Download Lecture 12

PCMS 2007
DR JEANNETTE WADULA
Consultant Microbiologist
CMID/NHLS
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SPIROCHETES
SPIROCHETES
OBJECTIVES
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Describe the characteristics and classification of
Spirochetes
Discuss the etiology and epidemiology of
spirochetal diseases
Identify the pathogenic and clinical similarities of
spirochetes
Discuss briefly the principles of diagnosis and
management
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Characteristics of Spirochetes
Spirochetes are unusual gram-negative,
helically curved bacteria with a complex
peptidoglycan-cytoplasmic
membrane,referred to as protoplasmic
cylinder surrounded by an outer
membrane(lipid bilayer sheath)
 Free-living or host associated (colonize)
bacteria widespread in nature
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Their motility differs from other bacteria
owing to the unique structure
(presence of periplasmic flagella
within the periplasma)
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Periplasmic fibrils, are responsible for their
cockscrew movement
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CLASSIFICATION
Class Spirochaetes
Order spirochetales
Leptospiraceae
Leptospira (Zoonosis)
Spirochaetaceae
Treponema (human-human contact)
Borrelia (Zoonosis)
Other
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Of the six genera, three- Treponema, Borrelia
and Leptospira
contain organisms pathogenic for
humans
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Human Spirochetal diseases and
their etiologic agents
Infecting organism
Treponema
 T. carateum
 T. pallidum subspecies
pertenue
 T. pallidum subspecies
endemicum
 T. pallidum subspecies
pallidum
Disease
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Pinta
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Yaws
Bejel, Endemic
syphilis
Syphilis
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Human spirochetal diseases and
their etiologic agents
Leptospira interogans
Leptospirosis
Borrelia spp (
recurrentis, hermsii,
turicatae)
Relapsing fevers
(epidemic or)
sporadic
Borrelia burgdoferi
Lyme disease
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Epidemiology
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Treponemes- except for
congenital syphilis
(transplacental), syphilis is
transmitted through sexual
contact
Pinta, Yaws and endemic
syphilis – nonvenereal
trepomatoses are not spread by
sexual contact but by
close skin-skin contact
between humans and there
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is no known animal
reservoir.
Leptospira and Borrelia
are zoonotic i.e., animal
reservoirs exist and infect
humans via direct or
indirect contact.
Human leptospirosis is
acquired by direct contact
with contaminated urine
from rats, pigs, dogs,
cats...
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Epidemiology
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Many animals are
asymptomatic carriers of
L. interrogans in their
kidneys –no arthropod or
insect vector
Relapsing fever is
transmitted by either
infected human
louse(LBRF)/tick(TBRF)
(B. recurrentis- transovarial
passage doesn’t occur ) by
bites-epidemic form
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Ticks (ornithodoros) are
vectors of sporadic cases
of relapsing fever
These infected ticks
transmit infection
transovarily for
generations and remain
infective for many years
without feeding
Lyme disease is
transmitted to humans by
a minute tick (ixodes)
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Pathogenic features
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Spirochetes invade
host tissue at mucus or
skin membranes
(portal of entry), cause
infection and gain
access to the lymph
systems and blood
Spirochetemia early in
the course,  wide
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dissemination
throughout tissues,
and body fluids, 
one/more stages of
disease, often
intervening latent
periods (1o2o3o)
Such illness suggests
that pathogenic
spirochetes
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Pathogenic features
share unique virulence characteristics
 Once pathogen has entered host, it is
successful at evading defense mechanisms
by not being immunogenic
 In most cases, spirochetes persist in host for
extended periods, late presentation of
disease appears to be due to the presence of
viable organisms
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Clinical similarities
common tropism for the skin, bone, and
central nervous system
 Myocardial disease is found in
leptospirosis, relapsing fever, possibly
syphilis and Lyme disease
 Chronic arthritis uniquely occurs in Lyme
disease, but can occur in syphilis also
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Principles of diagnosis and
management
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Based on recognition of
clinical features of patient
illness with a history of
possible exposure to the
causative organism
Based on either direct
detection (dark-field
microscopy /culture) or
serology(IFA/ELISA).
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Treponema spp have not
been cultured, do not take
up aniline stains gram
stain not effective. Dark
field illumination allows
visualisation,
nontreponemal (RPR,
VDRL-) and treponemal
tests (fluorescently labeled
antibody..) can be used
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Principles of diagnosis and
management
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L.interrogans can be
grown on artificial culture
media can be isolated
from patients blood.
Serologic diagnosis is
made using convalescent
serum
Borrelia relapsing fevers –
blood smears with typical
spirochetes, blood cultures
possible but serologic
diagnosis difficult
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Borreliae stain well with
aniline dyes and can be
observed with the ordinary
light microscope!!!
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Lyme disease – culture of
B. burgdoferi from
patients blood is definitive
but rare except from skin
biopsy samples.
Determination of specific
antibody titers – most
helpful
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References
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Manual of Clinical Microbiology seventh
edition, Murray.
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Frambesia- T. pertenue
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Bone disfiguration-tertiary T. pertenue infection
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