Chlamydia

Chlamydia

Etiology

Chlamydia trachomatis is caused by the gram negative obligate pathogen C. trachomatis.

Epidemiology

Chlamydial infection is recognized as the most prevalent of the sexually transmitted diseases (STDs) in the United States. Because it is not a reportable disease, the actual number of cases is still unknown. It is estimated, however, that each year more than five to six million Americans experience epidemic chlamydial infection.

Chlamydial infections are responsible for about 20 percent  to 30 percent of diagnosed pelvic inflammatory disease, and it is estimated that about 11,000 women annually become involuntarily sterilized and an approximate of 36,000 mothers suffer from ectopic pregnancies as a result of this pathogenic organism. Chlamydial infections can be transmitted to infants during the birth process and delivery of the baby, causing neonatal conjunctivitis (inflammation of the conjunctiva) and pneumonia (infection of the lungs) to many.

It is the leading cause of pneumonia in infants less than 6 months of age. The rate of chlamydial infection with pneumonia is approximately 3 to 10 per 1000 live births and many go as high as 50 to 60 per 1000 live births in areas where Chlamydia trachomatis is considered epidemic. The organism has superseded N. gonorrhoeae as a cause of neonatal conjunctivitis. The incidence of chlamydia is highest in young population; indigent, poverty-stricken, promiscuous, sexually active, unmarried women who live in the inner city and in those who have had a prior history of sexually transmitted disease.

Pathophysiology

Chlamydia trachomatis is a parasite that has specific requirements for adenosine triphosphatase (ATP) and amino acids. There are two specific stages in the life cycle of the pathogenic bacterium. In stage I, the infective stage, the elementary body attaches to the host cell and is ingested through the process of phagocytosis. In stage 2, the elementary body undergoes process of metamorphosis to become a reticulate or initial body. This is considered as the metabolic phase or stage of the life cycle. The initial body duplicates by binary fission and changes into the elementary body. The host cell, which contains the elementary bodies, undergoes lysis, liberating infectious organisms that are capable of reinfecting new cells. Thus, chlamydial infection is likely to occur.

Serotypes L1, L2, and L3 are both responsible for lymphogranuloma venereum, which is common in South Africa and the Far East.

Serotypes D through K cause chlamydial infections. It is estimated that between 20 percent and 40 percent of sexually active women have been exposed to the pathogenic bacterium and have antibody titers to C. trachomatis. Chlamydial infection can be transmitted from male to female through intimate sexual contact and activity. Women could pass on the infection through their infants during vaginal birth and delivery.

Chlamydial trachomatis pneumonia among infants is most often seen in newborns up to 12 weeks of age. Signs and symptoms usually manifest gradually with sharp cough, nasal stuffiness; children fail to gain weight. Symptoms progress to tachypnea (increased in respiratory rate) with wheezing and rales (the sound of crackles) audible on auscultation.