Disease History, Etiology, and Symptoms

Disease History: 

Microscopic Photo of Chlamydia trachomatis (6) 

Genital Chlamydia is the the most common sexually transmitted disease in the United States and worldwide today(2). The first case of chlamydia reported was in 1907 by Stanislaus von Prowazek in Berlin. (4) 
The genus "chlamydia" includes : Chlamydia pneumoniae, Chlamydia psittaci, and Chlamydia trachomatis (5). Chlamydia trachomatis is the causative strain/pathogen for the STD we know as Chlamydia or "the Clam" in slang. Humans are reservoirs for the bacterium Chlamydia trachomatis(2).  
Interestingly, the word "chlamydia" comes from the greek word "chlamis" which means cloak. The word "trachomatis" is a greek word for rough or harsh (4). The word goes along well with the disease because the STD is known to have little to no symptoms in some individuals. Additionally, the disease is also known as "rough" or "harsh" because it has very bumpy, or rough exterior, as seen in the picture above(2). 

Disease Etiology

Life cycle of chalmydia trachomatis (10)

Chlamydia trachomatis  is a gram negative bacterium that lacks peptidoglycan(5). It has an coccus shape, non motile, and non spore forming (7). Since this bacteria lacks peptidoglycan it is not susceptible to the antibiotic penicillin(5). The mode of action of penicillin is to break down the enzyme that link the peptidoglycan cell wall together (6). However, since the bacterium completely lacks peptidoglycan the antibiotic is completely ineffective. Instead, drugs like azithromycin  and doxycycline are used (9).

This STD has two different stages, the elementary body and reticular body. 

The elementary stage occurs when the initial infection is established. Bacteria in the elementary stage are much like endospores because the outer membrane is highly resistant to the harsh environment (8). Once the elementary body has found a new host (epithelial cells), the host cells engulf the bacterium and the elementary body transitions into a reticulate (non infectious) body. In this state the bacterial must use the host cells ATP to reproduce. Since the bacterium is cloaked instide the hosts cell, the host’s immune system cannot clear the infection. After the reticulate bodies have divided to become elementary bodies they are released from the cell through exocytosis and go on to infect more cells(5). The life cycle is depicted in the picture above. 

Symptoms

CDC STD Surveillance, 2014

The symptoms of Chlamydia are very similar to other STDs such as gonorrhea. Symptoms in women are only seen about 20% of the time(9). However, some symptoms can be seen such as vaginal discharge, abnormal vaginal bleeding, fever, and dysuria. Males only have symptoms 50% of the time. These include urethral discharge, dysuria,swelling, and itching around the testicles(9). Some factors that influence the infection are : unsafe sex(no condom), and previous/present STDs(3). The STD can be detected using DNA/RNA amplification of chlamydia through urine or urethral/vaginal swabs (11). The CDC collects information on STD's yearly and has reported that women have higher rates of chlamydia than males(1). A statistic from 2014 is placed above. It is believed that this disparity is caused by a combination of factors, such as biological differences between males and females, and higher STD screening rates among women (1). Regardless of the reasoning behind the disparity, Chlamydia continues to be the most common STD because of its lack of symptoms (2). From BSCI348M class we know that these statistics are usually unrepresentative of the actual population since these diseases are often under reported. 

Sources:

(1) http://www.cdc.gov/std/chlamydia/

(2) http://jid.oxfordjournals.org/content/201/Supplement_2/S190.full

(3) http://www.prostatitis.org/chlamydia.html

(4) http://www.austincc.edu/microbio/2704q/chlam.htm

(5) http://web.clark.edu/tkibota/240/Disease/Chlamydia.pdf

(6) http://www.iflscience.com/health-and-medicine/strange-history-and-future-chlamydia-vaccines

(7) BSCI443 Lectures

(8) BSCI348M Lectures

(9) http://emedicine.medscape.com/article/214823-medication#2

(10) https://microbewiki.kenyon.edu/images/thumb/a/a0/TaraMcIntyreLifeCycle.jpg/300px-TaraMcIntyreLifeCycle.jpg

(11) http://www.webmd.com/sexual-conditions/guide/chlamydia