1 / 67

Infectious Diseases

Infectious Diseases. General Principles. Categories Special techniques for diagnosing Table 8-2 New and e merging diseases Table 8-3 Agents of bioterrorism Transmission and dissemination of microbes How microorganisms cause disease Immune evasion by microbes

oki
Télécharger la présentation

Infectious Diseases

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Infectious Diseases

  2. General Principles • Categories • Special techniques for diagnosing Table 8-2 • New and emerging diseases Table 8-3 • Agents of bioterrorism • Transmission and dissemination of microbes • How microorganisms cause disease • Immune evasion by microbes • Infections in immunosuppressed hosts • Spectrum of inflammatory responses to infection

  3. Categories • Prions • Viruses • Bacteria • Fungi • Protozoa • Helminths • Ectoparasites • Table 8-1 Classes of Human Pathogens and their Lifestyles

  4. Agents of Bioterrorism • Category A • Highest risk • Readily disseminated or transmitted • High mortality • Major public health impact • Category B • Moderately easy to disseminate • Moderate morbidity, low mortality • Require specific diagnosis • Require disease surveillance • Category C • Emerging pathogens

  5. Transmission and Dissemination of Microbes • Routes of entry • Spread and dissemination • Release of microbes from the body • Sexually transmitted infections • Healthcare-associated infections –”nosocomial” • Host defenses against infection- innate and adaptive immune defenses

  6. Routes of Entry of Microbes • Microbes can enter by: • Inhalation • Ingestion • Sexual transmission • Insect or animal bites • Injection

  7. Skin • Dense, keratinized outer layer is natural barrier to infection • Low pH and presence of fatty acids inhibit growth of microorganisms • Most organisms enter through breaks in the skin

  8. GI tract • Most GI pathogens are transmitted by food or drink contaminated with fecal material • Normal defenses • Acidic gastric secretions • Layer of viscous mucous covering the intestinal epithelium • Lytic pancreatic enzymes and bile detergents • Defensins =mucosal antimicrobial peptides • Normal flora • Secreted IgA antibodies from MALT • Infections via the GI tract our when local defenses are weakened or the organisms develop strategies to overcome these defenses

  9. Respiratory Tract • Large number of organisms are inhaled daily often in dust or aerosol particles • Distance they travel in inversely proportional to their size • Microorganisms that invade the normal healthy respiratory tract have developed specific mechanisms to: • Overcome mucociliary defenses • Avoid destruction by alveolar macrophages

  10. Urogenital Tract • Almost always invaded from the exterior via the urethra • Regular flushing of urine serves as a defense • Short urethra in females, obstruction, reflux • Lactobacilli in vagina

  11. Spread and Dissemination of Microbes • Proliferate locally at the site of infection • Penetrate the epithelial barrier • Spread to distant sites via • Lymphatics • Blood • Nerves • Major manifestations may appear at sites different from the point of entry • Placental-fetal route

  12. Release of Microbes from the Body • Person-to-person transmission • Respiratory • Fecal-oral • Sexual • Blood and blood products • Animal to human • Direct contact • Consumption of animal products • Indirectly through an invertebrate vector

  13. Sexually Transmitted Infections • Infections with one STI-associated organism increases the risk for additional STIs • The microbes that cause STIs can be spread from a pregnant woman to the fetus and cause severe damage to the fetus or child

  14. How Microorganisms cause Disease • Mechanisms of viral injury • Mechanisms of bacterial injury • Injurious effects of host immunity

  15. Mechanisms of Viral Injury • Directly damage cells by entering them and replicating at the host’s expense • Tropism= predilection for viruses to infect certain cells • A major determinant of tissue tropism is the presence of viral receptors on host cells • Direct cytopathic effects • Antiviral immune responses • Transformation of infected cells • Figure 8-5

  16. Mechanisms of Bacterial Injury • Bacterial virulence • Damage to host tissues depends on the ability of the bacteria to: • Adhere to host cells – adhesins, pili • Invade cells and tissues • Deliver toxins • Virulence genes • Pathogenicity islands • Plasmids and bacteriophages • Quorum sensing • Biofilms

