Chapter 21

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Chapter 21

  1. 1. Miscellaneous Bacterial Agents of Disease Chapter 21
  2. 2. spirochetes <ul><li>Gram negative human pathogens </li></ul><ul><li>Treponema </li></ul><ul><li>Leptospira </li></ul><ul><li>Borrella </li></ul>
  3. 3. Treponema <ul><li>thin, coiled cells </li></ul><ul><li>live in the oral cavity, intestinal tract, & perigenital regions of humans & animals </li></ul><ul><li>Pathogenic species are strict parasites </li></ul>
  4. 4. Treponema pallidum <ul><li>human is the natural host </li></ul><ul><li>extremely fastidious & sensitive, cannot survive long outside of the host </li></ul><ul><li>causes syphilis </li></ul><ul><li>Primary syphilis </li></ul><ul><li>Secondary syphilis </li></ul><ul><li>Tertiary syphilis </li></ul><ul><li>Congenital syphilis – nasal discharge, skin eruptions, bone deformation, nervous system abnormalities </li></ul><ul><li>treatment: penicillin G </li></ul>
  5. 5.
  6. 6. Chancre
  7. 7. Darkfield Microscopy
  8. 8. Leptospira <ul><li>tight, regular individual coils with a bend or hook at one or both ends </li></ul><ul><li>L. biflexa – harmless, free-living saprobe </li></ul><ul><li>L. interrogans – causes leptospirosis, a zoonosis </li></ul><ul><ul><li>bacteria shed in urine; infection occurs by contact; targets kidneys, liver, brain, eyes </li></ul></ul><ul><ul><li>sudden high fever, chills, headache, muscle aches, conjunctivitis, & vomiting </li></ul></ul><ul><ul><li>50-60 cases a year in US </li></ul></ul>
  9. 9. Borrella <ul><li>large, 3-10 coils </li></ul><ul><li>Borrelioses transmitted by arthropod vector </li></ul><ul><li>B. hermsii - relapsing fever </li></ul><ul><li>B. burgdorferi - Lyme disease </li></ul>
  10. 10. B. hermsii - relapsing fever <ul><li>mammalian reservoirs –squirrels, chipmunks, wild rodents </li></ul><ul><li>tick-borne </li></ul><ul><li>after 2-15-day incubation, patients have high fever, shaking, chills, headache, & fatigue </li></ul><ul><li>nausea vomiting, muscle aches, abdominal pain; extensive damage to liver, spleen, heart, kidneys, & cranial nerves </li></ul><ul><li>parasite changes & immune system tries to control it- recurrent relapses </li></ul><ul><li>tetracycline </li></ul>
  11. 11.
  12. 12. B. burgdorferi - Lyme disease <ul><li>transmitted by ticks </li></ul><ul><li>complex 2-year cycle involving mice & deer </li></ul><ul><li>nonfatal, slowly progressive syndrome that mimics neuromuscular & rheumatoid conditions </li></ul><ul><li>70% get bull’s eye rash </li></ul><ul><li>fever, headache, stiff neck, & dizziness </li></ul><ul><li>if untreated can progress to cardiac & neurological symptoms, polyarthritis </li></ul><ul><li>tetracycline, amoxicillin </li></ul><ul><li>vaccine for dogs, human vaccine discontinued </li></ul><ul><li>Prevention-insect repellant containing DEET </li></ul>
  13. 13. Life Cycle of Ixodes Figure 21.18
  14. 14.
