INFECTIOUS DISEASES�AETIOLOGY PATHOGENESIS &�CONSEQUENCES �

INFECTIOUS DISEASES�AETIOLOGY PATHOGENESIS &�CONSEQUENCES �by Dr.T.V.Rao MD

1. INFECTIOUS DISEASES AETIOLOGY PATHOGENESIS & CONSEQUENCES Dr.T.V.Rao MD

2. in·fec·tion dictionary means a. Invasion by and multiplication of pathogenic microorganisms in a bodily part or tissue, which may produce subsequent tissue injury and progress to overt disease through a variety of cellular or toxic mechanisms. b . The pathological state resulting from having been infected. Dr.T.V.Rao MD 2

3. Definitions Disease and Infectious Disease Disease Any deviation from a condition of good health and well-being Infectious Disease A disease condition caused by the presence or growth of infectious microorganisms or parasites Dr.T.V.Rao MD 3

4. Definitions Pathogenicity and Virulence Pathogenicity The ability of a microbe to cause disease This term is often used to describe or compare species Virulence The degree of pathogenicity in a microorganism This term is often used to describe or compare strains within a species Dr.T.V.Rao MD 4

5. Principles of Infection Understanding the basic principles of infection is essential for any health care worker in any field of health care. Disease transmission Prevention of disease transmission

6. Nature of Microorganisms Microorganisms (microbes) are small, living organisms that are not visible to the naked eye. Pathogens (germs) are microorganisms that cause disease. Non-pathogens are microorganisms that do not cause disease; can be beneficial.

7. Infection is the invasion of a host organism's bodily tissues by disease-causing organisms, their multiplication, and the reaction of host tissues to these organisms and the toxins they produce. Infections are caused by microorganisms such as viruses, prions, bacteria, and Viroids, and larger organisms like parasites and fungi. Infection means Dr.T.V.Rao MD 7

8. What is an Infection? A harmful invasion and spread of foreign species, or pathogen, in a host. VIRUS Small pox, measles, influenza, Ebola PRIONS Cow’s disease BACTERIA Tuberculosis, pneumonia, salmonella, anthrax FUNGUS Athlete’s foot, ring worm PROTISTS Malaria, toxoplasmosis, Algae

9. COURSE OF INFECTIOUS DISEASEs Exposure/Invasion of Host Incubation -- period of time between exposure and onset of symptoms -- e.g., interval between HIV infection and development of AIDS can be as long as 10-15 years Host reaction Dr.T.V.Rao MD 9

10. Nature of Microorganisms Saprophytes Parasites Pathogens

11. Causative Agents effecting humans Bacteria Viruses Fungi Protozoa Helminths Prions Dr.T.V.Rao MD 11

12. Streptococci (chains) Staphylococci (clusters) Diplococci (pairs) Micrococci (tiny) Flagellated forms (tails) Bacilli (rod-shaped) Vibrios Spirilla (spiral) Spirochetes (comma) Types of Bacteria

13. Fungi A plantlike organism that lives on dead organic matter. Yeasts and molds can be pathogenic. Cause conditions such as ringworm, athlete’s foot, yeast infections, and thrush. Antibiotics do not kill fungi. Antifungal medications are available, but expensive and may cause liver damage. Types of Microorganisms

14. Types of Microorganisms Protozoa One-celled animal like organisms often found in decayed materials and contaminated water. Many contain flagella which allow them to move freely. Cause diseases such as malaria, trichomonas, and amebic dysentery.

15. Viruses Smallest of all microorganisms – visible only using an electron microscope. Cannot reproduce unless they are inside another living cell. Spread by contact with blood and other body fluids. Difficult to destroy. Not affected by antibiotics. Associated with diseases such as the common cold, chicken pox, herpes, hepatitis B, measles, warts, polio, influenza, and AIDS. Types of Microorganism s

16. Classification of Infections Primary Infection Reinfection Secondary Infection, Focal infection, Cross infection, Nosocomial infections Iatrogenic infection

17. Source of Infections Endogenous infection Exogenous infections

18. Clinical Presentations In apparent infection subclinical Infection In apparent infection, Atypical infections Latent infections

19. Source of Infection Humans from patient or carrier A healthy carrier Convalescent carrier Temporary carrier Contact carrier Paradoxical carrier

20. Source of Infections Animals Insects vectors Mechanical vector Biological vector Soil and water Food

21. MODES OF COMMUNICABLE DISEASE TRANSMISSION Direct Transmission Indirect Transmission Dr.T.V.Rao MD 21

22. Modes of Transmission Direct contact Indirect contact Droplet transmission Hands Vector-borne Nosocom ial Dr.T.V.Rao MD 22

23. Transmission of Pathogens Direct contact Indirect contacts Air Objects Vectors

24. Modes of Transmission Direct transmission Indirect transmission Direct contact Airborne Droplet spread Vehicle borne Vector borne

