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The Spirochetes. Gram-negative human pathogens Free living saprobes, or commensals of animals, not primary pathogens Treponema Leptospira Borrelia. Typical spirochete. Genus Treponema. Thin, regular, coiled cells

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the spirochetes
The Spirochetes
  • Gram-negative human pathogens
  • Free living saprobes, or commensals of animals, not primary pathogens
    • Treponema
    • Leptospira
    • Borrelia
genus treponema
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
treponema pallidum the spirochete of syphilis
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
pathogenesis and host response
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
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
diagnosis and treatment
Diagnosis and Treatment
  • Stages of syphilis mimic other diseases
  • Consider symptoms, history, microscopic, and serological testing
  • Treatment: penicillin G
nonsyphilitic treponematoses
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
leptospira and leptospirosis
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.
borrelia arthropod borne spirochetes
Borrelia: Arthropod-Borne Spirochetes
  • Large, 3-10 coils irregularly spaced
  • Borrelioses transmitted by arthropod vector
  • B. hermsii – relapsing fever
  • B. burgdorferi – Lyme disease
b hermsii relapsing fever
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
b burgdorferi lyme disease
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
curviform gram negative bacteria and enteric diseases
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
vibrio cholera
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
pathogens carried by seafood
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
diseases of the campylobacter vibrios
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
campylobacter jejuni enteritis
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
Campylobacter fetus – opportunistic pathogen that infects debilitated persons or women late in pregnancy
  • Meningitis, pneumonia, arthritis, septicemia in the newborn
helicobacter pylori gastric pathogen
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
family rickettsiaceae
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
  • 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
specific rickettsioses
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
related to the rickettsioses
Related to the Rickettsioses
  • Coxiella burnetti
  • Bartonella sp.
coxiella burnetti
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
bartonella species
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
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
chlamydia trachomatis
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
chlamydophila a new genus
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
molliculites and other cell wall deficient bacteria
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
bacteria that have lost their cell walls
Bacteria That Have Lost Their Cell Walls
  • Exposure to certain drugs or enzymes can result in cell wall-deficient bacteria called L forms or


  • Induced or occur spontaneously
  • May be involved in some chronic diseases
    • L- phase variants of group A streptococci, Proteus, and Corynebacterium, Mycobacterium avium paratuberculosis