Chapter 12 Flashcards
What are the parts of the upper respiratory tract?
Epiglottis, larynx, nasal cavity and pharynx
What is the preferred area of infection for coronaviruses and rhinoviruses?
Nasopharynx
What types of respiratory infections are restricted to the surface?
Common cold, influenza, streptococci in throat, chlamydia, diphtheria, pertussis and thrush
What is the common cold (rhinitis) caused by?
Many different types of viruses, mostly rhinovirus and coronaviruses
What are characteristics of pathogens that are good at infecting the respiratory tract?
less than 5 microns (very small, aerosoluble), Gram + so it doesn’t clump together
Adhesion to normal mucosa, interfere with cilia, resist destruction by macrophages, damage local tissues
What does it mean to be a secondary invader?
Infect when host defences are impaired
What types of respiratory infections spread throughout the body?
Measles, mumps, rubella, EBV, CMV
How is the common cold transmitted?
Aerosol or virus contaminated hands
What is a symptom of the common cold?
A flow of virus rich fluid (rhinorrhea) from the nasopharynx (if green, bacterial infection), sneezing
How can we treat the common cold?
Self-limiting, symptomatic treatment. No vaccine due to antigenic diversity of viruses
What makes a professional invader?
The ability to infect a healthy respiratory tract. Opens up the tract to secondary infection
What are pharyngitis and tonsillitis caused by?
70% by viruses like adenovirus, Epstein-Barr virus and cytomegalovirus
Bacterial by S. pyogenes (white pustules in pharynx)
What is cytomegalovirus (CMV) infection characterized by?
Multinucleated cell formation and/or intranuclear inclusion in humans
How does EBV infection progress?
Immunologically mediated
Virus replicated in epithelial cells and B lymphocytes (CD21), spreads to B cells in local lymphoid tissues (lymph nodes and spleen) and the T cells respond to the infected B cells
What is the clinical presentation of EBV infection?
Infant/young child show no clinical disease
Young adults get infectious mono/glandular fever 4-7 weeks after initial infection, fever, sore throat, petechiae (red spots) on hard palate enlarged lymph nodes, hepatitis
Spontaneous recovery but saliva will be infectious for months and remain latent
Where does CMV localize?
In the epithelial cells of salivary glands (saliva), kidney (urine), cervix (secretions) and testes (semen) and will shed for months
How does CMV become a successful pathogen?
Poor target for cytotoxic T cells as they interfere with transport of MHC-1 molecules to cell surface and induce expression of Fc receptors on cell surface
What are the symptoms of CMV infection?
Infant/child will show no symptoms
Adolescents will have a glandular fever-type illness (fever, lethargy, abnormal lymphocytes, mono)
Adults will have mild illness
Primary infection during pregnancy will spread to fetus and reactivate causing mental retardation in the baby.
What causes mononucleosis?
Epstein-Barr Virus (EBV) from exchange of saliva
Which age groups are most susceptible to EBV?
1-6 years and 14-20 years
What are the symptoms of bacterial pharyngitis?
Sore, red throat, difficulty swallowing, sudden fever, scarlet fever (sandpapery rash, strawberry tongue, systemic)
What are some complications of s. pyogenes?
Rheumatic heart disease, acute glomerulonephritis (circulating immune complex deposits in glomeruli, activating complement and coagulation systems, infalmmation, blood in urine) and rheumatic fever (fever, joint pain, swelling)
What are the symptoms of EBV infection?
Cytokine release, the infected B cells become polyclonally activated and produce autoantibodies (IgM, erythrocytes)
How does infection with the mumps virus progress?
Virus goes into lymph nodes, spreads via circulatory system to salivary glands, ovaries
Long incubation time
Recovery in one week with lifelong immunity
What are the cancers associated with EBV? What are their co-carcinogens?
Burkitt’s lymphoma in Africa and Papua New Guinea. Co-carcinogen with malaria (weakens T-cell control of EBV infection)
Nasopharyngeal carcinoma in China and SE Asia. Co-carcinogen is ingested nitrosamines (preserved fish)
What causes bacterial pharyngitis?
Streptococcus pyogenes
How is bacterial pharyngitis treated?
Penicillin unless resistance is presence. Vaccine available
What causes parotitis (inflammation of parotid glands-largest salivary glands)?
Mumps virus spread by airborne droplets and close contact
How do infection with the mumps virus progress?
Recovery in one week with lifelong immunity
What are some complications of the mumps virus?
Meningitis, encephalitis, pancreatitis and hearing loss
What is the vaccine for mumps virus?
MMR
Autism controversy
What is otitis media (middle ear infection) caused by?
50% viral
S. pneumoniae, H. influenzae, S. pyogenes, M. catarrhalis, S. aureus
The outcome of a respiratory tract infection
Who is otitis media most commonly found in?
Preschool age patients due to wider Eustachian tube
What are the clinical manifestations of otitis media?
Early in children with have fever and irritability
Late infection has ear pain, changes in hearing and purulent discharge (accumulation of fluid and inflammation)
What are some complications of otitis media?
Tympanic membrane damage leading to hearing loss
How is otitis media treated?
Using empirical therapy. Wait for 1 week before giving antibiotics in case it may be viral
How is a pathogen successful in causing otitis media?
Avoids cleansing by the epithelial cilia
What is otitis externa caused by?
Different pathogens from otitis media, similar flora to skin
Staphylococcus aureus, Candida albicans, Pseudomonas aeruginosa
What is otitis externa treated by?
Antibiotic ear drops
What is acute sinusitis caused by?
Similar pathogens to otitis media
Prolonged RTI
What are the symptoms of acute sinusitis?
Facial pain, purulent nasal discharge, fever
Headache and upper teeth pain in maxillary sinusitis
What are the complications of acute sinusitis?
Orbital cellulitis, osteomyelitis, meningitis, brain abscess
What causes epiglottitis?
H. influenzae
What are the clinical manifestations of epiglottitis?
Edema and inflammation of the epglottis causing airway blockage
Medical emergency
