Mycoplasma, Spirochetes, Chlamydia, and Rickettsia II Flashcards by Joel Glotfelty

Relapsing fever often described as epidemicor endemic

Borrelia recurrentis

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Organism released only after crushing the lice; not transmitted in saliva, excrement or transovarially

Borrelia recurrentis

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Transmitted by bites from infected ticks(different than those causing Lyme disease); infected ticks are healthy and transmit transovarially

Endemic relapsing fever (Borrelia recurrentis)

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Serve as a reservoir for borella recurrentis

Rodents and small animals

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Occurs in certain arthropod vectors as they transmit disease-causing pathogens from parent arthropod to offspring arthropod

Transovarial transmission

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Sudden onset of fever with chills, severe headache and malaise lasting 3-6 days and ending abruptly

Relapsing fever

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The relapse in relapsing fever occurs

7-10 days later

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The severity of symptoms and duration of illness progressively decrease with each

Relapse

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Usually associated with a single relapse

Louse-borne relapsing fever

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Primarily a disease of wild and domestic animals, human infection through direct or indirect contact with animals

Leptospira

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What is the source of infection with leptospira in descending order?

Dogs, livestock, rodents

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Chronic renal infection in animals may be asymptomatic leading to continuous shedding of the organism in the urine

Leptospira

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Human infection usually indirect, from ingestion of contaminated water or food, or swimming or bathing in contaminated water

Leptospira

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Leptospira are viable in water for

Several weeks

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Likely very under-reported; may be a prominent zoonosis, especially in tropical regions

Leptospira

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Both primary and secondary lesions rich in spirochetes and highly infectious

Treponema pallidium

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Most often transmitted by sexual intercourse, but can be transmitted through the placenta or during birth, by kissing, by transfusion of fresh human blood, other sexual contact or by accidental direct inoculation

Treponema pallidum

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Can invade virtually any organ in the body and the CNS

Treponema pallidum

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Can have active lesions on fingers, breasts, lips, oral cavity or genitals

People infected with syphilis

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Heals spontaneously. 30% of infected are completely cured without treatment

Primary stage of syphilus

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The secondary stage of syphilis is the disseminated stage where we can see secondary lesions

Anywhere on the body

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Serologic tests positive, but no clinical manifestations; 30% stay at this stage if untreated, however blood remains infectious

Latent stage of syphilis

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Slow progressing and we can see inflammatory disease affecting any organ in the body

Late (tertiary) stage of syphilis

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Symptoms range from subacute meningitis to mental deterioration

Neurosyphilis

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Cardiovascular syphilis leads to necrosis of the

Aorta

Lesions in skin (painless) and bone (deep, gnawing pain)

Gummatous syphilis

May result in fetal death and resulting miscarriage, or stillborn at term; signs of congenital syphilis may appear in childhood as developmental abnormalities

Congenital syphilis

What are some of the signs of congenital syphilus?

Notched teeth, saber shins, and saddle nose

Because live bacteria are present in primary and secondary syphilis--ANY physical contact-either sexual, or nonsexual, can

Spread the infection

Can be quickly and directly detected upon examination of exudate from primary, secondary and congenital lesions by dark-field microscopy

T. pallidum

Measure either nonspecific nontreponemal or specific antitreponemal antibodies

Serological tests for T. pallidum

Rely on the fortuitous observation that Ab's to a lipoidal antigen present in a wide array of host tissues are specifically generated upon syphilis infection

Nontreponemal Tests

These antibodies are referred to as

Reagin

Utilize cardiolipin extracted from mammalian tissue (e.g. beef heart) as the Ag

Nontreponemal Tests

Then addition of lecithin and cholesterol sensitizes the cardiolipin to react with syphilitic reagin, resulting in

Flocculation

What are the two types of tests to measure the presence of reagin?

Flocculation tests and Complement fixation

Reagin in serum can fix complement in the presence of

Cardiolipin

Unfortunately though, generation of reagin antibodies occur in

Other infections

Patients with progressive tertiary syphilis may spontaneously become negative using

Nontreponemal tests

Detect T. pallidum antibodies in patient serum

Specific treponemal tests

Once treponemal Abs are generated, they remain for

A lifetime

What percentage of patients with primary syphilis will be true positives?

60-85%

Which percentage of secondary and tertiary syphilis patients will be truly positive?

100%

What are two examples of common treponemal Ab tests?

1. ) FTA-ABS | 2. ) TPHA

Indirect immunofluorescence; rabbit T. pallidumas Ag, test for Ab in serum

FTA-ABS (Fluorescent Treponemal Ab)

RBCs treated to adsorb T. pallidum on surface, RBCs then clump when mixed with antitreponemalantibodies

TPHA (T. pallidum hemagglutination)

What are the two major groups of Rickettsia and Orientia?

1. ) Spotted fever group | 2. ) Typhus group

What are the two components of the spotted fever group?

Rickettsia rickettsii and rickettsia akari

What are the three components of the typhus group?