  17. Bacterial Toxins • Endotoxin – LPS of Gram negatives • Exotoxins • Enzymes • Toxins that alter intracellular signaling or regulatory pathways • Neurotoxins • Superantigens

  18. Immune Evasion by Microbes • Replication in sites that are inaccessible to the host immune response • Varying the antigens they express: • High mutation rate • Genetic reassortment • Genetic rearrangement • Large diversity of serotypes

  19. Immune Evasion by Microbes • Methods for evading the innate immune defenses • Produce molecules that inhibit innate immunity • Produce factors that decrease recognition of infected cells by CD4+ helper T cells and CD8+ cytotoxic T cells

  20. Spectrum of Inflammatory Responses to Infection • Suppurative (purulent) inflammation • Mononuclear and granulomatous inflammation • Cytopathic-Cytoproliferative reaction • Tissue necrosis • Chronic inflammation and scarring

  21. Viral Infections • Acute (transient) infections • Chronic (latent) infections • Chronic productive infections – Hepatitis B Virus • Transforming infections

  22. Acute Transient Infections • Measles • Mumps • Poliovirus • West Nile virus • Viral hemorrhagic fevers

  23. Measles • Rubeola • Important cause of death in malnourished children • ssRNA virus – paramyxovirus family • Croup, pneumonia, diarrhea with protein-losing enteropathy, keratitis with scarring and blindness, encephalitis, hemorrhagic measles • Subacutesclerosingpanencephalitis (SSPE) • Rash, Koplik spots, Warthin-Finkeldy cells

  24. Mumps • Paramyxovirus family • Parotitis, orchitis, pancreatitis, encephalitis

  25. Poliovirus • Enterovirus • Fecal-oral route of spread • Most infections are asymptomatic • Spinal poliomyelitis • Bulbar poliomyelitis

  26. West Nile Virus • Arbovirus • Mosquitos – birds • Most infections are asymptomatic • Meningitis and/or encephalitis -1/150 clinically apparent cases

  27. Viral Hemorrhagic Fevers • Four different RNA viruses • Systemic infections • Animal or insect vector

  28. Chronic Latent Infections • ds-DNA viruses • Herpes simplex Virus • Varicella-Zoster Virus • Cytomegalovirus

  29. Herpes Simplex Virus • Fever Blisters or cold sores • Gingivostomatitis • Genital herpes • Corneal lesions- keratitis • Encephalitis • Kaposi varicelliform eruption • Eczema herpeticum • Esophagitis • Bronchopneumonia • Hepatitis

  30. Varicella-Zoster • Chickenpox – acute • Crops of lesions from dew drop on a rose petal to vesicle to crusted lesion • Shingles – reactivation of latent • Ramsey hunt syndrome –geniculate nucleus • Dermatomal • Pain as well as rash

  31. CMV • Asymptomatic • Mononucleosis-like syndrome • Devastating systemic infection in neonates and immunocompromised hosts • Transmission • Transplacental • Neonatal • Saliva • Venereal • Iatrogenic

  32. Transforming Infections • Epstein-Barr Virus • Figure 8-16 – outcome of EBV infection • X-linked lymphoproliferation syndrome (Duncan disease) • Diagnosis • Lymphocytosis with atypical lymphocytes • Postiveheterophile antibody reaction (monospot) • Specific antibodies to EBV antigens

  33. Bacterial Infections • Gram-positive bacteria • Gram-negative bacteria • Mycobacteria • Spirochetes • Anaerobic bacteria • Obligate intracellular bacteria

  34. Gram-Positive • Staphococcal infections • Streptococal and Enterococcal infections • Diphtheria • Listeriosis • Anthrax • Nocardia

