Pneumonias and Fungal infections

1. Pneumonias and Fungal infections Dr.FARHANA ZAKARIA

2. PNUEMONIA • Defined as acute infection of the lung parenchyma distal to the terminal bronchioles

3. Pathogenesis • Microorganisms gain entry into the lungs by one of the following routes : • Inhalation of microbes present in air • Aspiration of organisms from the nasopharynx or oropharynx • Hematogenous spread from a distant focus of infection • Direct spread from an adjoining site of infection.

4. Etiologic classification of pneumonias • BACTERIAL PNEUMONIA • Lobar pneumonia • Bronchopneumonia • VIRAL AND MYCOPLASMAL PNEUMONIA • OTHER TYPES OF PNEUMONIAS • Pneumocystiscarini pneumonia • Legionella pneumonia • Aspiration pneumonia

5. Anatomical classification • Lobar pneumonia • Broncho pneumonia • Interstitial pneumonia

6. Bacterial pneumonia • Most common cause of pneumonia

7. Lobar pneumonia • Is an acute bacterial infection of a part of a lobe , the entire lobe or even two lobes of one or both the lungs • Lower lobes are affected most commonly • Etiology • Pneumococcal pneumonia – more than 90% of all lobar pneumonias are caused by streptococcus pneumoniae . • Is community acquired infection

8. Staphylococcal pneumonia – staphylococcus aureus causes pneumonia by hematogenous spread of infection. • Streptococcal pneumonia – β-hemolytic streptococci cause pneumonia in severely debilitated elderly patients and in diabetics • Pneumonia by gram-negative aerobic bacteria • Like haemophilus influenza , klebsiella pneumonia, pseudomonas, proteus , E coli , H.influenza.

9. Morphologic features • Lobar pneumonia can be divided into 4 sequential pathologic phases: • Stage of congestion • Red hepatisation • Grey hepatisation • Resolution

10. Stage of congestion – initial phase • Represents early acute inflammatory response to bacterial infection and lasts for 1 to 2 days. • Grossly – affected lobe is enlarged , heavy , dark red and congested . • C/S exudes blood-stained frothy fluid

11. Histologically : • Dilatation and congestion of capillaries in the alveolar walls. • Pale eosinophilic edema fluid in the air spaces • Few red cells and neutrophils in the intra-alveolar fluid. • Numerous bacteria demonstrated in the alveolar fluid by gram’s staining.

12. Red hepatisation – early consolidation • Lasts for 2 to 4 days • Liver-like consistency of afected lobe on C/S • Grossly: • Affected lobe is red , firm and consolidated • C/S of involved lobe is airless , red-pink , dry , granular and has liver-like consistency • Accompanied by serofibrinous pleurisy.

13. Histologically , • Edema fluid of preceding stage is replaced by strands of fibrin • Marked cellular exudate of neutrophils and extravasation of red cells • Many neutrophils show ingested bacteria • The alveolar septa are less prominent than in the first stage due to cellular exudation.

14. Grey hepatisation – late consolidation • This phase lasts for 4 to 8 days • Grossly , the affected lobe is firm and heavy. • C/S is dry, granular and grey in appearance with liver-like consistency . • Change in color from red to grey begins at hilum and spreads towards the periphery . • Fibrinous pleurisy is prominent.

15. Histologically, • Fibrin strands are dense and more numerous • Cellular exudate of neutrophils is reduced due to disintegration of many inflammatory cells. Red cells are also fewer. • Macrophages begin to appear in the exudate • Cellular exudate is often separated from the septal walls by a thin clear space. • Organisms are less numerous and appear as degenerated forms.

16. Resolution • This stage begins by 8th to 9th day if no chemotherapy is administered and completed in 1 to 3 weeks. • Grossly , • Previously solid fibrinous constituent is liquefied by enzymatic action , eventually restoring normal aeration in the affected lobe.

17. Process of softening begins centrally and spreads to periphery. • C/S is grey- red or dirty brown and frothy , yellow , creamy fluid can be expressed on pressing. • Pleural reaction may also show reaction but may undergo organisation leading to fibrous obliteration of pleural cavity.

18. Histologically , • Macrophages are predominant cells in the alveolar spaces , neutrophils diminish in number. • Granular and fragmented strands of fibrin in the alveolar spaces are seen • Alveolar capillaries are engorged • There is progressive removal of fluid content as well as cellular exudate from the air spaces.

19. Complications • Organisation • Pleural effusion • Empyema • Lung abscess • Metastatic infection

20. Bronchopneumonia • Infection of terminal bronchioles that extends into surrounding alveoli resulting in patchy consolidation of lung. • Frequent at extremes of life , as a terminal event in chronic debilitating diseases and as a secondary infection following viral respiratory infections • Common organisms- staphylococci , streptococci , pneumococci , klebsiella pneumonia, haemophilus influenza , pseudomonas.

21. Gross • Patchy areas of red or grey consolidation affecting one or more lobes , frequently found bilaterally and more often involving lower zones of the lungs . • C/S – dry , granular , firm , red or grey in color , 3 to 4 cms in diameter , slightly elevated over the surface and are often centered around a bronchiole.

22. Histologically • Acute bronchiolitis • Suppurativeexudate in the peribronchiolar alveoli • Thickening of the alveolar septa by congested capillaries and leucocytic infiltration • Less involved alveoli contain edema fluid.

24. Fungal infections of lung • More common than tuberculosis in US. • These infections in healthy individuals are rarely serious but in immunosuppressed individuals may prove fatal

25. Histoplasmosis • Caused by histoplasmacapsulatum • By inhalation of infected dust or bird droppings. • May remain asymptomatic or may produce lesions similar to ghon’s complex.

26. Coccidioidomycosis • Caused by coccidioidesimmitis , spherical spores • Infection is acquired by close contact with infected dogs. • Lesions consist of peripheral parenchymalgranuloma in the lung

27. Cryptococcosis • Caused by cryptococcusneoformans which is round yeast having a halo around it due to shrinkage in tissue sections. • Infections occurs by inhalation of pigeon droppings. • Lesions range from small parenchymalgranuloma in the lung to cryptococcal meningitis.

28. Blastomycosis • Caused by blastomycesdermatitidis. • Result from inhalation of spores in the ground. • May present as ghon’s complex-like lesion , as a pneumonic consolidation , and as multiple skin nodules.

29. Aspergillosis • Most common fungal infection of the lung caused by aspergillusfumigatus. • Fungus exists as a thin septatehyphae with dichotomous branching and grows best in cool , wet climate. • Result in allergic bronchopulmonaryaspergillosis , aspergilloma and necrotising bronchitis.

30. Immunocompromised persons develop more serious manifestations of aspergillus infection.

31. Mucormycosis • Caused by Mucor and Rhizopus. • Pulmonary lesions are especially common in patients with diabetic ketoacidosis.

32. Candidiasis • Caused by candidaalbicans.- normal commensal in oral cavity, gut and vagina. • Attains pathological forms in immunocompromised host. • Angio-invasive growth of the organism occurs in the airways.