Foundations in Microbiology Seventh Edition

Transcription

1 Lecture PowerPoint to accompany Foundations in Microbiology Seventh Edition Talaro Chapter 21 Miscellaneous Bacterial Agents of Disease Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2 21.1 The Spirochetes Gram-negative human pathogens Free living saprobes, or commensals of animals, not primary pathogens Treponema Leptospira Borrelia 2

3 Figure 21.1 Typical spirochete 3

4 Genus Treponema Thin, regular, coiled cells Live in the oral cavity, intestinal tract, and perigenital regions of humans and animals Pathogens are strict parasites with complex growth requirements Require live cells for cultivation 4

5 Treponema Pallidum: The Spirochete of Syphilis Human is the natural host Extremely fastidious and sensitive; cannot survive long outside of the host Sexually transmitted and transplacental 5

6 Pathogenesis and Host Response Spirochete binds to epithelium (mucous membrane or abraded skin), multiplies, and penetrates capillaries Moves into circulation and multiplies Untreated syphilis marked by 3 clinical stages: Primary, secondary, tertiary Spirochete appears in lesions and blood during first 2 stages communicable 6

7 Primary syphilis appearance of hard chancre at site of inoculation; chancre heals spontaneously Secondary syphilis fever, headache, sore throat, red or brown rash on skin, palms, and soles; rash disappears spontaneously Tertiary syphilis about 30% of infections enter in tertiary stage; can last for 20 years or longer; numerous pathologic complications occur in susceptible tissues and organs Neural, cardiovascular symptoms, gummas develop Congenital syphilis nasal discharge, skin eruptions, bone deformation, nervous system abnormalities 7

8 8

9 Figure 21.3 Primary syphilis lesion, chancre 9

10 Figure 21.4 Symptom of secondary syphilis 10

11 Figure 21.5 and 21.6 Manifestations of syphilis 11

12 Figure 21.7 Congenital syphilis 12

13 Diagnosis and Treatment Stages of syphilis mimic other diseases Consider symptoms, history, microscopic, and serological testing RPR, VDRL, FTA-ABS Treatment: penicillin G 13

14 Figure 21.8 Treponema pallidum 14

15 Nonsyphilitic Treponematoses Resemble syphilis; rarely transmitted sexually or congenitally; cutaneous and bone diseases endemic to specific regions Bejel T. pallidum subspecies endemicum; deforming childhood infection of the mouth, nasal cavity, body, and hands Yaws T. pallidum subspecies pertenue; invasion of skin cut, causing a primary ulcer that seeds a second crop of lesions Pinta T. carateum; superficial skin lesion that depigments and scars the skin 15

16 Figure 21.9 Endemic treponematoses 16

17 Leptospira and Leptospirosis Tight, regular individual coils with a bend or hook at one or both ends L. biflexa harmless, free-living saprobe L. interrogans causes leptospirosis, a zoonosis Bacteria shed in urine; infection occurs by contact with contaminated urine; targets kidneys, liver, brain, eyes Sudden high fever, chills, headache, muscle aches, conjunctivitis, and vomiting Long-term infections may affect kidneys and liver cases a year in U.S. 17

18 Borrelia: Arthropod-Borne Spirochetes Large, 3-10 coils irregularly spaced Borrelioses transmitted by arthropod vector B. hermsii relapsing fever B. burgdorferi Lyme disease 18

19 B. Hermsii Relapsing Fever Mammalian reservoirs squirrels, chipmunks, wild rodents Tick-borne After 2-15-day incubation, patients have high fever, shaking, chills, headache, and fatigue Nausea, vomiting, muscle aches, abdominal pain; extensive damage to liver, spleen, heart, kidneys, and cranial nerves Parasite changes and immune system tries to control it Recurrent relapses Tetracycline 19

20 Figure Pattern in relapsing fever 20

21 B. Burgdorferi Lyme Disease Carried by white-footed mouse, transmitted by Ixodes ticks Complex 2-year cycle involving mice and deer Nonfatal, slowly progressive syndrome that mimics neuromuscular and rheumatoid conditions 50-70% get bull s eye rash Fever, headache, stiff neck, and dizziness If untreated can progress to cardiac and neurological symptoms, polyarthritis Tetracycline, amoxicillin Vaccine for dogs, human vaccine discontinued Insect repellant containing DEET 21

