Chapter 21 –
Chlamydia,
Mycoplasma, &
Ureaplasma Species
MLAB 2434 – Clinical Microbiology
Cecile Sanders & Keri Brophy-Martinez
Chlamydia Characteristics
Unique growth cycle because they
are deficient in independent
energy metabolism; therefore
they are obligate intracellular
parasites
 Replication involves elementary
body (EB) and reticulate body
(RB)
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Life Cycle of Chlamydia
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EB infects host cell by inducing energyrequiring active phagocytosis
EB organize into large, reticulating initial
bodies, which divert the cells’
synthesizing functions to their own needs
and begin to multiply by binary fission
Organisms begin reorganizing into
infective EBs.
Disrupted host cell dies, releasing new
EBs
Life Cycle of Chlamydia
Chlamydia pneumoniae
Most recognized species of
Chlamydia
 Important respiratory pathogen
(acute respiratory disease,
pneumonia, and pharyngitis)
 Implicated in asthma
 Risk factor for Guillain-Barre’
syndrome
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Chlamydia pneumoniae
(cont’d)
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Common (50% of adults have antibodies)
College age students most susceptible
Reinfection common
Prolonged sore throat and hoarseness,
followed by flu-like lower respiratory
symptoms
Can be following by pneumonia and
bronchitis
Third most common respiratory infection
Chlamydia pneumoniae
(cont’d)
If cultured, must be in cells
(obligate intracellular pathogen) and
then visualized with fluoresceinconjugated antibodies
 Serologic tests are method of
choice for detection (Four-fold rise
in titer)
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Chlamydia trachomatis
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Most commonly sexually
transmitted bacterial pathogen in
U.S.
Only HPV is a more commonly
sexually transmitted disease
 Adult males
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• Non-gonococcal urethritis (NGU)
• Epididymitis and prostatitis
Chlamydia trachomatis
(cont’d)
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Adult females
• Urethritis, follicular cervicitis,
endometritis, proctitis, salpingitis, PID
and perihepatitis (Fitz-Hugh-Curtis
syndrome)
Major cause of sterility in U.S.
 May be transmitted to newborns
during delivery
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Chlamydia trachomatis
(cont’d)
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Other sites of infection
Trachoma – infection of the
conjunctiva, resulting in scarring and
blindness (Mostly in India and
Egypt)
 Lymphogranuloma verereum – STD
found in immigrants
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Chlamydia trachomatis
(cont’d)
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Laboratory Diagnosis
Direct microscopic examination to
find EBs (p. 646)
 Cell culture
 Enzyme immunoassay
 Nucleic acid probes with and
without amplification (PCR)
 Serologic (antibody) assay

Chlamydia psittaci
Causes psittacosis (parrot fever)
 Identification based on history of
close contact with birds and
serologic evaluation
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Mycoplasma and
Ureaplasma Species
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General Characteristics
Once thought to be viruses because
of size
 Mycoplasmas are the smallest freeliving organism in nature
 Three human pathogens
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• Mycoplasma pneumoniae - respiratory
• Mycoplasma hominis - urogenital
• Ureaplasma urealyticum - urogenital
Mycoplasma and Ureaplasma
Species (cont’d)
Pleomorphic organisms – do not have
a cell wall (resistant to cell-wallactive antibiotics)
 Slow growing, highly fastidious,
facultative anaerobes
 Require complex media for growth
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Clinical Infections
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Mycoplasma pneumoniae
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Causes bronchitis, pharyngitis, or primary
atypical pneumonia (a.k.a. “walking
pneumonia”)
Usually infects school-age children and
young adults in close quarters (dorms,
military barracks, etc.)
50% of infections produce “cold
agglutinins”
Most often diagnosed by serologic
evaluation
M. hominis & U.
urealyticum
Most often associated with
urogenital tract infections
 May be isolated from asymptomatic
individuals
 Can be transmitted to the fetus at
delivery
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Laboratory Diagnosis
Cultures must be delivered
immediately to the lab, because the
organisms are very susceptible to
drying
 Should be placed in transport media
 If not plated immediately, should be
frozen at -70°C
 Most infections detected via
serologic evaluation
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