  15. 15. Lyme disease
  16. 16. Vibrio cholera <ul><li>comma-shaped </li></ul><ul><li>One of top 7 causes of morbidity & mortality </li></ul><ul><li>ingested with food or water </li></ul><ul><li>infects surface of small intestine, noninvasive </li></ul><ul><li>cholera toxin causes electrolyte & water loss through secretory diarrhea (“rice-water” stool), resulting dehydration leads to muscle, circulatory, & neurological symptoms </li></ul><ul><li>treatment: oral rehydration , tetracycline </li></ul><ul><li>vaccine </li></ul>
  17. 17. Vibrio cholera
  18. 18. Action of Cholera Toxin Figure 21.25
  19. 19. other Vibrio <ul><li>salt-tolerant inhabitants of coastal waters, associate with marine invertebrates </li></ul><ul><li>Vibrio parahaemolyticus – gastroenteritis from raw seafood </li></ul><ul><li>Vibrio vulnificus - gastroenteritis from raw oysters </li></ul>
  20. 20. Campylobacter jejuni <ul><li>important cause of bacterial gastroenteritis </li></ul><ul><li>transmitted by beverages & food (poultry most common) </li></ul><ul><li>reach mucosa at the last segment of small intestine near colon; adhere, burrow through mucus and multiply </li></ul><ul><li>symptoms of headache, fever, abdominal pain, bloody or watery diarrhea that is self-limiting </li></ul><ul><li>heat-labile enterotoxin </li></ul>
  21. 21. Campylobacter jejuni
  22. 22. Helicobacter pylori <ul><li>Curved cells discovered in 1979 in stomach biopsied specimens </li></ul><ul><li>Slightly helical, highly motile bacterium that colonizes the stomach of its hosts </li></ul><ul><li>Causes gastritis and most (if not all) peptic ulcers </li></ul><ul><li>H. pylori produces numerous virulence factors that enable it to colonize the stomach </li></ul>
  23. 23. H. pylori and Peptic Ulcers Figure 21.27.1
  24. 24. H. pylori and Peptic Ulcers Figure 21.27.2
  25. 25. H. pylori and Peptic Ulcers Figure 21.27.3
  26. 26. Diagnosis, Treatment, and Prevention <ul><li>Diagnosis </li></ul><ul><ul><li>Presence of H. pylori can be demonstrated by a positive urease test </li></ul></ul><ul><ul><li>Biochemical tests provide a definitive identification </li></ul></ul><ul><li>Treatment </li></ul><ul><ul><li>Antimicrobial drugs are used in combination with drugs that inhibit acid production </li></ul></ul><ul><li>Prevention </li></ul><ul><ul><li>Prevention involves good hygiene, adequate sewage treatment, water purification, and proper food handling </li></ul></ul>
  27. 27. Rickettsia <ul><li>obligate intracellular parasites </li></ul><ul><li>gram-negative cell wall </li></ul><ul><li>among the smallest bacteria </li></ul><ul><li>nonmotile pleomorphic rods or coccobacilli </li></ul><ul><li>ticks, fleas & louse are involved in their life cycle </li></ul><ul><li>bacteria enter endothelial cells & cause necrosis of the vascular lining – vasculitis, vascular leakage & thrombosis </li></ul><ul><li>treat with tetracycline & chloramphenicol </li></ul>
  28. 28. 4 types of rickettsioses <ul><li>epidemic typhus – R. prowazekii carried by lice; starts with a high fever, chills, headache, rash; May have a chronic, recurrent form </li></ul><ul><li>endemic typhus – R. typhi , harbored by mice & rats; occurs sporadically in areas of high flea infestation; milder symptoms </li></ul><ul><li>Rocky Mountain spotted fever – R. rickettsii zoonosis carried by dog & wood ticks; most cases on eastern seaboard; distinct spotted rash; may damage heart & CNS </li></ul><ul><li>Ehrlichia genus contains 2 species of rickettsias; tickborne bacteria cause human monocytic & granulocytic ehrlichiosis </li></ul>
  29. 29. Rocky Mountain Spotted Fever
  30. 30. Rocky Mountain Spotted Fever Rickettsia rickettsii Distribution of cases over a 4-year period