22 Figure Cycle of Lyme disease 22

23 Figure Views of Lyme disease skin rash 23

24 21.2 Curviform Gram-Negative Bacteria and Enteric Diseases Three genera: 1. Vibrio comma-shaped rods, single polar flagellum 2. Campylobacter short spirals or curved rods; one flagellum 3. Helicobacter spirochete with tight spirals and several polar flagella 24

25 Vibrio Cholera Comma-shaped, possess unique O and H Ags El Tor biotype: survives longer, more infectious Infectious dose 10 8 Infects mucous barrier of small intestine, noninvasive Cholera toxin causes electrolyte and water loss through secretory diarrhea, rice water stool ; resulting dehydration leads to muscle, circulatory, and neurological symptoms Treatment: oral rehydration, tetracycline Vaccine available 25

26 Figure (a-b) Alterations in intestinal function caused by cholera toxin 26

27 Figure (c) Alterations in intestinal function caused by cholera toxin 27

28 Pathogens Carried by Seafood Salt-tolerant inhabitants of coastal waters, associate with marine invertebrates Vibrio parahaemolyticus gastroenteritis from raw seafood; symptoms similar to cholera Vibrio vulnificus gastroenteritis from raw oysters; serious complications in persons with diabetes or liver disease Treatment fluid and electrolyte replacement; occasionally antimicrobials 28

29 Diseases of the Campylobacter Vibrios Campylobacters slender, curved, or spiral bacilli, often S-shaped or gull-winged pairs Polar flagella Common residents of the intestinal tract, genitourinary tract, the oral cavity of birds and mammals Most important: Campylobacter jejuni C. fetus 29

30 Campylobacter Jejuni Enteritis Important cause of bacterial gastroenteritis Transmitted by beverages and food Reach mucosa at the last segment of small intestine near colon; adhere, burrow through mucus and multiply Heat-labile enterotoxin CJT stimulates a secretory diarrhea like that of cholera Symptoms of headache, fever, abdominal pain, bloody or watery diarrhea Treatment with rehydration and electrolyte balance therapy 30

31 Campylobacter fetus opportunistic pathogen that infects debilitated persons or women late in pregnancy Meningitis, pneumonia, arthritis, septicemia in the newborn 31

32 Helicobacter Pylori: Gastric Pathogen Curved cells discovered in 1979 in stomach biopsied specimens Causes 90% of stomach and duodenal ulcers; apparent cofactor in stomach cancer People with type O blood have a 1.5-2X higher rate of ulcers Produces urease which converts urea into ammonium and bicarbonate 32

33 Figure The causative agent of stomach ulcers 33

34 21.3 Medically Important Bacteria of Unique Morphology and Biology 34

35 Family Rickettsiaceae Contains about 23 species of pathogens, mainly in the genus Rickettsia Cause diseases called rickettsioses All are intracellular parasites requiring live cells for cultivation Spend part of their life cycle in arthropod vectors Rickettsioses are important emerging diseases 35

36 Rickettsia Obligate intracellular parasites Gram-negative cell wall Among the smallest bacteria Nonmotile pleomorphic rods or coccobacilli Ticks, fleas, and lice are involved in their life cycle Bacteria enter endothelial cells and cause necrosis of the vascular lining vasculitis, vascular leakage, and thrombosis 36

37 Specific Rickettsioses 1. Epidemic typhus R. prowazekii carried by lice; starts with a high fever, chills, headache, rash; Brill- Zinsser is a chronic, recurrent form 2. Endemic typhus R. typhi, harbored by mice and rats; occurs sporadically in areas of high flea infestation; milder symptoms 3. Rocky Mountain spotted fever R. rickettsii zoonosis carried by dog and wood ticks; most cases in Southeast and on eastern seaboard; distinct spotted rash; may damage heart and CNS 4. Ehrlichia genus contains 2 species of rickettsias; tickborne bacteria cause human monocytic and granulocytic ehrlichiosis 37

