Introduction to Infectious Diseases and Bacterial Infections


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Pathology Lecture given August 17, 2011
by Noel C. Santos, M.D.
AUF School of Medicine, Dept. of Pathology

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Introduction to Infectious Diseases and Bacterial Infections

  1. 1. Infectious Disease<br />By Noel C. Santos, M.D.<br />
  2. 2. Spectrum of Inflammatory Response to Infection<br />Suppurative (PMN) Inflammation<br />Mononuclear and Granulomatous Inflammation<br />Cytopathic-Cytoproliferative Inflammation<br />Necrotizing Inflammation<br />Chronic Inflammation and Scarring<br />
  3. 3. SUPPURATIVE INFLAMMATION<br />Purulent, abscess, liquefaction necrosis<br />
  8. 8. DIAGNOSING INFECTION<br />History<br />Physical Examination<br />Laboratory Examination<br />Direct Evidence: demonstration of the organism<br />Indirect Evidence: exposure or response (immunologic or Ab)<br />
  9. 9. Special Techniques for Diagnosing<br />Infectious Agents<br />Gram stain Most bacteria<br />Acid-fast stain Mycobacteria, nocardiae<br />Silver stains Fungi, legionellae,<br />pneumocystis<br />Periodic acid-Schiff Fungi, amebae<br />MucicarmineCryptococci<br />GiemsaCampylobacteria,<br />leishmaniae, malaria<br />Antibody probes Viruses, rickettsiae<br />Culture All classes<br />DNA probes Viruses, bacteria, protozoa<br />
  10. 10. DEMONSTRATION OF THE ORGANISM<br />Microscopy<br />Culture<br />Histology<br />Immunologic (Ab & Ag)<br />DNA (PCR)<br />
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  12. 12. Gram Stain<br />Gram Positive: violet to black<br />Gram Negative: pink to red<br />COCCI<br />BACILLI<br />
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  18. 18. Other Staining Techniques<br />Acid Fast Stain<br />Chemical Stains<br />Negative “Stain”<br />
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  22. 22. Histopathologic Examination<br />Routine H & E stain<br />Histo/Cyto Chemical stains<br />PAS<br />Silver stains<br />Reticulin stains<br />
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  33. 33. EXPOSURE or RESPONSE (IMMUNOLOGIC)<br />In-vivo: skin (dermal) tests<br />In-vitro: serological tests<br /><ul><li>Nonspecific tests: VDRL, HIV screening, etc. (SCREENING)
  34. 34. Specific tests: TPFA, Western/Southern blot (DIAGNOSTIC)</li></li></ul><li><ul><li>35 y/o male
  35. 35. Non-painful lesion in the genitalia
  36. 36. Sexual contact 3 weeks ago
  37. 37. How will you directly demonstrate the organism?
  38. 38. How will you indirectly demonstrate the patient’s exposure to the organism?</li></li></ul><li>Facial skin lesions<br />
  39. 39.
  40. 40.
  41. 41. HIV patient, male, homosexual<br />Difficulty of swallowing<br />
  42. 42.
  43. 43.
  44. 44. Few days later developed dyspnea with gelatinous sputum<br />
  45. 45. Later died……<br />
  46. 46.
