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Pharyngitis, Diptheria, and Pertussis
Terms in this set (19)
What are the typical symptoms of pharyngitis?
Sore throat, odynophagia (painful swallowing), Tonsillar enlargement - beefy red with white exudates, anterior cervical lymphadenopathy, fever and chills, headache
What are the common causes of pharyngitis?
Group A Streptococcus pyogenes (GAS), Gonococcal infection, Respiratory viruses - can mimic streptococcal pharyngitis, infectious mononucleosis
Describe Streptococcus pyogenes group A and their virulence.
Streptococcus pyogenes group A is a Gram-positive cocci in chains that is beta-hemolytic, facultative anaerobe.
1) M protein - antiphagocytic, evokes immune response that causes acute rheumatic fever and acute glomerulonephritis. Give it fuzzy surface
2) Capsule of hyaluronic acid
3) Streptolysins O and S - damage cells
4) Hyaluronidase - spreading factor
5) Lipoteichoic acid - adhesin
When you put Strep. pyogenes in blood agar, you see a dense layer of M protein on its surface, why?
Due to the fibrinogen that is in the plasma that binds to the N-terminus of the M-protein (2 alpha-helices that form a coil) as a protection against opsonization.
Epidemiology of streptococcal pharyngitis
Occurs mostly in children (5-15 yr olds). Epidemics usually occur in military recruits. Spread by respiratory droplets from nasal secretions and saliva. Incubation period 2-4 days. Asymptomatic carriage common - these carriers can transmit infection. Symptoms abate in a few days due to immune response - thus, self-limited. In untreated persons organisms persist for weeks. Antibodies develop and protect against same M protein type
How would you diagnose Streptococcal pharyngitis?
Sore throat, odynophagia (painful swallowing), erythema of pharynx, enlarged erythematous tonsils, white exudates on tonsils, cervical lymphadenopathy, fever.
Do a rapid antigen diagnostic test, if negative, do a culture because is it more sensitive
Describe Acute Rheumatic Fever
Major criteria: carditis, polyarthritis, chorea, subcutaneous nodules, erythema marginatum.
Due to immune response to streptococcal pharyngitis, probably mimicry of M protein and heart proteins.
Average interval between pharyngitis and ARF is 19 days.
Penicillin is used for prevention.
In order to get rheumatic heart disease, you must have recurrent heart disease
Caused by the organism Corynebacterium diphtheriae, which is a Gram-positive club shaped rod, non-spore forming, non-motile, no capsule. Its exotoxin is responsible for the disease, a protein that binds to EF-2 to inhibit protein synthesis. The production of exotoxin depends on lysogenic phage, also on slowed bacterial growth due to exhaustion of iron.
What is the epidemiology of diphtheria?
Diphtheria is spread by airborne respiratory droplets and was the leading cause of death in Canadian children 2-14 year olds in the 1920s. Asymptomatic carriage in respiratory tract was an important reservoir for maintenance and spread. Nearly eliminated from U.S. and other countries after 1930 by immunization with formalin-treated toxin, now combined in DTaP.
What is the pathogenesis of diphtheria?
The organism enters, colonizes, and grows in pharynx. Incubation period is 2-4 days. Organism produces exotoxin, which enters epithelial cells where it kills cells by stopping protein synthesis by inhibiting transfer RNA translocase (elongation factor 2). Toxin can be absorbed to reach heart, where it causes myocarditis, or peripheral nerves, where it causes motor and sensory neuropathies.
What are the common symptoms of diphtheria?
Sore throat, tonsillitis, cervical lymphadenopathy, low-grade fever, malaise, formation of membrane on tonsils and pharynx. Bull neck. Mortality 3-12%
How do people die from diphtheria?
Death by asphyxia. There is gray, leathery pseudomembrane that covers the trachea, larynx, and tongue. This is caused by the exotoxin, consists of necrotic epithelium, leukocytes, and bacteria
How would diphtheritic myocarditis look under the microscope?
Myocytes are separated by dense inflammatory infiltrate. s
What is the vaccine for diphtheria?
Inactivated diphtheria toxin, which prevents disease - highly effective to elicit antibodies. May not prevent acquisition of bacteria and carriage. Always combined with other antigens: DTaP -for infants. Td - for adults every 10 years. DT - for children with contraindication for pertussis vaccine.
Describe Bordetella pertussis, which causes whooping cough.
It's a gram-negative coccobacillus, which is aerobic nonfermentative, fastidious and delicate (sensitive to cold and drying) (cotton swab kills). Grows on Bordet-Gengou agar. A PCR test is available. Its adherence is by fimbriae, filamentous hemagglutinin, pertactin. It's secreted exotoxins are: Pertussis toxin - which elevates intracellular cAMP by ADP-ribosylation of a G protein, which activates adenyl cyclase. Adenylate cyclase toxin. Tracheal cytotoxin.
What is the pathogenesis of pertussis?
Tracheitis and bronchitis with accumulation of mucus, inflammatory cells, bacteria, and dead epithelial cells
Intense coughing against closed vocal chords (Valsalva maneuver) attempts to expel mucus which builds up venous pressure sometimes causing hemorrhages in conjunctiva and brain. Leukocytosis - predominance of lymphocytes. Infection rarely extends to lung to cause pneumonia and to ear to cause otitis media, never cause bacteremia.
What actually causes the whoop sound in whooping cough?
Series of short expiratory coughing bursts working to expel mucus, followed by an inspiratory gasp with whoop as air passes turbulently through mucus.
Sometimes there is vomiting and cyanosis after coughing spells. The cough may produce thick mucus plugs. Paroxysms may occur up to 30 times a day, more at night. Child may appear normal and sleep between them.
What is the epidemiology of the whooping cough?
It is highly contagious, usually after exposure due to respiratory aerosol droplets during cough. The vaccine is effective for about 12 years, thus adults are not protected and no maternal antibodies are given. There is a need for an adult booster vaccine.
Describe the pertussis vaccine and treatment
Acellular (no whole bacteria) aP always combined with Diphtheria and Tetanus, thus DTaP. Contains: pertussis toxoid, filamentous hemagglutinin, some with fimbriae or pertactin. The treatment is erythromycin.
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