Mycoplasma, Rickettsias,
Chlamydias, Spirochetes, Vibrios
Nestor T. Hilvano, M.D., M.P.H.
Images Copyright by Bauman, Robert. 2009. Microbiology, With
Diseases by Taxonomy, 3rd edition, Pearson Benjamin Cummings
Learning Objectives
1. Discuss the damage done to respiratory epithelial cells by Mycoplasma
pneumoniae.
2. Describe the three species of Rickettsia that are responsible for human
infections.
3. Describe the rash and petechiae of Rocky Mountain spotted fever.
4. Describe Chlamydia including the two cellular forms.
5. Explain how non-sexually active children may become infected with C.
trachomatis .
6. Describe the cause and symptoms of lymphogranuloma venereum.
7. Describe three diseases associated with Chlamydia pneumoniae .
8. Describe the disease caused by Treponema pallidum .
9. Describe Lyme disease, its vector, and its causative agent.
10. Describe the action of cholera toxin in causing cholera.
11. Name two species of Vibrio transmitted via contaminated shellfish and
describe their diseases.
12. Describe gastroenteritis caused by Campylobacter jejuni .
13. Discuss the major change in medical opinion of the cause of peptic
ulcers.
14. Describe the effect of Helicobacter pylori of the lining of the human
stomach.
Mycoplasma
• Smallest, free-living
(0.1 to 0.8 um)
• lack cell wall
• Require growth factors
• Except M. pneumoniae,
all are facultative anaerobes, with fried-egg
shaped colonies seen on agar
• M. genitalium and Ureaplasma urealyticum –
cause nongonococcal urethritis
• M. hominis – cause pyelonephritis, postpartum
fever, PID
Mycoplasma pneumonia
• Primary atypical pneumonia
(walking pneumonia)- mild case,
does not generally require
hospitalization; spread via droplets
• Attaches to receptors in human
respiratory tract; interrupt removal of
mucus
• Common between 5 to 15 yrs.
old and adults younger than 40 ;
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last several weeks
Difficult to diagnose – grow slowly in
culture, 2 to 6 weeks
Rx – erythromycin or tetracycline
Prev – personal hygiene, avoid contact
with fomites, reduced aerosol
dispersion
No vaccine
* Uniform granular
appearance
Rickettsias
• Gm (-), non-motile, aerobic,
intracellular parasites
• R. rickettsii – rocky mountain
spotted fever, prevalent in
Appalachian mountains, Oklahoma,
and southeastern U.S
• Transmitted by arthropod
vectors ticks (genus Dermacentor)
to rabbits/rodents (human incidental
host); 3-12 days incubation period
• S/Sx – fever and spotted,
non-itchy rash on trunk and limbs;
develop petechiae; spread to organs
• Prev = wear close fitting cloths,
use tick repellant, avoid infested areas
• Rx = chloramphenicol, tetracycline
Rickettsias
• R. typhi – cause murine typhus
- fleas are main vectors; endemic in U.S.
- symptoms in 10 days, lasts about 3
weeks, not fatal
- fever, chills, headache, muscle pain, nausea, rash in less
than half of patients
• R. prowazeki – cause epidemic typhus (louse-borne typhus)
- human are primary host; squirrels and their fleas
- dev. recurrence many years later (Brill-Zinsser disease)
- occurs in crowded, unsanitary living conditions; endemic in
central and south america, africa, and eastern U.S.
- fever, physical and mental depression, and rash
- attenuated vaccine for high risk populations
• Dx – S/Sx; serologic tests; fluorescent antibody tests
• Rx – doxycycline, tetracycline, or chloramphenicol
Clamydias
• Nonmotile, grow and
multiply within vesicles
of host cells
• No cell wall
• 2 forms = elementary
bodies (EB), infective
form and can survive
outside cells; and
reticulate bodies (RB),
noninfective
intracellular form
Clamydia trachomatis
• Most common STD in U.S., non-gonococcal
urethritis (NGU)
• Obligate intracellular; 0.2-0.3 um; coccoid
• Pathogenesis
– in man, monkey, and rabbit
- via sexual contact, fomites
- 7 to 10 days incubation period
- painless vesicles on genitals, rupture, heal
* Sequelae:
a. lymphogranuloma venereum (LGV) – enlarge
/harden lymph node, form buboes
(granulomatous nodules), elephantiasis
b. blindness (trachoma) – chlamydia opthalmia
in children at birth
c. PID – in infected women
• Dx – find organism, fluorescent (monoclonal)
antibody test
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Rx – tetracycline, or erythromycin; sulfonamides in pregnant women
Spirochetes: Treponema pallidum
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Gram (-), anaerobe
Spirochetes – helical; endoflagellate
Epidemic in France, 1495
Duplication time = 30 hours; only in man/monkey
Unable to grow in culture; sensitive to drying;
killed at 41.5˚C in 1 hr.