  47. 47. Media man with high grade fever, chills, body ache<br />Headache later developed seizures<br />Transported to US and later died<br />
  48. 48. Plasmodium vivax<br />Plasmodium falciparum<br />
  49. 49. 25 year-old male<br />Flu-like syndrome: fever, body malaise, body ache<br />Lymph node enlargement<br />
  50. 50. INFECTIOUS DISEASE<br />Causative Agents<br />Mode of Transmission<br />How microbes cause disease?<br />How the host responds?<br />Immunologically<br />Inflammatory response<br />How to approach?<br />History and physical examination<br />What useful laboratory methods to use?<br />CORRECT DIAGNOSIS<br />PROPER TREATMENT<br />
  52. 52. Mechanisms of Bacteria Induced Injury<br />Fast-growers deprive the host tissues of nutrients, and lower tissue pH.<br />Many bacteria produce one or more factors<br />leukocidins, hemolysins, hyaluronidases, coagulases, fibrinolysins, and enzymesexotoxins<br />Broken-down cell walls release endotoxins (lipopolysaccharide protein complexes) which cause high fever, capillary permeability, shock, DIC.<br />
  53. 53. Respiratory Infections<br />Viral Respiratory infections<br />Bacterial Respiratory infections <br />Haemophilus Influenza<br />Tuberculosis<br />Fungal Respiratory infections<br />
  54. 54. HaemophilusInfluenzae Infection<br />This coccobacillus causes infections (especially meningitis and pneumonia) in children who are not fully immune-protected <br />Older children are more prone to conjunctivitis ("pink eye")<br />epiglottitis("croup") laryngotracheobronchitis<br />
  55. 55. HaemophilusInfluenzae Infection<br />The most virulent strain is type B, which has a capsule. <br />With the introduction of the Hib vaccine for toddlers, the occurrence of serious H. flu B infections has dropped 71%<br />
  56. 56. Clinical spectrum HaemophilusInfluenzae Infection<br />acute epiglottitis - may suffocate the child less than 24 hours <br />H. Influenzae pneumonia - pediatric emergency may result in airway obstruction, high mortality rate<br />May cause suppurative meningitis < 5 years old <br />acute conjunctivitis<br />
  57. 57. Tuberculosis<br />infects 1/3 of world population<br />kills 3 million patients each year<br />resurgence of MTB because of AIDS<br />increased in MDRTB slow to grow<br />mutation in the RNA polymerase and catalase<br />
  58. 58. Mycobacterium<br />aerobic, non spore forming , non motile <br />with waxy coat - acid fastness <br />M. tuberculosis (inhalation of infective droplets) <br />M bovis ( drinking infected milk)<br />M. avis and M. intracellulare - no virulence <br />M. leprae - leprosy <br />
  59. 59. Types of Tuberculosis<br />Primary Infection<br />Secondary Infection<br />Disseminated Tuberculosis<br />
  60. 60. Primary Tuberculosis<br />Begins with inhalation of MTB and ends with T cell mediated response. + PPD test <br />3 ways by which Mycobacteria activated T cells interacts with macrophages <br />helper T cells secrete interferon <br />suppressor T cells lyse macrophages infected cells<br />CD4 - and CD 8 - cells lyse macrophage<br />Ghon’s complex<br />
  61. 61. Secondary Tuberculosis<br />Reinfection or reactivation of dormant disease. <br />Most often occurs in the apex of lung <br />two features are caseous necrosis and cavities<br />
  62. 62. Mophology of MTB<br />Chronic ganulomatous inflammation with caseation necrosis.<br />Miliary TB - hematogenous dissemination of Tbculous lesion <br />small yellow white - millet seeds<br />most frequent in lung, lymph nodes meninges<br />
  63. 63. Mycobacterial infection in AIDS patients<br />HIV infected T cells and macrophages - failure to kill mycobacterium<br />Granuloma are less well formed <br /> are more necrotic<br />contains more abundant acid fast organisms. <br />
  64. 64. Gastrointestinal Infections<br />Viral Enteritis <br />Bacterial Enteritis<br />Shigella bacillary dysentery<br />Typoid fever<br />Cholera<br />Parasitic Intestinal Infection<br />
  65. 65. Three Mechanisms of bacterial diarrhea <br />1.They can invade the gut wall directly. Diarrhea results from the inflammatory exudate, and the stools will contain polys. <br />2.They can release enterotoxins, either into the gut or into food.<br /> 3.They can attach to mucosal cells and cause them to secrete too much water ("enteroadhesive bacteria"). <br />