  31. 31. Coxiella burnetti <ul><li>causes Q fever </li></ul><ul><li>intracellular parasite </li></ul><ul><li>produces an unusual resistant spore </li></ul><ul><li>harbored by a wide assortment of vertebrates & arthropods </li></ul><ul><li>transmitted by air, dust, unpasteurized milk, ticks </li></ul><ul><li>usually inhaled causing pneumonitis, fever, hepatitis </li></ul><ul><li>tetracycline treatment </li></ul><ul><li>vaccine available </li></ul>
  32. 32. Coxiella burnetti
  33. 33. Bartonella <ul><li>small gram-negative, fastidious, cultured on blood agar </li></ul><ul><li>Bartonella -caused diseases </li></ul><ul><ul><li>trench fever, spread by lice </li></ul></ul><ul><ul><li>cat-scratch disease, a lymphatic infection associated with a clawing injury by cats. </li></ul></ul><ul><ul><ul><li>Organism carried by 40% of cats </li></ul></ul></ul><ul><ul><ul><li>Most infections localized and resolve a a couple weeks </li></ul></ul></ul><ul><ul><li>bacillary angiomatosus in AIDS patients </li></ul></ul><ul><li>tetracycline, erythromycin & rifampin </li></ul>
  34. 34. Cat-scratch disease Bartonella henselae
  35. 35. Chlamydia <ul><li>obligate intracellular parasites </li></ul><ul><li>small gram-negative cell wall </li></ul><ul><li>C. pneumoniae – causes an atypical pneumonia that is serious in asthma patients </li></ul><ul><li>C. psittaci – causes ornithosis, a zoonosis transmitted to humans from bird vectors; highly communicable among all birds; pneumonia or flulike infection with fever, lung congestion </li></ul>
  36. 36. Chlamydia trachomatis <ul><li>human reservoir </li></ul><ul><li>2 strains </li></ul><ul><li>trachoma strain– attacks the mucous membranes of the eyes, genitourinary tract & lungs </li></ul><ul><ul><li>ocular trachoma – uncommon in U.S. but common in Africa and Asia. Severe infection, deforms eyelid & cornea, may cause blindness </li></ul></ul><ul><ul><li>inclusion conjunctivitis – occurs as babies pass through birth canal; prevented by prophylaxis </li></ul></ul><ul><ul><li>STD – urethritis, cervicitis, salpingitis (PID),infertility, scarring </li></ul></ul><ul><li>lymphogranuloma venereum strain– disfiguring disease of the external genitalia & pelvic lymphatics </li></ul>
  37. 37. Chlamydia trachomatis Lymphogranuloma venereum lesion Trachoma
  38. 38. Mycoplasma <ul><li>naturally lack cell walls, highly pleomorphic </li></ul><ul><li>treated with tetracycline, erthyromycin </li></ul><ul><li>M. pneumoniae – primary atypical pneumonia; pathogen slowly spreads over interior respiratory surfaces, causing fever, chest pain & sore throat. </li></ul><ul><li>M. hominis & Ureplasma urealyticum – weak sexually transmitted pathogens </li></ul>
  39. 39. Bacteria in dental disease <ul><li>oral cavity is a complex, dynamic ecosystem, containing 400 species </li></ul><ul><li>dental caries – slow progressive infection of irregular areas of enamel surface </li></ul><ul><ul><li>begins with colonization by slime-forming species of Streptococcus & cross adherence with Actinomyces </li></ul></ul><ul><ul><li>process forms layer of thick, adherent material (plaque) that harbors masses of bacteria which produce acid that dissolves enamel </li></ul></ul><ul><ul><li>If plaque is allowed to stay, secondary invaders appear – Lactobacillus, Bacteroides, Fusobacterium, Porphyromonas, Treponema. </li></ul></ul><ul><ul><li>Acid dissolves tooth enamel </li></ul></ul>
  40. 40.
  41. 41. Thin mucous coating of salivary proteins Streptococcus mutans Secondary invaders
  42. 42. Peridontal disease <ul><li>soft tissue disease </li></ul><ul><li>when plaque becomes calcified into calculus above and below the gingiva </li></ul><ul><li>this irritates tender gingiva causing inflammation – gingivitis </li></ul><ul><li>pockets between tooth & gingiva are invaded by bacteria (spirochetes & gram-negative bacilli) </li></ul><ul><li>tooth socket may be involved (peridontitis) </li></ul><ul><li>tooth may be lost </li></ul>

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