysis of cells spreads to other respiratory cells causing destruction and further infection
What are the most common infections of the nasopharynx?
Virus pathogens
- rhinoviruses and coronavirsues make up 50%
Very rare for bacterial but still possible
Rhinoviruses
MOST COMMON CAUSE OF COLDS
Are small, un-enveloped viral particles
- single-stranded (+)-sense RNA
- optimal temp = 33C
Replicates and spreads locally as well as is shedded in nasal secretions
Secretory IgA is the prime mover in destroying the virus
- also develops the symptoms
Location of rhinovirus in people who are infected
1) hands (why washing hands is sooo important)
2) nose
3) saliva
Bacterial pharyngitis vs viral pharyngitis
Bacterial:
- medical intervention needed
- swollen uvula
- swollen lymph nodes w/ white spots
- gray furry tongue apperance
- throat redness
- this is usually strep throat
- GAS or GCS are causative agents
Viral:
- self-limiting and home care only
- swollen tonsils w/out white spots
- throat redness
- almost always shows w/ additional nasal issues
- most commonly a rhinovirus
- can also be coxsackie, EBV or RS viruses
Herpangina vs hand/foot/mouth disease
Both are caused by coxsackie viruses
Herpangina:
- Group A coxsackie virus
- abrupt onset of fever
- sore throat w/ cold sore looking lesions on soft palate
- dysphagia and malaise
- may show vomiting also
- most common in children between 1-7 yrs
Hand/foot/mouth
- generalized coxsackie virus
- almost exactly like herpangina except also produces the following
- skin rashes
- blisters on hand and feet
- also usually affects children 1-7
Epstein Barr virus
Member of herpes
- replicates in oropharyngeal epithelial cells
- transmits via saliva and local infection in the mouth/pharynx and larynx
- disseminates through the body via the reticuloendothelial system and often infects B-cells
Almost always is asymptomatic in innate/latent phase
Reactivating phase produces most of the symptoms of mono
- fever
- lymphadenopathy primarily posterior regions
- severe malaise
- sore throat
- only differ enforcement between this and mono symptom wise is the lymphadenopathy is anterior and splenomegaly is often reported*
Most common in the following 2 age groups
1) children between 1-6
2) young adults between 14-20
Primary EBV infections pathogenesis
Infects B-cells eventually and triggers abnormal replication
- produces heterophile antibodies (non-specific IgM antibodies) which go on to destroy and target RBCs and other tissues
- heterophile antibodies are tested via direct agglutination of multiple blood samples (will bind to all)
Clinical symptoms arise based on T-cells activating in response to the abnormal B-cells
After “curing” EBV established a latent infection in memory B-cells and their future generations
- this allows virus to become reactivated in the future if it is triggered properly
Types of antibodies specific to EBV and the stage at which they are the most prevalent
Anti-EBV IgM
- most prevalent in incubate/acute phases
Viral capsid antigen IgG
- most prevalent in acute and convalescence stages
Anti-EBV IgG (EA-D IgG)
- most prevalent in acute phase
Anti-EBV IgG (EBNA-1 IgG)
- most prevent in the convalescence stage
How to diagnose EBV from testing
obviously clinical presentation must match first
Lab results
- atypical lymphocytes (abnormal appearance with bleeding of the cell membrane)
- presence of heterophile antibodies
- presence of specific EBV antibodies
- liver function tests show high liver enzymes
note if > or = 10% atypical lymphocytes are present in blood smears, it is diagnostic of mono