  66. 66. Shigella Bacillary Dysentery<br />Dysentery refers to diarrhea with abdominal cramps and tenesmus stools with mucus and blood <br />caused by <br />Shigelladysenteriae<br />S. flexneri<br />S. boydii<br />S. sonnei. <br />Gram negative facultative anaerobes<br />
  67. 67. Pathogenesis of Shigella Bacillary Dysentery<br />transmission - fecal oral route <br />Shigella bacteria invades mucosal cells <br />dysentery occurs when bacteria escape phagolysosome and destroy host cells.<br />Shiga toxin - causes hemorrhagic colitis and HUS ( binds to glycolipids and block protein synthesis) <br />in HLA B 27 - chronic arthritis (Reiter’s syndrome)<br />
  68. 68. Morphology of bacillary dysentery<br />Hyperemic and edematous colonic mucosa<br />enlarged lymphoid follicles<br />fibrinosuppurativeexudate covers mucosa <br />Histology - mononuclear leucocytic infiltrates within l. propia<br />ulcers covered with neutrophilic reaction<br />
  69. 69. Typhoid fever<br />Causative agent Salmonellae flagellated, gram-negative bacteria <br />water and food borne gastroenteritis.<br />Salmonella typhi<br />S. enteritidis<br />S. typhimirium<br />
  70. 70. Pathogenesis of Typhoid fever<br />Invade intestinal epithelial cells controlled by invasion genes and induce by low oxygen tension<br />Invade tissue macrophages induced by acidic pH<br />
  71. 71. Morphology of Typhoid fever<br />S. enteritidis and typhimirium lesion are Iimited to ileum and colon - erosion of epithelium <br />S typhi - proliferation of phagocytes with enlargement of RES - <br />2nd week mucosa over swollen node are shed <br />Histopathology - erythrophagocytosis<br />enlarged spleen, random liver necrosis<br />gallstone<br />
  72. 72. Cholera<br />Vibrio cholera <br />Gram negative bacteria<br />cause of epidemics characterized by watery diarrhea<br />140 serotypes, O1 & O139 severe diarrhea<br />
  73. 73. Pathogenesis of Cholera<br />Do not invade epithelial cells secrete enterotoxin (cholera toxin)<br />flagellar proteins are involved in attachment <br />
  74. 74. Morphology of cholera<br />Do not invade GUT mucosa minor histopathologic changes.<br />Congestion of mucosal lamina propia<br />Mononuclear cell infiltrate<br />Peyer patches hyperplasia.<br />
  75. 75. Staphylococcus<br />are normal inhabitants of the nose and skin of most healthy people. (Their favorite habitat is the hair follicles.) <br />Virulence factors include coagulase,hemolysin, and protein A (which ties up Fcportions of antibodies). <br />
  76. 76. Two types of Staphylococcus<br />Coagulase-positive staphylococcus (Staphylococcus pyogenes var. aureus) is a potent pathogen. <br /> It tends to produce localized infection <br />Coagulase-negative staphylococci (Staphylococcus epidermidis) are skin commensals and opportunists which infect prosthetic heart valves<br />
  77. 77. Staphylococcus<br />It is the chief cause of bacterial skin abscesses. <br />Furuncles are single pimples, while carbuncles are pimple clusters <br />Metastatic infections (most commonly, to the heart valves, kidney or the cavernous sinus) <br />Impetigo is a pediatric infection limited to the stratum corneum of the skin -- look for honey-colored crusts. <br />
  78. 78. Staphylococcal Infections<br />surgical wounds<br />staphylococcal pneumonia<br />Staphylococcal endocarditis -- a destructive infection of the heart valves <br />
  79. 79. Staphylococcal Infections<br />food poisoning due to strains which have produced enterotoxin B, a pre-formed toxin in un-refrigerated meat or milk products<br />Other toxin-related staphylococcal diseases are toxic-shock syndrome (GI upsets, shock, conjunctivitis, rash, liver failure, kidney failure, and loss of skin, <br />
  80. 80. Streptococcus<br />live in the throats of healthy carriers<br />cause sporadic and epidemic human disease. <br />Lancefield groups:<br />
