Porth's Essentials of Pathophysiology, 4e

1057

Sexually Transmitted Infections

C h a p t e r 4 1

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

Phagocytosis

Transcription of DNA

Reorganization of EB into reticulate body (RB)

EB

EB attachment

0 hour

8 hours

RNA and protein synthesis in EBs

0 hour

Binary fission of RB

Cell receptor

12 hours

Host DNA synthesis declines. RBs produce their own macromolecule of DNA, RNA, and protein.

Release of EBs

Chlamydial growth cycle

48 hours

24 hours

Continued multiplication

Lysis of the cells

40 hours

Infectivity increases

30 hours

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.)

RB

Inclusion forms contain mostly EBs

Inclusion forms contain EBs and RBs

Further reorganization of RBs to EBs (low infectivity)

EB