Pharyngitis
Causative agents
Common
-
Acute pharyngitis, whether febrile or not, is generally caused by
viruses.
-
In enteroviral infection (herpangina)
- adenovirus infection (pharyngoconjunctival
fever)
-
Epstein-Barr virus infection (infectious mononucleosis)
- Group A B-hemolytic Streptococcus is the only common bacterial causative
agent and except during epidemics it accounts for probably fewer than 15% of
cases.
Rare
- Mycoplasma and Arcanobacterium hemolyticum
-
Corynebacterium diphtheria
- M mixture of anaerobic bacteria and spirochetes
-
Neisseria
gonorrhoeae infection
Causative agents of exudative pharyngitis
- Group A streptococcus (Scarlet fever)
- Arcanobacterium hemolyticum
- Corynebacterium diphtheria
- Anaerobic pharyngitis (vincents angina)
- Adenovirus
Agents that cause exudative pharyngitis associated with
rash
- Group A streptococcus (Scarlet fever)
- Arcanobacterium hemolyticum
- Espstein-Barr Virus
When to suspect rare etiology
- Mycoplasma
- Associated with pneumonia
-
Corynebacterium diphtheria
-
unimmunized
-
low socioeconomic groups
- Membrane in throat
- Anaerobic bacteria and spirochetes
-
Neisseria
gonorrhoeae infection
- Sexually active age group
- Homosexuals
Transmssion
-
The common etiologic agents are spread by respiratory droplets and via
contaminated
hands.
-
Food-borne outbreaks of streptococcal disease can occur.
- Kissing and transfer of infected saliva in infectious
mononucleosis
- Oral sex with
Neisseria
gonorrhoeae infection
Pathogenesis of infection
- Viral infections
- With respiratory virus infections, such as adenovinis and coxsackie
virus, there is evidence that direct invasion of pharyngeal mucosa occurs.
- The
usual pathologic changes occurring in viral pharyngitis are edema and hyperemia
of the tonsils and the pharyngeal mucous membrane.
- An inflammatory exudate may
be present with adenovirus and EBV virus infections; with the latter,
nasopharyngeal lymphoid hyperplasia also occurs.
- Streptococcal infection
- The events leading to invasive streptococcal infection of the pharymx and
tonsil are also not well understood.
- Pharyngeal carriage of S. pyogenes is commonly
observed in asymptomatic people.
- Factors that influence the balance between
colonization and invasive infection may include natural and acquired host
immunity and interference among the bacteria present in the oropharynx.
- Streptococcus
pyogenes elaborates a number of extracellular factors, including
erythrogenic toxin, hemolysins, streptokinase, deoxyribonuclease, proteinase,
and hyaluronidase, which are of known or possible pathogenic importance. Certain
M serotypes (1,2,4, and 12) of streptococci have been most frequently isolated
from patients with uncomplicated pharyngitis, and others (1,3, and 12) from
patients with serious invasive infection.
- Scarlet fever results from infection with a streptococcal strain that
elaborates streptococcal pyrogenic exotoxin (erythrogenic toxin). Toxin
production is dependent on lysogeny of the infecting streptococcus by a
temperate bacteriophage.
Establishment of specific diagnosis
The primary objectives in the diagnosis of acute pharyngitis, are to
distinguish cases of common viral etiology from those due to S. pyogenes and
to detect and identify the occasional case due to an unusual or rare cause for
which treatment is available in the majority of cases, but where an etiologic
diagnosis is not possible on clinical grounds alone.
- Streptococcal
pharyngitis.
- Throat culture (48 hours) is the preferred method for diagnosing streptococcal
pharyngitis.
- Rapid streptococcal antigen screen
(45 minutes) is highly specific but the sensitivity is
approximately 85%.
- Serum antibody titers do not rise until convalescence and are thus of no help
in short-term management.
- Infectious mononucleosis.
- Heterophile antibody test (monospot test) is used to diagnose suspected
infectious mononucleosis.
- Diphtheria
-
Neisseria
gonorrhoeae
Long-term consequences of streptococcal pharyngitis
-
Rheumatic fever
- occurs in about 3% of times following Streptococcal
pharyngitis.
- is a non-suppurative sequela of Streptococcus
pyogenes infections.
- It occurs approximately 3 weeks after streptococcal
pharyngitis
- M protein has been found to be antiphagocytic and it
also has epitopes which are antigenically similar to one found in the
cardiac myosin and sarcolemmal membrane proteins.
- Acute RF is thought to be an auto-immune disease.
- Antibodies directed against M protein cross-react with
cardiac tissue.
- These antibodies bind to the cross-reactive antigens in
muscle and damage the muscle tissue. Other group A strep antigens may
also cross-react with other cardiac antigens causing damage to the heart
valves.
- Acute glomerulonephritis
are late complications
of streptococcal infection and are related to immunologic response to group A
streptococcal, infection.
Strategy for pharyngitis therapy
Since even exudative tonsillitis is usually of viral origin, for
which there is no specific therapy, the use of antibiotics should be guided by
the results of antigen detection tests or cultures, unless there are strong
clinical and epidemiologic grounds to suspect a streptococcal infection.
Therapy of Streptococcal pharyngitis
- Oral penicillins, cephalosporins, erythromycin and clindamycin are effective
against Group A streptococcus.
- Sulfonamides are ineffective against group A streptococcal pharyngitis.
- Streptococcal pharyngitis is best treated orally with penicillin (125-250 mg
of penicillin V three times daily for 10 days).
- This usually produces prompt
clinical response with defervescence within 24 hr. and shortens the course of
illness by an average of 1.3 days.
- Administration of a single intramuscular injection of 600,000 - 1.2 million
units of benzathine penicillin G is a satisfactory alternative.
- A streptococcal carrier is not at risk for rheumatic fever, is unlikely to
transmit infection, and does not require treatment unless there is a history of
rheumatic fever in the patient or a sibling.
- A few children require antibiotic
prophylaxis against streptococcal. disease, such as those with past history of
rheumatic fever.
- In penicillin allergic patients, erythromycin is the therapy of choice.
- Symtomatic therapy (Tylenol, Fluids and electrolytes)
- Complications ( Acute glomerulonephritis, Carditis etc)
Rationale for therapy of streptococcal pharyngitis
- Decrease duration of symptoms
- The primary rationale for detection and treatment of streptococcal pharyngitis
is to prevent the subsequent development of rheumatic fever. Treatment of group A streptococcal pharyngitis as long as 9 days after
onset is still effective in the prevention of rheumatic fever.
- There is no convincing evidence that treatment affects the incidence
or severity of acute glomerulonephritis.