25. DIRECT TRANSMISSION Immediate transfer of the disease agent by direct contact between the infected and the susceptible individuals Occurs through such acts as touching, biting, kissing, sexual intercourse, or by direct projection (droplet spread) by coughing or sneezing within a distance of one meter Examples of diseases for which transmission is usually direct are AIDS, syphilis, gonorrhea, and the common cold Dr.T.V.Rao MD 25

26. INDIRECT TRANSMISSION May be one of three types: air-borne, vehicle-borne, or vector-borne Air-borne transmission -- transmission of microbial aerosols to a suitable port of entry, usually the respiratory tract Microbial aerosols are suspensions of dust or droplet nuclei made up wholly or in part by microorganisms -- may be suspended and infective for long periods of time Examples of air-borne diseases include tuberculosis, influenza, Histoplasmosis, and Legionellosis Dr.T.V.Rao MD 26

27. INDIRECT TRANSMISSION (cont’d.) Vehicle-borne transmission -- contaminated materials or objects (fomites) serve as vehicles , nonliving objects by which communicable agents are transferred to a susceptible host The agent may or may not have multiplied or developed on the vehicle Examples of vehicles include toys, handkerchiefs, soiled clothes, bedding, food service utensils, and surgical instruments Dr.T.V.Rao MD 27

28. INDIRECT TRANSMISSION (cont’d.) Also considered vehicles are water, milk, food (e.g., common vehicles), or biological products such as blood, serum, plasma, organs and tissues Almost any disease can be transmitted by vehicles, including those for which the primary mode of transmission is direct, such as dysentery and hepatitis

29. Causing an Infection Endogenous – disease originates within the body. Ex: metabolic disorders, congenital abnormalities, tumors. Exogenous – disease originates outside the body. Ex: chemical agents, electrical shock, trauma. Nosocomial – acquired by an individual in a health care facility (workers to patient). Many are antibiotic resistant, life-threatening. Opportunistic – occur when the body’s defenses are weak. Ex: pneumonia w/AIDs.

30. Signs & Symptoms of Infection Redness Swelling Tenderness Warmth Drainage Red streaks leading away from wound Dr.T.V.Rao MD 30

31. Development of Infection: Clinical Signs and Symptoms Local signs Inflammation Purulent exudate if bacterial infection; serous exudate if viral Tissue necrosis Lymphadenopathy Respiratory effects Systemic signs Fever, fatigue, headache, nausea Dr.T.V.Rao MD 31

32. Generalized Stages of Infection 1. Entry of Pathogen Portal of Entry 2. Colonization Usually at the site of entry 3. Incubation Period Asymptomatic period Between the initial contact with the microbe and the appearance of the first symptoms Dr.T.V.Rao MD 32

33. Generalized Stages of Infection 4. Prodromal Symptoms Initial Symptoms 5. Invasive period Increasing Severity of Symptoms Fever Inflammation and Swelling Tissue Damage Infection May Spread to Other Sites Acme (Fastigium) Dr.T.V.Rao MD 33

34. Factors predisposing pathogenicity Pathogenicity means ability of the microbe to produce disease or tissue injury Virulence M ay undergo variation

35. Virulence and Pathogenicity Pathogenicity: capacity of microbes to cause disease Virulence: degree of pathogenicity of specific microbe Based on: Invasive qualities Toxic qualities Presence of pili or fimbriae for adhesion Ability to avoid host defenses (mutate) Dr.T.V.Rao MD 35

36. Virulence Factors and Toxins State of the Host Immune System Number of Pathogenic Cells encountered by the Host Infectious Dose Dr.T.V.Rao MD 36

37. Virulence Factors and Toxins Enzymatic Virulence Factors Examples: Coagulase ( Staphylococcus aureus ) Streptokinase ( Streptococcus pyogenes ) Hyaluronidase (Many pathogens) Collagenase (Many pathogens) Leukocidin (Many pathogens) Hemolysin (Many pathogens) Dr.T.V.Rao MD 37

38. Virulence Factors and Toxins Adhesion Factors Examples: Protein A ( Staphylococcus aureus ) Protein M ( Streptococcus pyogenes ) Dr.T.V.Rao MD 38

39. Virulence Factors Virulence factors help bacteria to (1) invade the host, (2) cause disease, and (3) evade host defences. The following are types of virulence factors : Adherence Factors: Many pathogenic bacteria colonize mucosal sites by using pili (fimbriae) to adhere to cells .

