The Spirochetes

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

2. Typical spirochete

3. 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. Treponema Pallidum: The Spirochete of Syphilis • Humans are the natural host • Extremely fastidious and sensitive; cannot survive long outside of the host • Sexually transmitted and transplacental

5. 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. 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

8. Primary syphilis lesion, chancre

9. Symptom of secondary syphilis

10. Manifestations of syphilis

11. Congenital syphilis

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

13. Treponema pallidum

14. 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. Endemic treponematoses

16. 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 • 50-60 cases a year in U.S.

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

18. 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. Pattern in relapsing fever

20. 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. Cycle of Lyme disease

22. Views of Lyme disease skin rash

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

24. Vibrio Cholera • Comma-shaped, possess unique O and H Ags • El Tor biotype: survives longer, more infectious • Infectious dose 108 • 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. Alterations in intestinal function caused by cholera toxin

26. Alterations in intestinal function caused by cholera toxin

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

31. 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. The causative agent of stomach ulcers

33. Medically Important Bacteria of Unique Morphology and Biology

34. 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. 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. Specific Rickettsioses • Epidemic typhus – R. prowazekii carried by lice; starts with a high fever, chills, headache, rash; Brill-Zinsser is a chronic, recurrent form • Endemic typhus – R. typhi, harbored by mice and rats; occurs sporadically in areas of high flea infestation; milder symptoms • 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 • Ehrlichia genus contains 2 species of rickettsias; tick-borne bacteria cause human monocytic and granulocytic ehrlichiosis

38. Trends in infection for Rocky Mountain spotted fever

39. Transmission cycle in Rocky Mountain spotted fever

40. Rash in RMSF

41. Related to the Rickettsioses • Coxiella burnetti • Bartonella sp.

42. Coxiella Burnetti • Causes Q fever • Intracellular parasite • 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. 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. Cat-scratch disease

45. TheChlamydiaceae • 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. Life cycle of Chlamydia

47. 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. The pathology of primary ocular chlamydial infection

49. Diagnosis of chlamydial infection

50. 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