Tag Archives: metronidazole

STI Awareness: Intestinal Parasites

This is a colorized scanning electron micrograph of Giardia lamblia, which is in the process of reproducing via binary fission. Image by Dr. Stan Erlandsen, provided by the CDC's Public Health Image Library.

This colorized scanning electron micrograph shows Giardia lamblia reproducing asexually. Image: Stan Erlandsen, CDC’s Public Health Image Library.

Most sexually transmitted infections are caused by bacteria or viruses, but some are caused by organisms that are classified as completely different lifeforms. Trichomoniasis, for example, is caused by a protozoan organism; protozoa occupy their own kingdom, separate from plants, animals, and bacteria. Intestinal parasites are often protozoan organisms, but can also include parasitic worms (which are members of the animal kingdom). They are spread through contact with fecal matter – and as such, they can be transmitted sexually as well as nonsexually. Intestinal parasites are usually transmitted by fecal contamination of food or water, and are most common in areas with insufficient sewage treatment and untreated water in the wilderness. Some pathogens, however, have low infectious doses, making their sexual transmission more likely.


What has eight flagella and can live in your intestines?


Oral contact with the anus, also called anilingus or rimming, is the primary means of the sexual transmission of these pathogens. Putting fingers or hands in your mouth after they have had contact with the anus is also risky. Other modes of transmission include oral sex, as genitals can be contaminated with feces, as well as sharing sex toys and other equipment. For these reasons, it is very important to use dental dams or latex gloves during contact with the anus; to clean the anus before engaging in rimming; to clean or use condoms on shared sex toys; and to use condoms or dental dams during oral sex. Continue reading

STI Awareness: Trichomoniasis

Trichomonas vaginalis, the parasite responsible for trichomoniasis, is pictured in this electron micrograph adhering to vaginal epithelial cells. Normally pear-shaped, this organism flattens itself out after attaching to the cell in order to maximize surface area between parasite and host. Image courtesy of Antonio Pereira-Neves and Marlene Benchimol, Santa Ursula University, Rio de Janeiro, Brazil

Trichomonas vaginalis, normally pear-shaped, flattens itself out after attaching to vaginal epithelial cells, maximizing surface area between parasite and host. The purple rod-shaped organisms are bacteria. Image courtesy of Antonio Pereira-Neves and Marlene Benchimol, Santa Ursula University, Rio de Janeiro, Brazil

Most sexually transmitted infections are caused by viruses or bacteria. STIs caused by viruses include herpes and genital warts, and the viruses that cause them aren’t even technically living organisms – they are pieces of genetic information that are able to infect a host cell. STIs caused by bacteria include gonorrhea and syphilis; bacteria are microscopic, single-celled organisms with relatively simple cell structures.

But some STIs are caused by other types of living organisms. Protozoan organisms are microscopic and unicellular, like bacteria; unlike bacteria, their cell structures more closely resemble that of the so-called “higher” life forms such as animals and plants. While protozoa are considered to be “animal-like,” they are not animals at all – they are single-celled organisms that reproduce asexually. When certain types of protozoans get into your body, they can cause infections – such as trichomoniasis, the most common curable STI among young females (as well as more females over 40 than previously thought). It is estimated that 7.4 million new cases of trichomoniasis occur annually in the United States; worldwide, there are about 170 million cases each year.

Trichomoniasis, colloquially known as trich, is spread by vaginal or anal intercourse, direct vulva-to-vulva contact, and other activities that involve passing secretions from one partner to another (e.g., sharing sex toys or mutual masturbation). Sexually active people can reduce the risk of contracting trichomoniasis by using latex barriers, such as condoms. Continue reading

STI Awareness: Bacterial Vaginosis and Chancroid

Sexually transmitted infections can be caused by viruses, bacteria, protozoans, and even animals. Bacterial vaginosis and chancroid are both infections caused by bacteria, which means that they can be treated with antibiotics. While bacterial vaginosis only affects people with vaginas, chancroid disproportionately affects people with penises. You can seek diagnosis and treatment for bacterial vaginosis and chancroid at a Planned Parenthood health center, as well as health clinics, private health-care providers, and health departments.

Bacterial vaginosis is caused by an imbalance of bacteria species in the vagina. Image: renjith krishnan / FreeDigitalPhotos.net

Bacterial vaginosis is caused by an imbalance of bacteria species in the vagina. Image: renjith krishnan / FreeDigitalPhotos.net

Bacterial Vaginosis
Bacterial vaginosis seems to be most commonly caused by the bacteria species Gardnerella vaginalis. Scientists aren’t quite sure how this infection is caused, but risk seems to correlate with a change in sexual partners, having multiple sexual partners, douching, or using an intrauterine device; it can also occur in females who have never been sexually active. It is more common in pregnant women. There is no counterpart to this infection in males, although G. vaginalis can be found in their urethras; this raises the possibility that bacterial vaginosis can be sexually transmitted, in which case it could be directly transmitted between two females or indirectly transmitted from one female to another via a male.

Bacterial vaginosis seems to result from an imbalance in the vaginal flora (“flora” is a somewhat fanciful term for the bacteria that live in your body; under normal circumstances they are harmless and even beneficial). Vaginas usually are habitat to a population of bacteria called Lactobacillus, which produce hydrogen peroxide as a byproduct. When the number of Lactobacillus declines, G. vaginalis is able to move in on Lactobacillus’ old territory. The decrease in Lactobacillus and increase in G. vaginalis leads to a rise in the vagina’s pH. The new vaginal environment is less acidic and more alkaline; a vaginal pH of more than 4.5 is one criterion for the diagnosis of bacterial vaginosis. Another symptom includes a vaginal discharge that may smell somewhat fishy. There might also be genital itching or pain during urination. It is also possible not to have symptoms. Continue reading