MEDS 2014 – BUG WEEK HANDOUT (SPIROCHAETES) – While sometimes described as “Gram-negative-like”, the spirochaetes differ enough from both
gram-negative and gram-positive organisms to form their own phylum (technical term essentially meaning “division”) within the larger taxonomic rank that all
bacteria are classified under. Spirochaetes have both inner and outer membranes separated by a periplasmic space. They are characterized by their spiral
shapes and intramembranous flagella, the latter of which provides motility. The spirochaetes are too narrow (0.1 – 0.2 µm) to be seen by conventional stains and
light microscopy, but can be visualized by dark field microscopy, fluorescence microscopy and some specialized stains. Spirochaetal diseases include:
Spirochaetal disease Basic characteristics
and appearance
1 – Syphilis
Tightly wound spiral
(Treponema pallidum lends unique rotary
pallidum)
motion
Smooth outer surface
due to a relative lack
of membrane proteins
Small bacterial
genome
2 – Leptospirosis
‘End-hook’ is unique—
(Leptospira
allows better
interrogans)
attachment to host;
needs long chain fatty
acids to survive
General environment
Found as natural
pathogen within
humans and certain
monkeys and higher
apes; an obligate
parasite
Mode of
transmission
Sexual intercourse,
oral sex, kissing
(via exposure to
active lesions)
Vertical
transmission
(mother to child)
Pathophysiology and natural history
Incubation averages 21 d
1º syphilis: chancre at site of inoculation
2º syphilis: systemic symptoms (diffuse
rash, including palms/soles; malaise,
fever); development of condyloma lata
Late syphilis: variable presentation; can
involve cardiovascular and central
nervous systems
Tropical and more
From infected
Incubation averages of 10 d
temperate regions
animals to humans Non-specific constitutional symptoms
Likes the kidney tubules or from urineMore specific: Weil’s syndrome,
of many mammals
contaminated
meningitis, pulmonary haemorrhage,
environments to
conjunctival suffusion
humans (NOT
human-to-human)
3 – Lyme disease
Most common tickWooded areas across
Uses tick as vector Incubation averages 7-10 d
(Borrelia burgdoferi in borne infection in
the Northeast and
for transmission
Formation of red rash (erythema migrans)
N. America; has
North America
Central states; present
Mild constitutional symptoms
European and Asian
in Canada
Later stages: chronic arthritis (potentially
cousins)
deforming) and CNS effects possible
Western USA: B.
4 – Relapsing fever (in Looser spiral
Ticks and lice used Incubation averages 3-12 d
hermsii, B. turicatae
North America:
as vector for
High fever (up to 43ºC) for a couple days
Borrelia hermsii,
(found in ticks), rustic
transmission
followed by hypotension and drop in temp
Borrelia turicatae and
cabins, wooded areas
Evasion of immune system
Borrelia reccurentis)
Africa: B. reccurentis
(rearrangement of variable membrane
(found in lice), poor
proteins) causes cycles of fever and relief
sanitation
5 – Yaws (Treponema High lipid content
Tropical areas of Africa, Direct person-to1º stage: lesion at inoculation site after 3
pallidum pertenue)
Relies on host for fatty Asia, S. America
person contact
wk incubation
acids, nucleotides and Optimal conditions: pH (through break in
2º stage: widespread dissemination
amino acids
7.2-7.4; 30-37ºC
the skin); children through blood results in multiple skin
Microaerophilic (require under 15 more
lesions
O2, but at lower
likely to be affected Latent stage: symptoms usually absent
concentration that that
for up to 5 y; relapse may occur
present in atmosphere)
3º: bone, joint and soft tissue lesions and
deformities may occur
Diagnosis
Difficult to grow in
culture—clinical
features important
1º syphilis: can identify
by dark field microscopy
Later: serological
testing on at risk
populations
Clinical features
combined with history
Retrospective
confirmation by four-fold
rise in agglutinating Ab
titer
Erythema migrans
diagnostic in endemic
area
Ab test available
Travel history to
endemic regions
Peripheral blood smear
with Gemsa or Wright
staining to confirm
diagnosis
Clinical features are
fairly characteristic
(especially in a child
with appropriate travel
history); serologic and
microscopy tests
available to confirm
diagnosis