batterjee medical college. dr. manal el said spirochetes head of medical microbiology department

Batterjee Medical College


Dr. Manal El SaidDr. Manal El Said

Spirochetes

Head of Medical Microbiology Department


Treponema pallidum

Diseases

Characteristics

Syphilis

•Spirochetes.• Not seen on Gram-stained smear because organism is too thin.

•Not cultured in vitro.

Habitat and Transmission•Habitat is the human genital tract.•Transmission is by sexual contact • from mother to fetus across the placenta.


Treponema pallidum

Pathogenesis

• Organism multiplies at site of inoculation and then spreads widely via the bloodstream.

• Many features of syphilis are attributed to blood vessel involvement causing vasculitis.

• Primary (chancre) and secondary lesions heal spontaneously.

• Tertiary lesions consist of gummas (granulomas) in bone, muscle, and skin, aortitis, or central nervous system inflammation.


• In primary syphilis, the Spirochetes multiply at the site of inoculation and a local, nontender ulcer (chancre) usually forms in 2 to 10 weeks. The ulcer heals spontaneously, but Spirochetes spread widely via the bloodstream (bacteremia) to many organs.

• One to three months later, the lesions of secondary syphilis occur & appear as a maculopapular rash, on the palms and soles, or as moist papules on skin and mucous membranes . Moist lesions on the genitals are called condylomata lata. These lesions are rich in Spirochetes and are highly infectious, but they also heal spontaneously. Constitutional symptoms of secondary syphilis include low-grade fever, malaise, anorexia, weight loss, headache, myalgias, and generalized lymphadenopathy. There may be internal organ involvement (meningitis, nephritis, hepatitis, etc).

• Tertiary syphilis may show granulomas (gummas), especially of skin and bones. central nervous system involvement or cardiovascular lesions In tertiary lesions, treponemes are rarely seen.

• T. pallidum also causes congenital syphilis. The organism is transmitted across the placenta, after the third month of pregnancy, and fetal infection can occur. Skin and bone lesions are common, as is hepatosplenomegaly. Unless the disease is treated promptly, stillbirth or multiple fetal abnormalities occur.

Treponema pallidum


Laboratory Diagnosis

Treponema pallidum

•Seen by darkfield microscopy or immunofluorescence.

•Serologic tests important: VDRL (or RPR) is nontreponemal (nonspecific) test used for screening; FTA-ABS is the most widely used specific test for Treponema pallidum.

•Antigen in VDRL is beef heart cardiolipin; antigen in FTA-ABS is killed T. pallidum.

•VDRL declines with treatment, whereas FTA-ABS remains positive for life.


Treatment

Treponema pallidum

Prevention

• Penicillin is effective in the treatment of all stages of syphilis.

• In primary & secondary syphilis, use benzathine penicillin G because T. pallidum grows slowly, so drug must be present for a long time.

• There is no resistance.

• Benzathine penicillin given to contacts.• No vaccine is available.


Borrelia burgdorferi

Diseases

Characteristics

Lyme disease

•Spirochetes.

•Gram stain not useful.

•Can be cultured in vitro, but not usually done.



Habitat and Transmission

•The main reservoir is the white-footed mouse.

•Transmitted by the bite of ixodid ticks

•Very small nymph stage of ixodid tick (deer tick) is

most common vector.

•Tick must feed for at least 24 hours to deliver an

infectious dose of B. burgdorferi.

ixodes tick


Pathogenesis

•Organism invades skin, causing

a rash called erythema migrans.

• It then spreads via the

bloodstream to involve

primarily the heart, joints, and

central nervous system.


characteristic red, ring shaped skin lesion with central clearing that first appears at site of tick bite




•Diagnosis made serologically, i.e., by detecting IgM

antibody.

•Confirm positive test with Western blot assay.


Treatment

Prevention

Doxycycline for early stages; penicillin G for late

stages.

•Avoid tick bite. •Can give doxycycline or amoxicillin to people who are bitten by a tick in endemic areas.



•Causes relapsing fever.

•Transmitted by human body louse.

• It has rapid antigenic changes, which account for

the relapsing nature of disease.

• It is due to programmed rearrangements of

bacterial DNA encoding surface proteins.

Borrelia recurrentis


Leptospira interrogans

Diseases

Characteristics


Leptospirosis

•Spirochetes that can be seen on darkfield microscopy but not light microscopy.

• Can be cultured in vitro.

• Habitat is wild and domestic animals. • Transmission is via animal urine. • In the United States, transmission is via dog,

livestock and rat urine.



