Airborne Bacterial Diseases

1. Chapter 10 Airborne Bacterial Diseases

2. 10.1 Structure and Indigenous Microbiota of the Respiratory System Upper respiratory defenses limit microbe colonization of the lower respiratory tract. Microbial colonization is usually limited to the upper respiratory tract. Mucociliary clearance traps microbes and particulates larger than 2 �m in a layer of mucus.

3. FIGURE 4: Staphylococcus in the Ciliated Epithelium

4. 10.2 Bacterial Diseases Affecting the Upper Respiratory Tract Pharyngitis is an inflammation of the throat. S. pyogenes causes streptococcal pharyngitis (strep throat). It enters the upper respiratory tract through respiratory droplets. Some patients with strep throat may develop scarlet fever, exhibiting a rash caused by erythrogenic exotoxins.

5. Strep throat and scarlet fever can be treated by antibiotics. Rheumatic fever is a serious complication affecting the joints and heart. It causes permanent heart damage called rheumatic heart disease. Acute glomerulonephritus is a rare inflammatory response to M proteins. It may lead to renal damage.

6. Diphtheria is a life-threatening illness. Diphtheria is a local infection of the throat caused by Corynebacterium diphtheriae. C. diphtheriae bacilli remain in clumps after multiplying, forming a palisade layer. Diphtheria is acquired by respiratory droplet transmission. The bacteria produce an exotoxin that inhibits translation. This results in the accumulation of a pseudomembrane on the tonsils or pharynx.

7. Treatment requires antibiotics and antitoxins. Injection of diphtheria toxoid is used for vaccination. There are usually less than a dozen confirmed cases in the United States each year.

8. The nose is the most commonly infected part of the upper respiratory tract. Ear infections are common illnesses in early childhood.

9. Acute bacterial meningitis is a rapidly developing inflammation. Bacterial meningitis begins when a localized infection invades the blood and then the meninges around the brain and spinal cord.

10. Neisseria meningitidis causes meningococcal meningitis. Neisseria meningitidis is the major cause of disease and mortality in infants. 90% of the cases occur in Africa�s meningitis belt.

11. Other causes of meningitis Streptococcus pneumoniae causes pneumococcal meningitis, about 30% of the cases of meningitis. Haemophilus influenzae Type b (Hib) is mostly prevented now in the US with the Hib vaccine.

12. Pertussis (Whooping Cough) is highly contagious. Bordatella pertussis is spread by respiratory droplet transmission. Toxin paralyzes ciliated cells in the respiratory tract. 10.3 Bacterial Diseases of the Lower Respiratory Tract

13. Patients experience multiple paroxysms of coughs, followed by an inhalation of breath that sounds like a �whoop.� Erythromycin reduces the duration and severity of illness. The newer vaccine (DTaP) contains B. pertussis chemical extracts rather than killed cells. The number of cases in the United States has been rising since 1981.

14. Tuberculosis Is One of the Greatest Challenges to Global Health. 2 million people die of TB every year, globally. Mycobacterium tuberculosis enters the respiratory tract in small aerosolized droplets. About 90% of people who carry latent tuberculosis will never develop an active infection. They may never even know they are infected. Clinical TB develops within 3 months and can be transmitted to others.

15. Sputum coughed from the lower respiratory tract may contain blood. Macrophages accumulate in the lung. They form a tubercle that harbors M. tuberculosis. If a tubercle breaks apart, bacteria spread throughout the body.

16. Miliary tuberculosis is the development of active tubercles throughout the body. The tuberculin reaction in the Mantoux test can be used for early detection of TB exposure.

17. Multidrug-resistance Mycobacterium tuberculosis is affecting which antibiotics are used to treat TB. TB is a particularly big problem for AIDS patients. Attenuated M. bovis is used in BCG immunization.

18. Infectious bronchitis is an inflammation of the bronchi. Bronchitis produces excessive mucus and a narrowing of the bronchi.

19. �Typical� Pneumonia Can Be Caused by Several Bacteria. 80% of �typical� pneumonia cases are caused by Streptococcus pneumoniae. It is acquired through aerosolized droplets or contact. Pneumococcal pneumonia can involve: an entire lung lobe (lobar pneumonia). both lungs (double pneumonia). or patches in the respiratory passageways (bronchopneumonia).

20. Haemophilus influenzae can cause: �typical� pneumonia. otitis media sinusitis. Staphylococcus aureus is a common hospital-acquired form of pneumonia. It may result in necrotizing pneumonia. Klebsiella pneumoniae can be a primary or secondary infection in people with impaired pulmonary function.

21. �Atypical� Pneumonia Can Be Caused by a Diverse Group of Bacterial Species. Mycoplasma pneumoniae causes primary atypical pneumonia, often called walking pneumonia. M. pneumoniae has no sensitivity to penicillin because it has no cell wall. The cold agglutinin screening test (CAST) is used to assist diagnosis.

22. Legionella pneumophila causes Legionnaires� disease. It lives where water collects and becomes airborne in the wind (or ventilation system). Disease develops within a week of inhalation of contaminated droplets. Necrotizing pneumonia may develop. L. pneumophila also causes Pontiac fever, an influenza-like infection.

23. Other Pneumonia-Causing Bacterial Species are Obligate, Intracellular Parasites. Coxiella burnetii causes Q fever, a prevalent disease of livestock. Humans can acquire the disease by consuming contaminated raw or improperly pasteurized milk.

24. Chlamydia psittaci causes psittacosis (a.k.a. ornithosis). It is a zoonotic disease humans can catch from infected birds. Chlamydia pneumoniae causes chlamydial pneumonia.