40. Virulence Factors Invasion Factors : Surface components that allow the bacterium to invade host cells can be encoded on plasmids, but more often are on the chromosome . Capsules: Many bacteria are surrounded by capsules that protect them from opsonisation and phagocytosis

41. Virulence Factors and Toxins Exotoxins A type of bacterial toxin with the following properties: May be produced by either gram-positive or gram-negative bacteria Is secreted by the bacteria The action of the exotoxin does not necessarily require the presence of the bacteria in the host Most exotoxins are peptide or protein Most exotoxins are heat sensitive (exception: enterotoxin of Staphylococcus aureus ) Dr.T.V.Rao MD 41

42. Virulence Factors and Toxins Exotoxins (cont.) Classes of exotoxins: Neurotoxic, cytotoxic, or enterotoxic exotoxins Neurotoxins: Interfere with proper synaptic transmissions in neurons Cytotoxins: Inhibit specific cellular activities, such as protein synthesis Enterotoxins: Interfere with water reabsorption in the large intestine; irritate the lining of the gastrointestinal tract Dr.T.V.Rao MD 42

43. Virulence Factors and Toxins Endotoxins A type of bacterial toxin having the following properties: Produced only by gram-negative bacteria Endotoxins are a component of the gram-negative cell wall The action of endotoxin requires the presence of the bacteria in the host. The endotoxin may be released from the cell wall as the cells die and disintegrate Dr.T.V.Rao MD 43

44. Virulence Factors and Toxins Endotoxins (cont.) Endotoxin is composed of Lipid A: Part of the lipopolysaccharide layer Mode of action: Irritation/inflammation of epithelium, GI irritation, capillary/blood vessel inflammation, hemorrhaging Dr.T.V.Rao MD 44

45. Endotoxins Endotoxins: The lipopolysaccharide endotoxins on Gram-negative bacteria cause fever, changes in blood pressure, inflammation, lethal shock, and many other toxic events.

46. Mechanism of Endotoxin activity

47. Exotoxins Exotoxins: Exotoxins include several types of protein toxins and enzymes produced and/or secreted from pathogenic bacteria. Major categories include cytotoxins, neurotoxins, and enterotoxins.

48. Exotoxins Exotoxins, unlike the lipopolysaccharide endotoxin, are protein toxins released from viable bacteria. They form a class of poisons that is among the most potent, per unit weight, of all toxic substances. Most of the higher molecular-sized exotoxin proteins are heat labile; however, numerous low molecular-sized exotoxins are heat-stable peptides. Unlike endotoxin, which is a structural component of all Gram-negative cells, exotoxins are produced by some members of both Gram-positive and Gram-negative genera.

49. E xotoxins The functions of these exotoxins for the bacteria are usually unknown, and the genes for most can be deleted with no noticeable effect on bacterial growth. In contrast to the extensive systemic and immune-system effects of endotoxin on the host, the site of action of most exotoxins is more localized and is confined to particular cell types or cell receptors.

50. Exotoxins Tetanus toxin, for example, affects only intern uncial neurons. In general, exotoxins are excellent antigens that elicit specific antibodies called antitoxins. Not all antibodies to exotoxins are protective, but some react with important binding sites or enzymatic sites on the exotoxin, resulting in complete inhibition of the toxic activity (i.e., neutralization).

51. Exotoxins Endotoxin is comprised of toxic lipopolysaccharide components of the outer membrane of Gram-negative bacteria (see Ch. 2). Endotoxin exerts profound biologic effects on the host and may be lethal. Because it is omnipresent in the environment, endotoxin must be removed from all medical supplies destined for injection or use during surgical procedures.

52. Exotoxins The term endotoxin was coined in 1893 by Pfeiffer to distinguish the class of toxic substances released after lysis of bacteria from the toxic substances (exotoxins) secreted by bacteria. Few, if any, other microbial products have been as extensively studied as bacterial endotoxins. Perhaps it is appropriate that a molecule with such important biologic effects on the host, and one produced by so many bacterial pathogens, should be the subject of intense investigation.

53. Other Factors Plasmids Bacteriophages Compatibility

54. Other Bacterial factors Coagulase Fibrinolysin Hyaluronidase

55. Bacterial Appendages Biofilms Free floating bacteria come in contact with medical devices and attach to them with pili

56. Infecting Dose Minimum infective dose Minimal lethal dose

57. Types of Infectious diseases Bacteraemia Septicaemia Pyemia

58. Other types Endemic disease Epidemic disease Pandemic disease

59. Hospital acquired infections Infection which was neither present nor incubating at the time of admission Includes infection which only becomes apparent after discharge from hospital but which was acquired during hospitalisation (Rcn, 1995) Also called nosocomial infection Dr.T.V.Rao MD 60

60. Basic steps in Prevention of Infection There are possible treatment and prevention to stop the infection cycle. This is through adequate hygiene, sanitary environment maintenance and health education. Dr.T.V.Rao MD 61

61. Antimicrobial agents In Infection Anti-infective drugs such as antibiotics, antiviral, antifungal and ant tubercular drugs suppress infection. It can be administered by mouth, topically or intravenously depending on the infection extent and severity. Sometimes, if drug resistance is known, multiple drugs are used to stop drug resistance and increase drug effectiveness. Antibiotics only work for bacterial infection and have no effect on viral ones. Dr.T.V.Rao MD 62

62. INSPITE OF MANY ADVANCES THERE IS NO STEP GREATER THAN HAND WASHING IN CONTROL OF INFECTIOUS DISEASES

63. Program Created by Dr.T.V.Rao MD for Medical and Paramedical Professional for Global education on Infectious Diseases Email [email protected]