C h a p t e r 4 1
Sexually Transmitted Infections
1057
is metabolically inactive and can survive outside the cell.
It does not replicate. The
reticulate body
is metabolically
active and cannot survive outside the cell. The 48-hour
growth cycle starts with attachment of the elementary
body to the susceptible host cell, after which it is ingested
by a process that resembles phagocytosis (Fig. 41-5).
Once inside the cell, the elementary body transforms
into the larger
reticulate body
, which then commandeers
the host cell’s metabolic machinery to fuel its replica-
tion. The reticulate body divides repeatedly for up to
36 hours, forming new elementary bodies that are released
when the infected cell bursts. Necrotic debris elicits
inflammatory and immune processes that further dam-
age infected tissue.
The signs and symptoms of chlamydial infection resem-
ble those produced by gonorrhea. The most significant dif-
ference between chlamydial and gonococcal salpingitis is
that chlamydial infections may be asymptomatic or clini-
cally nonspecific. In women, chlamydial infections may
cause urinary frequency, dysuria, and vaginal discharge.
25,26
The most common symptom is a mucopurulent cervical
discharge. The cervix itself frequently hypertrophies and
becomes erythematous, edematous, and extremely friable.
This can lead to fallopian tube damage and increase the
reservoir for further chlamydial infections. In men, chla-
mydial infections cause urethritis, including meatal ery-
thema and tenderness, urethral discharge, dysuria, and
urethral itching. Prostatitis and epididymitis with subse-
quent infertility may develop. The most serious compli-
cation of untreated chlamydial infection in men is the
development of Reiter syndrome, a reactive arthritis that
includes the triad of urethritis, conjunctivitis, and painless
mucocutaneous lesions (see Chapter 44).
Diagnosis andTreatment
The CDC recommends annual screening of women who
are sexually active and younger than 25 years; men who
have sex with men and have receptive anal sex; and all
HIV-infected individuals who participate in receptive
anal sex.
25
Heterosexual individuals and men who have
sex with men or have multiple and/or anonymous sex
partners should be tested more frequently. A health care
provider may choose to screen more frequently depend-
ing on a person’s sexual risks. All pregnant women
should be tested early in pregnancy; for women with
increased risk factors, third-trimester screening is also
recommended.
25
Diagnosis of chlamydial infections takes several
forms. The identification of polymorphonuclear leuko-
cytes on Gram stain of penile discharge in the man or
cervical discharge in the woman provides presumptive
evidence. The direct fluorescent antibody test and the
enzyme-linked immunosorbent assay, which use anti-
bodies against an antigen in the
Chlamydia
cell wall,
are rapid tests that are highly sensitive and specific.
The positive predictive value of these tests is excellent
among high-risk groups, but false-positive results occur
more often in low-risk groups. The methodological
challenges of culturing this organism have led to the
development of non–culture-based tests that amplify
and detect
C. trachomatis
–specific DNA and RNA
sequences.
25
One of the newer sets of nonculture tech-
niques, the nucleic acid amplification tests (NAATs),
do not require viable organisms for detection, and can
produce a positive signal from as little as a single copy
of the target DNA or RNA.
25
These amplification meth-
ods are highly sensitive and, if properly monitored, very
specific. Because NAATs can be performed on urine and
self-collected swab specimens from the distal vagina as
well as the traditional endocervical and urethral speci-
mens, this easy, convenient means of accurate detection
has become the diagnostic method of choice.
4
Detection
rates (specificity) for chlamydiae in urine and vaginal
samples are nearly identical to those for cervical and
urethral samples.
24
EB
EB
RB
EB attachment
Cell receptor
0 hour
0 hour
8 hours
12 hours
24 hours
30 hours
40 hours
48 hours
Phagocytosis
Transcription
of DNA
RNA and protein
synthesis in EBs
Binary fission
of RB
Reorganization of
EB into reticulate
body (RB)
Continued
multiplication
Host DNA
synthesis declines.
RBs produce their
own macromolecule
of DNA, RNA, and
protein.
Further reorganization
of RBs to EBs
(low infectivity)
Inclusion forms
contain EBs and
RBs
Infectivity
increases
Inclusion forms
contain mostly
EBs
Lysis of
the cells
Release of EBs
Chlamydial
growth
cycle
FIGURE 41-5.
Chlamydial growth cycle.
EB, elementary body; RB, reticulate body.
(FromThompson SE, Washington AE.
Epidemiology of sexually transmitted
Chlamydia trachomatis infections. Epidemiol
Rev. 1983;5:96–123.)