Pathogenesis• Two phases: - initial bacteremic phase -subsequent immunopathologic phase with

meningitis.




•Darkfield microscopy and culture in vitro are

available but not usually done.

•Diagnosis usually made by serologic testing for

antibodies in patient's serum.


Treatment


Prevention

•Penicillin G.

•There is no significant antibiotic resistance.

• Doxycycline effective for short-term exposure.

• Vaccination of domestic livestock and pets.

• Rat control.



Rickettsiae



Rickettsia rickettsii

Diseases

Rocky Mountain spotted fever

• Fever, severe headache, myalgias, & prostration. • Typical rash, which appears 2 to 6 days later, begins with

macules that progress to petechiae. • Rash appears first on hands & feet & then moves inward to

trunk. • In addition to headache, other profound central nervous

system changes such as delirium & coma can occur.• Disseminated intravascular coagulation, edema &

circulatory collapse may ensue in severe cases.



Characteristics

• Obligate intracellular parasites.

• Not seen well on Gram-stained smear.

• Antigens cross-react with OX strains of Proteus vulgaris

(Weil-Felix reaction).




Pathogenesis

• Dermacentor (dog) ticks are both vector &

main reservoir.

• Transmission is via tick bite.

• Dogs & rodents can be reservoirs.

• Organism invades endothelial lining of capillaries, causing

vasculitis.

• No toxins or virulence factors identified.

ixodes tick




• Detecting antibody in serologic tests such as the ELISA test.

• Weil-Felix test is no longer used. • Stain and culture rarely done.

• Protective clothing & prompt removal of ticks.• Tetracycline effective in exposed persons. • No vaccine is available

TreatmentTetracycline.

Prevention


Rickettsia prowazekii

DiseasesLouse-borne epidemic typhus

• Typhus begins with sudden onset of chills, fever, headache, and other influenzalike symptoms

• Maculopapular rash begins on trunk & spreads peripherally.• Rash becomes petechial & spreads over entire body but

spares face, palms, & soles. • Signs of severe meningoencephalitis, including delirium &

coma • In untreated cases, death occurs from peripheral vascular

collapse or from bacterial pneumonia.



Characteristics

Same as R. rickettsii.

• Humans are the reservoir, and transmission is via

the bite of the human body louse.




PathogenesisNo toxins or virulence factors known.

Serologic tests for antibody in patient's serum.


Treatment

A tetracycline, such as doxycycline.

Prevention•A killed vaccine is used in the military but is not available for civilian use.



Coxiella burnetii



Coxiella burnetii

Diseases

Q fever.

• Main organ involved in Q fever is lungs. • It begins suddenly with fever, severe headache, cough, and

other influenzalike symptoms. • Hepatitis is frequent enough that combination of pneumonia

& hepatitis should suggest Q fever.• Rash is rare• Q fever is acute disease &recovery is expected even in

absence of antibiotic therapy.• Chronic Q fever characterized by life-threatening

endocarditis occurs.


Coxiella burnetii

Characteristics

• Obligate intracellular parasites.• Not seen well on Gram-stained smear.


• Habitat is domestic livestock. • Transmission is by inhalation of aerosols of urine,

feces, amniotic fluid, or placental tissue. • The only rickettsia not transmitted to humans by

an arthropod.


Coxiella burnetii

Pathogenesis

No toxins or virulence factors known.

• Diagnosis usually made by serologic tests. • Weil-Felix test is negative.• Stain and culture rarely done.


Tetracycline.

Treatment

Prevention•Killed vaccine for persons in high-risk occupations



Mycoplasmas



Mycoplasma pneumoniae

Diseases

Characteristics

"Atypical" pneumonia.

•Smallest free-living organisms. •Not seen on Gram-stained smear because they have no cell wall, so dyes are not retained.

•The only bacteria with cholesterol in cell membrane.

•Can be cultured in vitro.




• Habitat is the human respiratory tract.

•Transmission is via respiratory droplets.

Pathogenesis

• No endotoxin because there is no cell wall.

• Produces hydrogen peroxide, which may damage

the respiratory tract.




• Gram stain not useful.

• Can be cultured on special bacteriologic media but

takes at least 10 days to grow, which is too long to

be clinically useful.

• Positive cold-agglutinin test is presumptive

evidence.

• Complement fixation test for antibodies to

Mycoplasma pneumoniae is more specific.


Treatment


Prevention

Erythromycin or tetracycline.

No vaccine or drug is available

batterjee medical college. dr. manal el said spirochetes head of medical microbiology department

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