Question

Chlamydia trachomatis and Neisseria gonorrhoeae infections are often asymptomatic. What are the consequences of having an asymptomatic infection? Each of these pathogens has one or more mechanisms that promote host infection. Describe these (give 2 examples) mechanisms for one of these pathogens.

Answer 1

Chlamydia trachomatis

Chlamydia is a common sexually transmitted disease (STD) caused by infection with Chlamydia trachomatis. It can cause cervicitis in women and urethritis and proctitis in both men and women. Chlamydia trachomatis infections is asymptomatic. However, given the relatively slow replication cycle of the organism, symptoms may not appear until several weeks after exposure in those persons who develop symptoms.

Chlamydia can infect the rectum in men and women, either directly (through receptive anal sex), or possibly via spread from the cervix and the muscular tube leading from the external genitals to the cervix of the uterus in women and most female in a woman with cervical chlamydial infection. However these infections are often asymptomatic and they can cause symptoms of proctitis (e.g., rectal pain, discharge, and/or bleeding).

Chlamydia can also be found in the throats of women and men having oral sex with an infected partner, but it is typically asymptomatic and an important cause of pharyngitis.

Chlamydial infections in women can lead to serious consequences including pelvic inflammatory disease (PID), tubal factor infertility, ectopic pregnancy, and chronic pelvic pain. Lymphogranuloma venereum (LGV).

Neisseria gonorrhoeae

Gonorrhea is a common sexually transmitted disease (STD) caused by infection with Neisseria gonorrhoeae. It can infect both men and women and cause infections in the genitals, rectum, and throat. Some men with gonorrhea are asymptomatic.  Most women with gonorrhea do not have any symptoms. Even when a woman has symptoms, they are often mild and can be mistaken for a bladder or infectiion of the muscular tube leading from the external genitals to the cervix of the uterus.  Most women with gonorrhea are at risk of developing serious complications from the infection, even they are asymptomatic.

In males, the disease starts as acute urethrits with a mucopurulent discharge and infection extends along the urethra to the prostate, seminal vesicles and epididymis. Chronic urethritis may lead to stricture formation.

In females, The initial infection involves the urethra and cervix uteri. The infection may extend to the Bartholin's glands, endometrium and Fallopian tubes. Salpingitis may lead to sterility.

Proctitis occurs in both sexes and conjunctivitis may also occur.

Mechanisms that promote host infection in gonorrhea

1. The first step in infection is adhesion of gonococci to urethra or other mucosal surfaces. Pili are involved in adhesion. Pili are hair like structures which enhance attachmant to host cells and resistance to phagocytosis. They are made up of stacked pilin proteins. The pilins are antigenically different and a single strain can make several antigenically different forms of pilin. Hence here adhesion is rapid and firm so that micturition after exposre offers no protection against infection.. The cooci penetrates through intracellular spaces and reach the sub-epithelial connective tissue by the third day after infection.

2. Toxicity in gonococci is largely due the presence of endotoxin lipopolysaccharide. During infection, bacterial lipooligosaccharide (LOS) and peptidoglycan are released by autolysis of cells. Both bacterial polysaccharides activate the host’s alternative complement pathway, while lipooligosaccharide stimulates the production of tumor necrosis factor (TNF) which causes cell damage. Neutrophils are then attracted to the site and feed on the bacteria. lipooligosaccharide produces mucosal damage in fallopian tube organ cultures and brings about the release of enzymes, such as proteases and phospholipases . Thus, gonococcal lipooligosaccharide plays important role in mediating tissue damage.