  35. Staphylococcal Infections • Staph. Aureus • Pyogenic infections • Skin lesions – impetigo, furuncle, carbuncle, hidradenitis, paronchyia, felons, staph scalded skin syndrome (Ritter disease) • Abscesses • Sepsis • Osteomyelitis • Pneumonia • Endocarditis • Multitude of virulence factors • MRSA • Superantigens • Food poisoning • Toxic shock syndrome

  36. Streptococcal Infections • S. pyogenes (Group A) • Pharyngitis, scarlet fever, erysipelas, impetigo, rheumatic heart disease, TSS, glomerulonephritis • S. agalactiae (Group B) • Neonatal sepsis, chorioamnionitis • S. pneumoniae • Lobar pneumonia • S. mutans • Dental decay • Enterococci • Endocarditis and UTIs

  37. Diphtheria • Skin lesions in infected wounds • Formation of a tough pharyngeal membrane • Toxin-mediated damage to heart, nerves and other organs

  38. Listeria • Food-borne illnesses • Pregnant woman, neonates, elderly, and immunosuppressed • Meningitis

  39. Anthrax • Cutaneous • Inhalational • Gastrointestinal • Exposure to animals or animal products such as hides and wool • Spores can be ground into a fine powder making a potent biologic weapon

  40. Nocardia • Similar to molds – branching filaments • Opportunistic infections in immunocompromised hosts

  41. Gram-Negative • Neisserial Infections • Whooping Cough • Pseudomonas Infections • Plague • Chancroid • Granuloma Inguinale

  42. Neisserial Infections • Gram-negative diplococci, coffee bean, chocolate agar • N.meningitidis – meningitis, common colonizer of the oropharynx, complement important in immune response • N. gonorrhoeae – STD, 2nd after chlamydia, urethritis in men, often asymptomatic in women  PID  infertility and ectopic pregnancy • Antigenic variation allows escape from the immune response • Multiple serotypes • Pili proteins and OPA proteins

  43. Whooping Cough • Gram-negative coccobacillius • Bordetella pertussis • Highly contagious • Violent paroxysms of coughing • Inspiratory “whoop” • Laryngotracheobronchitis • Severe cases – bronchial mucosal erosion, hyperemia, copious mucopurulent exudate • Striking peripheral lymphocytosis • Hypercellularity and enlargement of the mucosal lymph follicles and peribronchial lymph nodes • No pneumonia unless superinfected

  44. Pseudomonas Infection • Opportunistic gram-negative bacillus • Cystic fibrosis, severe burns, neutropenia • Pili, adherence proteins, endotoxin, exotoxin, , enzymes, iron-containing compounds • Necrotizing pneumonia, vasculitis • Ecthymagangrenosum • DIC

  45. Plague • Yersinia pestis • Gram-negative intracellular bacterium • Fleas  rodents  humans • Yopvirulon - kills host phagocytes • Plague • Bubonic plague • Pneumonic plague • Septicemic plague

  46. Chancroid • Soft chancre • Hemophilusducreyi • Tropics – one of the most common causes of genital ulcers in Africa and Southeast Asia

  47. Granuloma Inguinale • Klebsiellagranulomatis • Chronic inflammatory disease • Tropics • Extensive scarring and lymph obstruction • Psuedoepitheliomatous hyperplasia

  48. Mycobacteria • Tuberculosis • Mycobacterium avium-intracellulare Complex • Leprosy

  49. Tuberculosis • Mycobacterium tuberculosis • TB flourishes where there is poverty, crowding, and chronic debilitating illness. HIV • Differentiate infection from disease • Most primary TB is asymptomatic • Pathogenesis – Figure 8-27 • Clinical Features – Figure 8-28 • Fever, night sweats, hemoptysis • Ghon complex, Pott disease, intestinal TB – unpasteruerized milk

  50. Mycobacterium avium-intracellulare Complex • MAC • AIDS, CD4+ counts < 60/mm3 • Fever, night sweats, weight loss • Abundant acid-fast organisms within macrophages • Lungs, lymph nodes, liver, spleen

More Related