http://microbiology2009.wikispaces.com/
Research paper
What is pharyngitis: an upper respiratory tract infection.
Pharyngitis is the inflammation of the pharynx. The pharynx is the part of the neck and throat
situated immediately posterior to (behind) the mouth and nasal cavity.
Causes of pharyngitis: Viruses and bacteria most common
Bacterial Causes:
---Streptococcus pyogene – The most significant bacterial agent causing pharyngitis in both
adults and children is Streptococcus pyogenes. Streptococcus pyogenes is a Gram-positive
facultative anaerobic bacterium. It is not motile, and does not produce spores. It occurs as long
chains of cocci, and occasionally in pairs. S pyogenes tends to colonize the upper respiratory
tract and is highly potent as it overcomes the host defense system. The cell wall of S pyogenes is
very complex and chemically diverse. The antigenic components of the cell are the virulence
factors. The extracellular components responsible for the disease process include invasins and
exotoxins. The outermost capsule is composed of hyaluronic acid, which has a chemical
structure resembling host connective tissue, allowing the bacterium to escape recognition by the
host as an offending agent. Thus, the bacterium escapes phagocytosis by neutrophils or
macrophages, allowing it to colonize.
Other bacterial causes:
----Arcanobacterium haemolyticus
-----M pneumonia
------C pneumonia
-----Neisseria gonorrhoeae- Very rarely does it cause pharyngitis but there have been some cases
in which it has done so. The reason I mention this is because it is one of the aerobic, gram
negative bacteria we learned in chapter 11.
Viral Causes: Most common viruses that cause pharyngitis are rhinovirus and coronavirus.
Rhinovirus: Rhinoviruses are positive strand RNA viruses with a naked nucleocapsid. They are
sensitive to low pH and are spread by aerosols and infect the upper respiratory track. Rhinoviruses
are quite stable, lasting for hours on fomites, but are sensitive to temperature. Since they are sensitive to
temperature they do not spread to the lower respiratory tract because they replicate best at a few degrees
below normal body temperature.
Coronavirus: were first isolated from chickens in 1937. They are the largest positive strand RNA
viruses. They infect humans and animals in which they cause respiratory infections such as
pharyngitis. Most people harbor anti-coronavirus antibodies but reinfection is common
indicating that there are many circulating serotypes of the virus in the human population. Most
coronavirus infections go undiagnosed and the disease is self-limiting. Diagnosis can be carried
out using immuno-electron microscopy and serology. There are no anti-virals for routine
coronavirus infections but over-the-counter remedies to alleviate symptoms are useful.