I. AIRBORNE BACTERIAL DISEASES

1. Diseases of the Upper Respiratory Tract

A. Streptococcal DiseasesStreptococci are a large and diverse group of encapsulated, nonmotile, facultatively anaerobic, gram-positive cocci.

a. Streptococcal pharyngitis

i. Causative agent: S. Pyogenes: cells reach the upper respiratory tract within respiratory droplets expelled by infected persons during coughing and sneezing.ii. Clinical Manifestations:1. Sore Throat2. fever,3. headache, 4. swollen lymph nodes and tonsils,5. beefy red appearance to pharyngeal tissuesb. Scarlet feveri. Causative agent: S. Pyogenes: cells carry toxin-encoding prophagesii. Clinical Manifestations:1. pink-red skin rash on the neck, chest, and soft-skin areas of the arms.2. sore throat, fever, and1. swollen neck glandsB. Diphtheriai. Causative agent: Corynebacterium diphtheriae: acquired by inhaling respiratory droplets from an infected person.ii. Clinical Manifestations:1. Sore throat2. Low-grade feveriii. Treatment:1. Treatment requires antibiotics (penicillin or erythromycin) to eradicate the pathogen and 2. Antitoxins to neutralize the exotoxins.

C. Pertussis: droplets that adhere toand aggregate on the cilia of epithelial cells of the respiratory tracti. Causative agent: Bordetella pertussis,: the bacilli are spread by respiratory ii. Clinical Manifestations:1. Initial Stage: a. General malaiseb. Low-grade feverc. Increasingly sever cough2. Next Phasea. Labored breathing, experience multiple paroxysms, which consist of rapid-fire staccato coughs all in one exhalation, followed by a forced inhalation over partially closed glottis. The rapid inhalation results in the characteristic "whoop" (hence, the name whooping cough).

iii. Treatment:1. Eradication of the bacterial cells is generally successful when erythromycin is administered before the respiratory passageways become blocked. However, antibiotic treatment only reduces the duration and severity of the illness.D. Bacterial Meningitis

a. Neisseria meningitidis. The pathogen is a small, nonmotile, encapsulated, aerobic, gram-negative diplococcus that attaches to the nasopharyngeal mucosa by pili.

i. Waterhouse-Friderichsen Syndrome

b. Streptococcus pneumoniae. Referred to as the pneumococci, S. pneumoniae has the same cell characteristics as S. pyogenes. The pneumococcus is not only responsible for many cases of pneumonia but also is the agent responsible for about 30 percent of meningitis cases.

c. Haemophilus influenzae type b (Hib) once was the most prevalent bacterial species causing meningitis (Haemophilus meningitis) in children between the ages of two months and five years.

All three bacterial species discussed above enter the body by respiratory droplets from prolonged contact, such as coughing, sneezing, or kissing. They then colonize the nasopharynx and sinus cavities.

In the case of N. meningitidis, the disease consists of an influenza-like upper respiratory infection called meningococcal pharyngitis.

However, should the organism invade into the nonciliated epithelium and spread to the blood, a condition called meningococcemia occurs and the bacterial cells multiply rapidly.

Once in the blood, all three pathogens are capable of crossing the blood-brain barrier.

The meninges then become inflamed, causing pressure on the spinal cord and brain.

Clinical Manifestations: Patients normally experience a fever and stiff, neck; symptoms a pounding headache, nausea vomiting, and often sensitivity to bright light.