Foundations in Microbiology - LTCC Online · Chapter 21 Miscellaneous Bacterial ... Zinsser is a...
Transcript of Foundations in Microbiology - LTCC Online · Chapter 21 Miscellaneous Bacterial ... Zinsser is a...
Foundations in
Microbiology Seventh Edition
Chapter 21
Miscellaneous Bacterial
Agents of Disease
Lecture PowerPoint to accompany
Talaro
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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21.1 The Spirochetes
• Gram-negative human pathogens
• Free living saprobes, or commensals of
animals, not primary pathogens
– Treponema
– Leptospira
– Borrelia
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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
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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
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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
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• 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
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Diagnosis and Treatment
• Stages of syphilis mimic other diseases
• Consider symptoms, history, microscopic,
and serological testing
– RPR, VDRL, FTA-ABS
• Treatment: penicillin G
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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
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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.
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Borrelia: Arthropod-Borne
Spirochetes
• Large, 3-10 coils irregularly spaced
• Borrelioses transmitted by arthropod vector
• B. hermsii – relapsing fever
• B. burgdorferi – Lyme disease
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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
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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
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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
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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
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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
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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
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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
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• Campylobacter fetus – opportunistic
pathogen that infects debilitated persons or
women late in pregnancy
• Meningitis, pneumonia, arthritis, septicemia
in the newborn
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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
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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
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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
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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; tick-borne bacteria cause human monocytic and granulocytic ehrlichiosis
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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