Rickettsia prowazekii, Rickettsia typhi, and Orientia tsutsugamushi

Severity of diseases these organisms cause is variable depending on the organism and host factors -All are obligate intracellular organisms

Erlichia, anaplasma, and Coxiella

All organisms except Coxiellaare transmitted to humans by

Arthropod vectors such as fleas, lice, mites, and ticks

A zoonosisin which sheep, goats and cattle constitute the primary reservoirs that shed the organism in urine, feces, birth products and milk

Coxiella Burnetii

Targets columnar epithelial cells that line mucous membranes; correlates well with infections it causes (conjunctivitis, cervicitis, pneumonia)

Chlamydia

Most target endothelial cells that line blood vessels; vascular lesions throughout body produce systemic manifestations and hallmark rash

Rickettsia

The seasonal and geographical distribution of the diseases caused by these organisms is dependent on the habitat of the

Vector

Tick behavior also influences seasonality, clinical presentation and age of human population targeted for tick-borne diseases caused by

Rickettsia rickettsii, Ehrlichia and Anaplasma

In most cases, humans are incidental hosts and do not help propagate the

Organism

The exception to this rule is -causes louse-borne typhus

Rickettsia prowazekii

Common symptoms of infection in both are fever, headacheand rash

Rickettsia and orientia

Highly adapted for intracellular survival

Rickettsia

Have undergone genomic reduction by relying on their host to provide many essential amino acids, nucleotides and other nutrients; uses transport system to bring these nutrients into the cell

Rickettsia

More closely related to mitochondria than other bacteria

Rickettsia

most virulent of the group, ~5% fatality rate (~25% in the preantibioticera)

Rickettsia rickettsii

Rickettsia rickettsii causes

Rocky mountain spotted fever

Early diagnosis is deceptively difficult because hallmark rash appears 2-4 days after onset of illness

Rocky mountain fever

Rickettsia rickettsii attach to receptors on host vascular endothelial cells via the outer membrane proteins

OmpA or OmpB

Escape from phagosome into host cytosol & proliferate

Rickettsia Rickettsii

Proliferation in cytosol leads to cell damage leading to increased vascular permeability

Rickettsia Rickettsii

Rickettsia rickettsii spread to adjacent cells through hoest cell

Actin-mediated propulsion

A manifestation of the networks of contiguously infected cells

The characteristic petechial rash

Dermacentor variabilis, the American dog tick, is the predominant vector in the eastern two thirds of the United States; Dermacentor andersoni, the Rocky Mountain wood tick, is the prevalent vector in the Western states for

Rocky Mountain Spotted Fever

What is the incubation period for Rocky Mountain Spotted Fever (RMSF)?

2-14 days (median of 7 days)

Disease begins with fever, severe headache, myalgia; rash (90% of patients, petechialin ~50% of cases)

RMSF

Occurs 3-5 days after onset of fever, usually begins around wrist and ankles and spreads toward trunk

Rash from RMSF

Rocky Mountain “spotless” fever (10% of cases) is documented mostly in

Older or black patients

Transmitted to humans through a mouse mite (small and colorless; bite is painless); however seroprevalence high in NYC dogs so another vector suspected

Rickettsialpox

Rickettsialpox is caused by

Rickettsia akari

What are the target cells of Rickettsia akari?

Macrophages/monocytes

Characterized by a primary papule, which ulcerates and forms the dark eschar (clinical hallmark -present 100% of the time) -At the site of the tickbite

Rickettsialpox

Only Rickettsia that is capable of causing devastating epidemics

Rickettsia prowazekii

Rickettsia prowazekii causes

Louse-borne typhus

Transmitted by close person-to-person contact by the body louse

Louse-borne typhus

The body louse is strictly adapted to humans; it lives in clothes and takes a blood meal

5 times/day

Recently, flying squirrels in the US shown to be stable reservoirs for

R. prowazekii

Now categorized as an agent for bioterrorism (Category B) because it can be aerosol-transmitted and weaponized

R. prowazekii

Severe headache, fever, myalgia and rash that spreads from trunk to extremities (opposite RMSF) is characteristic of

Louse-borne typhus

The louse-borne typhus rash spares the

Face, palms, and soles

The primary illness from R. prowazekii is louse-borne typhus. The recrudescent form is

Brill-Zinsser disease

Thought to arise from stress or from a compromised immune system

Brill-Zinsser disease

Systematic endothelial infection with symptoms similar to RMSF and louse-borne typhis, but usually milder

Murine typhus

Murine typhus is caused by

Rickettsia Typhi

Nearly all cases of murine typhus present with

Fever

Scrub typhus is transmitted transovarally, favoring females. It is caused by

Orientia tsutsugamushi

Unlike most rickettsia, infection does not occur through endothelial cells

Ehrlichia and anaplasma

Infects monocytes and macrophages

Ehrlichia

Infects neutrophils

Anaplasma

Multipy within cytoplasmic membrane-bound vesicles that look like inclusion bodies but are referred to as morula

Ehrlichia and anaplasma

Cell walls are thin because they lack peptidoglycan and LPS

Ehrlichia and anaplasma

Majority of cases in May-August in south-central and southeastern US, i.e. the habitat of the lone star tick, the dog tick, and Ixodes pacificus

Human Monocyte Ehrlichiosis (HME)

Human Monocyte Ehrlichiosis (HME) is caused by

Ehrlichia chaffeensis