Lower respiratory tract

1. Lower respiratory tract • Lungs are axenic (no normal flora) • Pneumonia • Described by location, pathogen or way contracted • Pleurisy

2. Pneumococcal Pneumonia • Most common bacterial pneumonia • Causative agent • Streptococcus pnuemoniae • Gram positive • Encapsulated, diplococci

3. Signs and Symptoms • Cough; fever; congestion; chest pain; rust tinged sputum • Breathing becomes shallow and rapid • Skin becomes dusky due to poor oxygenation • Consolidation may occur

4. Recovery is usually complete • Most strains do not cause permanent damage to lung tissue • Complications • Pleural effusions • Septicemia • Endocarditis • Meningitis

5. Epidemiology • 75% of healthy individuals carry encapsulated strain in their throat • Bacterial rarely reach lung • Risk of pneumonia rises when cilia destroyed • Gram stain of sputum used for diagnosis • Pneumococci confirmed with quelling reaction

6. Bacteria that reach alveoli cause inflammatory response • Adhesions • Capsule • Phosphorylocholine in cell wall • Pneumolysin (cytotoxin) • IGA proteases

7. Prevention • Pneumococcal vaccine • Treatment • Antibiotics successful if given early • Penicillin (some resistance) • Erythromycin, cephalosporin and chloramphenicol

8. Klebsiella Pneumonia • Leading cause of nosocomial pneumonia • Causative agent • Klebsiella pneumoniae • Gram negative • Encapsulated, Bacillus • Produce mucoid colonies

9. Signs and Symptoms: • Typical pneumonia symptoms combined with a thick, bloody sputum and recurrent chills • Organism causes tissue death • Leads to formation abscess in lung or other tissues • Endotoxin can trigger shock and disseminated intravascular coagulation

10. Epidemiology • Endogenous • Difficult for K. pneumoniae to infect lungs of healthy persons • Leading causes of nosocomial death • Also causes UTI, meningitis and wound infections • Diagnosed with chest x-ray and sputum culture

11. Prevention • No vaccine available • Employ good aseptic technique • Treatment • Antimicrobial treatment limited • Cephalosporin combined with an aminoglycoside • Tissue damage and release of endotoxin can cause permanent damage to lungs • High fatalities even with treatment

12. Mycoplasmal Pneumonia • “Walking pneumonia” • Leading pneumonia in children • Causative agent • Mycoplasma pneumoniae • Small, pleomorphic, Gram + • No cell wall • Prominent capsule

13. Signs and Symptoms • Onset is gradual • 1-4 week incubation period • First symptoms include • Fever, headache, muscle pain, fatigue, sore throat and excessive sweating • atypical for pneumonia • Persistent dry cough for several weeks

14. Organism attaches to receptors on epithelium • Adhesion protein • Interferes with cilia, cells die and slough off • Capsule protects it from phagocytosis • Inflammation initiates thickening of bronchial and alveolar walls • Causes difficulty in breathing

15. Epidemiology • Spread through aerosol droplets • Survive for long periods in secretions • Grow slowly in culture • 2-6 weeks for “fried egg” colonies to appear • Diagnosis difficult • Serological tests required

16. Prevention and treatment • No practical prevention • Avoid crowding in schools and military facilities • Aseptic technique • Antibiotic treatment • Penicillins are ineffectual (WHY?) • Antibiotics of choice are tetracycline and erythromycin

17. Pertussis • Whooping Cough • Causative agent • Bordetella pertussis • Small, Gram negative • Encapsulated, coccobacillus

18. Signs and Symptoms: • Catarrhal stage – cold symptoms (1-2 weeks) • Paroxysmal stage – severe coughing (2-4 weeks) • Coughing followed by characteristic “whoop” • May cause vessels in eyes to rupture • Cyanosis • Vomiting, diarrhea and seizure may occur • Convalescent phase –persistent cough (months)

19. Pathogen enters respiratory tract and attaches to ciliated cells • Produces 2 forms of adhesions • Colonizes upper and lower respiratory tract • Produces numerous toxic products • Mucus secretion increases and cilia action decreases • Cough reflex is only mechanism for clearing secretions • Decreased blood flow and WBC activity

20. Epidemiology • Spreads via infected respiratory droplets • Highly contagious • Most infectious during runny nose period • Classically disease of infants • Often overlooked as a persistent cold in adults • High risk of secondary infections!

21. Prevention Immunization Combined with Diphtheria and tetanus toxoids DTaP Treatment Primarily supportive Erythromycin may reduce infectivity if given early

22. Tuberculosis • TB; Consumption • Causative agent • Mycobacterium tuberculosis • Gram positive • Acid fast, slender bacillus • Cord factor

23. Signs and Symptoms • Chronic illness • Initial symptoms: • Minor cough and mild fever • Progressive symptoms: • Fatigue; night sweats; weight loss; chest pain and labored breathing • Chronic productive cough • Sputum often bloody

24. 3 types of tuberculosis: • Primary TB- initial case of tuberculosis disease • Secondary TB - reactivated • Disseminated TB- tuberculosis involving multiple systems

25. Primary TB • Transmitted through respiratory droplets • Pathogens taken up by alveolar macrophages • fusion of phagosome with lysosomes prevented • Pathogen replicates inside macrophages slowly killing them • Intense immune reaction occurs • WBCs surround infected cells and release inflammatory chemicals

26. Other body cells deposit collagen fibers • macrophages and lung cells form tubercle • Infected cells die producing caseous (cheesy) necrosis • Body may deposit calcium around tubercles • Ghon complex

27. Secondary TB • tubercle ruptures and reestablishes active infection • More common in immunosupressed • Leading killer of HIV+ individuals • Disseminated TB • Some macrophages carry pathogen through blood and lymph to other sites of body • Bone marrow, spleen, kidneys, spinal cord and brain

29. Epidemiology • 1/3 of world population infected • Annual mortality of ~ 2 million • Estimated 10 million Americans infected • Rate highest among non-white, elderly poor people • Small infecting dose • As little as ten inhaled organisms • Not very virulent but high mortality

30. Tuberculin test • Tuberculosis antigen injected under skin • Injection site become red and firm if positive • Positive test does not indicate active disease • Definitive tests include sputum samples and chest x-rays

31. Prevention Vaccination used in other parts of the world Prophylactic antibacterial treatment for exposed individuals Treatment Antibiotic treatment Rifampin, Isoniazid, streptomycin and ethambutol MDR strains Therapy lasts up to 6 months (DOTS)