  81. 81. Lancefield groups of Streptococcus<br />Group A: Strep. pyogenes, with many serotypes, is the familiar pathogen of "strep throat", common skin infections<br />Group B: Newborns, less often, severely compromised adults Group D: Enterococcus (lately Strep. fecalis), causes urinary tract infections, as well as endocarditis<br />Strep. bovis sepsis<br />
  82. 82. Streptococcal Infections<br />Streptococcal pharyngitis - is a disease of young people. Complications include retro-pharyngeal abscess, CellulitisLudwig's angina. <br />Scarlet fever - is a strep throat caused erythrogenic toxins. <br />
  83. 83. Streptococcal Infections<br />Streptococcal skin infections may mimic any staphylococcal infections (even impetigo), but spreading cellulitis with obvious lymphangitis ("red streaks") is more typical. <br />Erysipelas is a severe skin infection caused by group A strep; geographic of red, thickened, indurated areas of the skin are characteristic.<br />
  84. 84. Streptococcal Infections<br />Streptococcal toxic-shock syndrome is mistaken for "evidence of child abuse" <br />Phlegmasia alba dolens ("milk leg") - group A strep infection of deep venous thrombi.<br />Streptococcal pneumonia, like its staphylococcal counterpart, often superinfects viral pneumonia. <br />
  85. 85. Streptococcal Infections<br />Post-streptococcal hypersensitivity diseases:<br />rheumatic fever<br />post-streptococcal glomerulonephritis<br />erythemanodosum. <br />
  86. 86. Pneumococcus (Strep. pneumoniae)<br />It caused lobar pneumonia.<br />This is still a common terminal infection in debilitated people, though it can strike the young and healthy <br />pneumococcal bronchopneumonia, middle ear infections, sinusitis, and meningitis <br />Spontaneous pneumococcal peritonitis complicates ascites in cirrhotics and nephrotic syndrome patients. <br />
  87. 87. Pseudomonas<br />"the water bug" <br />famous opportunists that flourish in people exposed to antibiotics that kill other microbes. <br />Pseudomonas infections are especially common on the burn unit, the ears of diabetics, and the blood of those with severe neutropenia. <br />
  88. 88. Pseudomonas<br />The pus may be fluorescent, and grape fragrance is common. <br />Pseudomonas sepsis is often preceded and/or followed by a necrotizing pneumonia. <br />Ecthymagangrenosum is a severe pseudomonas soft tissue infection. <br />bacterial infection centered on the blood vessels, with thrombosis and bleeding, think of a pseudomonas etiology. <br />
  89. 89. Classification of sexually transmitted disease<br /><ul><li>Gonorrhea - Neisseriagonorrhoeae
  90. 90. Chlamydia
  91. 91. Herpes genitalis - HSV-2
  92. 92. Syphilis (Lues) - Treponemapallidum
  93. 93. Yaws - Treponemapallidum, subsppertenue
  94. 94. Lymphogranulomavenereum (LGV) - Chlamydia trachomatis
  95. 95. Granulomainguinale (Donovanosis) - Calymmatobacteriumgranulomatis
  96. 96. Chancroid - Hemophilusducreyi
  97. 97. Benign Genital Warts (Condylomataacuminata) - Human papillomavirus (HPV)
  98. 98. Scabies - Sarcoptesscabiei (itch mite)</li></li></ul><li>Gonorrhea<br /><ul><li>Urethritis,
  99. 99. epididymitis
  100. 100. proctitis
  101. 101. cervicitis
  102. 102. endometritis
  103. 103. salpingitis
  104. 104. perihepatitis
  105. 105. bartholinitis</li></li></ul><li>Gonorrhea<br /><ul><li>conjunctivitis
  106. 106. prepubertal vaginitis
  107. 107. ?prostatitis,
  108. 108. amniotic infection syndrome,
  109. 109. disseminated gonococcal infection,
  110. 110. chorioamnionitis
  111. 111. premature rupture of membranes, and
  112. 112. premature delivery</li></li></ul><li>Chlamydia Trachomatis<br /><ul><li>urethritis, epididymitis, proctitis, cervicitis, endometritis, salpingitis, perihepatitis, bartholinitis, prepubertal vaginitis, otitis media in infants, ?chorioamnionitis, ?premature rupture of membranes, ?premature delivery, inclusion conjunctivitis, infant pneumonia, trachoma, and lymphogranuloma venereum</li></li></ul><li>Other bacterial STD<br />Haemophilus ducreyi - Chancroid <br /> Calymmatobacterium gralumatis - Donovanosis (granuloma inguinale) <br /> Shigella spp - Shigellosis in homosexual men <br /> Campylobacter spp - Enteritis, proctocolitis <br />
  113. 113. Thank you and good morning!!!<br />