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 /

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

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.

It is important to seek treatment for suspected bacterial vaginosis if you are pregnant, as the infection can lead to complications in your pregnancy. Bacterial vaginosis also makes you more vulnerable to infection by HIV and other STIs. Rarely, it can spread to the uterus or fallopian tubes where it can cause pelvic inflammatory disease.

Fortunately, bacterial vaginosis is treatable with drugs such as metronidazole or clindamycin, which kill some bacteria but not others, allowing Lactobacillus to reestablish its population in the vagina. Any medication you are given should be taken as directed and not discontinued earlier than prescribed – if you stop taking it early, the “bad” bacteria might not be under full control and could reestablish themselves, causing your infection to recur. Douching, even with a hydrogen-peroxide-based douche, is not an effective treatment. The consumption of dairy or non-dairy yogurt (whose live cultures include Lactobacillus species) is not clinically proven as an effective remedy for bacterial vaginosis when it is taken in lieu of antibiotics, although it might enhance the effects of antibiotics when both are taken together.

More information about bacterial vaginosis can be found at the Centers for Disease Control and Prevention’s website.

Microscopic image of Haemophilus ducreyi, the bacteria species responsible for chancroid infections. Image by Dr. N. J. Fiumara, courtesy of the CDC's Public Health Image Library.

Microscope image of Haemophilus ducreyi, the bacteria species responsible for chancroid infections. Image by Dr. N. J. Fiumara, courtesy of the CDC’s Public Health Image Library.

Chancroid is caused by a bacteria species called Haemophilus ducreyi; its habitat includes our mucous membranes. Infections by these bacteria are very rare in the United States and rarer still in Arizona, where our dry weather stands in stark contrast to the tropical climates where chancroid is more common. Furthermore, it affects males at a greater rate than it affects females; according to the World Health Organization, this is possibly due to chancroid disproportionately affecting some sex-worker populations, whose clients are almost entirely male. Also, as cited in a 2006 systematic review, uncircumcised males are at increased risk for chancroid, which scientists hypothesize is due to the warm and moist environment the foreskin provides for bacteria. Many U.S. physicians are unfamiliar with this STI, which might cause difficulties in diagnosis and underreporting of its prevalence.

Symptoms of chancroid usually appear within 10 days of initial infection, and can include the formation of a swollen, open sore on the genitals. The lymph nodes in the genital region also become infected, and might swell to the point of breaking through to the skin’s surface, where they can release pus. Because chancroid can also be transmitted via oral sex, the infection can manifest itself in the oral cavity, such as the lips or tongue, where lesions can form. When lesions are present, the risk for transmitting other STIs, such as HIV, is increased. Chancroid symptoms can often be confused with those of other STIs, such as herpes or syphilis, so it’s important to get a diagnosis from a professional.

Chancroid is spread by the skin-to-skin contact inherent to most sexual activities, or by contact with pus from a chancroid sore. Risk for chancroid is correlated with multiple sex partners (15 to 20 partners per year, according to WHO). Sexually active people can reduce their risk of contracting chancroid by using latex barriers, such as condoms and dental dams. If you suspect that you or your partner has a chancroid sore, avoid contact with it as the pus from such sores can spread the bacteria.

Chancroid is diagnosed by examining pus collected from lesions and checking it for the presence of H. ducreyi. It is treated with certain antibiotics, such as erythromycin. In rare cases, it is possible for the lesions to lead to permanent scarring. More information can be found at Planned Parenthood’s website.

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