Pathogenesis:
- 1˚ stage = chancre (local response),
10 – 21 days after exposure, remain for 3-6
weeks; hardened and painless
- 2˚ stage = systemic response; 4 -8 weeks
later; rash on skin, mouth, lips, genitalia;
25% cured, 25% remain latent (carriers),
50% go on to 3˚ stage
- 3˚ stage = hyperimmune response;
gumma (painful, rubbery lesion in bones,
nervous tissue, or skin);
can result to dementia, blindness, heart failure,
paralysis (tabes dorsalis or neurosyphilis)- dorsal
column of s.c.
Dx – find organisms; specific antibody test
Rx - penicillin
Vibrio cholera
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Gm (-), curved rod, monotrichous
O polysaccharide antigen, Oxidase (+)
Strain O1 el Tor causes cholera
in areas with poor sewage and
water Rx
Symptoms dev. 2-3 days after infection
Pathogenesis: cholera toxin (exotoxin) activates cAMP
conversion, phosphorylates ionic pumps in intestine, moves
electrolytes from blood into intestinal lumen, prevent Na+
and K+ absorption, results to osmosis, leading to severe
diarrhea
Rice watery stool (mucus + epithelial cells)
Severe dehydration and electrolyte loss
1991-1994 South America, 1 million cases with 10,000
deaths
Rx – fluid and electrolyte replacement; tetracycline
Other Vibrios
• V. parahaemolyticus – cholera-like
gastroenteritis after ingestion of
contaminated shellfish; self limiting
- explosive diarrhea, headache, nausea,
vomiting and cramps for 72 hrs.
• V. vulnificus – septicemia following
consumption of contaminated shellfish,
and wound infection after washing with
contaminated seawater
- fatal in half of untreated cases
Campylobacter jejuni
• Gm (-), microaerophilic, curved
• Optimum temp. 45˚C (105˚F)
• Most frequent cause of diarrhea in U.S. (2 million
cases per yr.)
• From contaminated milk/feces of cattle (60%
cattle are carriers)
• 0.1% dev. Guillain Barre syndrome
- autoimmune disease, demyelination of facial
nerve, usually temporary paralysis of face
• Usually self-limiting (malaise, fever, bloody
diarrhea, may last for 7 – 10 days)
• Prev – proper food handling and cooking
Helicobacter pylori
• Slightly helical, motile with
sheathed flagella
• Most are asymptomatic; some
develop Peptic Ulcer
• Penetrate mucous lining, susceptible
to damage by gastric acids, can 
production of acids
• Urease (+) to neutralize HCL (urea→ ammonia)
• Grow at pH 1 to 3
• Portal of entry – mouth
• Dx – Urease test; blood test (antibodies for H. pylori
exposure); Upper GI X-ray; Endoscopy
• Rx – combination of 2- 3 antibiotics with acid inhibitors
• Borrelia burgdorferi – cause
lyme disease; transmitted to
human by deer ticks; skin rash (15 cm),
migratory polyarthritis, posible
neurological/cardiac abnormalities
• Borrelia recurrentis – cause epidemic
relapsing fever (louse-borne fever); transmitted by
human body louse
• Leptospira interrogans – cause leptospirosis
through contact with urine of infected animals or
contaminated waterways or soil; S/Sx = fever, pain,liver
and kidney dysfunction, usually not fatal; occurs
worldwide
Homework
1.
2.
3.
4.
5.
Define terms – elementary bodies; reticular bodies;
lymphogranuloma venereum; trachoma; gumma; and
tabes dorsalis.
Discuss rocky mountain spotted fever as to agent,
manner of transmission, symptoms, and prevention.
Describe the 3 clinical stages of syphilis.
Identify the causative microorganisms of the following:
walking pneumonia, rocky mountain spotted fever,
epidemic typhus, most common STD (non-gonococcal
urethritis) in U.S., syphilis, rice watery diarrhea, peptic
ulcer, lyme disease, leptospirosis, murine typhus, and
louse-borne fever.
What is the arthropod vector that transmit disease of
Rickettsia rickettsia to human as incidental host?