38 38

39 Figure Trends in infection for Rocky Mountain spotted fever 39

40 Figure Transmission cycle in Rocky Mountain spotted fever 40

41 Figure Rash in RMSF 41

42 Related to the Rickettsioses Coxiella burnetti Bartonella sp. 42

43 Causes Q fever Intracellular parasite Coxiella Burnetti Produces an unusual resistant spore Harbored by a wide assortment of vertebrates and arthropods Infectious material includes urine, feces, milk, and airborne particles Usually inhaled causing pneumonitis, fever, hepatitis Tetracycline treatment Vaccine available 43

44 Bartonella Species Small gram-negative, fastidious, cultured on blood agar Cause: Trench fever, spread by lice Cat-scratch disease, a lymphatic infection associated with a clawing injury by cats Bacillary angiomatosus in AIDS patients Tetracycline, erythromycin, and rifampin 44

45 Figure Cat-scratch disease 45

46 The Chlamydiaceae Obligate intracellular parasites Small, gram-negative cell wall Alternate between 2 stages: Elementary body small metabolically inactive, extracellular, infectious form released by the infected host Reticulate body noninfectious, actively dividing form, grows within host cell vacuoles 46

47 Figure Life cycle of Chlamydia 47

48 Chlamydia Trachomatis Human reservoir 2 strains Trachoma attacks the mucous membranes of the eyes, genitourinary tract, and lungs Ocular trachoma severe infection, deforms eyelid and cornea, may cause blindness Inclusion conjunctivitis occurs as baby passes through birth canal; prevented by prophylaxis STD second most prevalent STD; urethritis, cervicitis, salpingitis (PID), infertility, scarring Lymphogranuloma venereum disfiguring disease of the external genitalia and pelvic lymphatics 48

49 Figure The pathology of primary ocular chlamydial infection 49

50 Figure Diagnosis of chlamydial infection 50

51 Chlamydophila A New Genus Contains members that used to be members of genus Chlamydia Chlamydophila pneumoniae causes an atypical pneumonia that is serious in asthma patients 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 51

52 21.4 Molliculites and Other Cell- Wall-Deficient Bacteria Called mycoplasmas Naturally lack cell walls, highly pleomorphic Require special lipids from host membranes Treated with tetracycline, erthyromycin M. pneumoniae primary atypical pneumonia; pathogen slowly spreads over interior respiratory surfaces, causing fever, chest pain, and sore throat M. genitalium and Ureplasma urealyticum weak sexually transmitted pathogens 52

53 Figure The morphology of mycoplasmas 53

54 Bacteria That Have Lost Their Cell Walls Exposure to certain drugs or enzymes can result in cell wall-deficient bacteria called L forms or L-phase Induced or occur spontaneously May be involved in some chronic diseases L- phase variants of group A streptococci, Proteus, and Corynebacterium, Mycobacterium avium paratuberculosis 54

55 21.5 Bacteria in Dental Disease Oral cavity is a complex, dynamic ecosystem, containing 400 species Dental caries slow progressive infection of irregular areas of enamel surface 1. Begins with colonization by slime-forming species of Streptococcus and cross adherence with Actinomyces 2. Process forms layer of thick, adherent material (plaque) that harbors masses of bacteria which produce acid that dissolves enamel 55

56 3. If plaque is allowed to stay, secondary invaders appear Lactobacillus, Bacteroides, Fusobacterium, Porphyromonas, Treponema 4. Acid dissolves tooth enamel leading to caries and tooth damage 56

57 Figure The anatomy of a tooth 57

58 Figure Events leading to dental caries, periodontal disease, and bone loss 58

59 Figure Stages in the formation of plaque and dental caries 59

60 Periodontal Disease Soft tissue disease When plaque becomes calcified into calculus above and below the gingiva This irritates tender gingiva causing inflammation Gingivitis Pockets between tooth and gingiva are invaded by bacteria (spirochetes and gram-negative bacilli) Tooth socket may be involved (peridontitis) Tooth may be lost 60

61 Plaque and Calculus 61

62 Figure Stages in soft-tissue infection, gingivitis, and periodontitis 62

63 Figure Exudate from a gingival pocket 63