Diseases Of The Respiratory System

Microbial Diseases of the Upper Respiratory System

Specific areas of the upper respiratory system can become infected to produce pharyngitis, laryngitis, tonsillitis, sinusitis, and epiglottis.

These infections may be caused by several bacteria and viruses, often in combination.

Most respiratory tract infections are self-limiting.

H. influenzae type b can cause epiglottitis.

Bacterial Diseases of the Upper Respiratory System

Streptococcal Pharyngitis (Strep Throat)

Caused by S. pyogenes (group A beta-hemolytic streptococcus). S. pyogenes is resistant to phagocytosis and produces streptokinase, DNAse and hemolysins.

Symptoms are inflammation of the mucous membrane and fever; tonsillitis and otitis media may also occur.

Preliminary rapid diagnosis by indirect agglutination tests. Definitive diagnosis is based on a rise in IgM antibodies.

Penicillin is used to treat streptococcal pharyngitis.

Immunity does not usually develop (it is type-specific).

Transmitted by respiratory route but at one time was associated with unpasteurized milk.

Streptococcal Pharyngitis

Scarlet Fever

Strep throat caused by erythrogenic toxin producing strains of Streptococcus pyogenes results in scarlet fever.

Erythrogenic toxin production is caused by a phage.

Symptoms include a red rash, high fever, red enlarged tongue.

Penicillin is the drug of choice.

Immunity is developed to the toxin not the organism.

Scarlet Fever Rash


Diphtheria is caused by an exotoxin-producing gram-positive rod, Corynebacterium diphtheriae.

Corynebacterium diphtheriae

A potent exotoxin is produced when the bacteria are lysogenized by a phage.

Pseudomembrane formation occurs in the throat. The membrane contains fibrin and dead human and bacterial cells and can block the passage of air.

Diphtheria Membrane

The exotoxin inhibits protein synthesis and may damage the heart, kidney and/or nerves.

Laboratory diagnosis is based on isolation and identification.

Treatment: Administer antitoxin to neutralize the toxin and antibiotics to stop growth of the bacteria.

Prevention: Immunization with DPT.

Cutaneous diphtheria is characterized by slow healing skin ulcerations.

There is minimal dissemination of exotoxin in the bloodstream.

Otitis Media

Often a complication of nose and throat infections but can also be caused by direct inoculation.

Pus accumulation causes pressure on the tympanic membrane.

Common bacterial causes:

Acute Otitis Media with Bulging Eardrum