C. trachomatis is a small gram-negative bacterium that is an obligate intracellular pathogen. It exists in two forms. The infectious form, the elementary body, is capable of at least limited survival in the extracellular environment. The elementary body is taken up by host cells, primarily through a process of receptor-mediated endocytosis. Once inside the cell, the elementary body differentiates into a metabolically active form, termed the reticulate body. Using the energy sources of the host cell, the reticulate body replicates and ultimately forms new infectious elementary bodies, which have a tropism for columnar epithelial cells.
C. trachomatis infections are associated with a wide range of clinical features that are virtually indistinguishable from those caused by N. gonorrhoeae. Clinically, patients typically present 1 to 5 weeks after exposure with dysuria with or without urethral discharge. Patients may develop epididymitis, prostatitis, pelvic inflammatory disease, pharyngitis, conjunctivitis, perihepatic inflammation, and, among individuals who engage in anal sex, proctitis. It is the most common cause of epididymitis in young men. Similar to gonococcus, a large percentage of both men and women are asymptomatic. C. trachomatis also causes lymphogranuloma venereum (LGV), discussed in the next section. The infection may be transmitted to newborns during vaginal birth, where up to 15% of exposed newborns develop chlamydial pneumonia and 50% develop chlamydial conjunctivitis.
The morphologic and clinical features of chlamydial infection, with the exception of lymphogranuloma venereum, are virtually identical to those of gonorrhea. The primary infection is characterized by a watery to mucopurulent discharge that contains a predominance of neutrophils. Organisms are not visible in Gram-stained sections. In contrast with the gonococcus, C. trachomatis cannot be isolated with the use of conventional culture media. The diagnosis is best made by a nucleic acid amplification test on voided urine, which is now the gold standard. Another important manifestation of chlamydial infection is reactive arthritis (formerly known as Reiter syndrome), predominantly in patients who are HLA-B27 positive. This condition typically manifests as a combination of urethritis, conjunctivitis, arthritis, and generalized mucocutaneous lesions.
http://ebooksmedicine.net •NGUandcervicitisarethemostcommonformsofSTD.MostcasesarecausedbyC. trachomatis, andtherestbyT. vaginalis,
M. genitalium and U. urealyticum.
C. trachomatis isagram-negativeintracellularbacteriumthatcausesadiseasethatisclinicallyindistinguishablefromgonorrheainbothmenandwomen.Diagnosiscanbemadebysensitivenucleicacidamplificationtestsinurinesamplesorvaginalswabs.
InpatientswhoareHLA-B27positive,C. trachomatis infectioncancausereactivearthritisalongwithconjunctivitisandgeneralizedmucocutaneouslesions.
LGV is a chronic, ulcerative disease caused by certain strains of C. trachomatis that are distinct from those causing the more common nongonococcal urethritis or cervicitis discussed earlier. It is endemic in parts of Asia, Africa, the Caribbean region, and South America. An increased incidence has been noted in the US in the past 15 years, due in large part of infections in men having sex with men, who are often co infected with HIV. As in the case of granuloma inguinale (discussed later), sporadic cases of LGV are seen most often among individuals with multiple sexual partners.