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Foundations in
Microbiology
Seventh Edition
Talaro
Chapter 21
Miscellaneous Bacterial
Agents of Disease
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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
2
Figure 21.1 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
• Human is 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
7
8
Figure 21.3 Primary syphilis lesion,
chancre
9
Figure 21.4 Symptom of
secondary syphilis
10
Figure 21.5 and 21.6
Manifestations of syphilis
11
Figure 21.7 Congenital syphilis
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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
13
Figure 21.8 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
Figure 21.9
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
Figure 21.10 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
Figure 21.11 Cycle of Lyme disease
22
Figure 21.12 Views of Lyme disease
skin rash
23
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
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
Figure 21.14 (a-b) Alterations in intestinal
function caused by cholera toxin
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Figure 21.14 (c)
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
Figure 21.16 The causative agent of
stomach ulcers
33
21.3 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
1. Epidemic typhus – R. prowazekii carried by lice;
starts with a high fever, chills, headache, rash; BrillZinsser 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
Figure 21.18 Trends in infection for
Rocky Mountain spotted fever
39
Figure 21.19 Transmission cycle in
Rocky Mountain spotted fever
40
Figure 21.20 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
Figure 21.22 Cat-scratch disease
45
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
Figure 21.23
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
Figure 21.24 The pathology of primary
ocular chlamydial infection
49
Figure 21.26 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
51
21.4 Molliculites and Other CellWall-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
Figure 21.27
The morphology
of mycoplasmas
53
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
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
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
Figure 21.28
The anatomy of a tooth
57
Figure 21.29
Events leading
to dental caries,
periodontal
disease, and
bone loss
58
Figure 21.30 Stages in the formation of plaque and dental caries 59
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
Plaque and Calculus
61
Figure 21.33 Stages in soft-tissue infection,
gingivitis, and periodontitis
62
Figure 21.34
Exudate from a gingival pocket
63