Chapter 21 – Chlamydia, Mycoplasma, & Ureaplasma Species

MLAB 2434 – Clinical MicrobiologyCecile 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)

Life Cycle of Chlamydia

EB infects host cell by inducing energy-requiring 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

Chlamydia pneumoniae (cont’d) 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 fluorescein-conjugated antibodies

Serologic tests are method of choice for detection (Four-fold rise in titer)

Chlamydia trachomatis

Most commonly sexually transmitted bacterial pathogen in U.S.Only HPV is a more commonly

sexually transmitted diseaseAdult males

• Non-gonococcal urethritis (NGU)• Epididymitis and prostatitis

Chlamydia trachomatis (cont’d)

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

Chlamydia trachomatis (cont’d) 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

Chlamydia trachomatis (cont’d) Laboratory Diagnosis

Direct microscopic examination to find EBs (p. 646)

Cell cultureEnzyme immunoassayNucleic 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

Mycoplasma and Ureaplasma Species General Characteristics

Once thought to be viruses because of size

Mycoplasmas are the smallest free-living organism in nature

Three human pathogens• 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-wall-active antibiotics)

Slow growing, highly fastidious, facultative anaerobes

Require complex media for growth

Clinical Infections

Mycoplasma pneumoniae 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

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