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Neurosyphilis cannot be diagnosed using a single test. With or without clinical signs, it is generally necessary to assess a variety of factors, including reactive serologic test results, cerebrospinal fluid cell count abnormalities, cerebrospinal fluid protein abnormalities, or reactive VDRL-CSF (the VDRL test of cerebrospinal fluid). The VDRL-CSF is highly specific, but not sufficiently sensitive for conclusive diagnosis.

The recommended treatment for syphilis is parenteral penicillin G (especially long-acting benzathine penicillin, although the exact choice depends on the stage of disease). Other options include tetracycline and doxycycline .

a) micrograph of a spiral cell. b) micrograph of many spiral cells.
(a) Darkfield micrograph of Treponema pallidum. (b) Silver stain micrograph of the same species. (credit a, b: modification of work by Centers for Disease Control and Prevention)

Congenital syphilis

Congenital syphilis is passed by mother to fetus when untreated primary or secondary syphilis is present. In many cases, infection may lead to miscarriage or stillbirth. Children born with congenital syphilis show symptoms of secondary syphilis and may develop mucus patches that deform the nose. In infants, gummas can cause significant tissue damage to organs and teeth. Many other complications may develop, such as osteochondritis , anemia , blindness, bone deformations, neurosyphilis, and cardiovascular lesions. Because congenital syphilis poses such a risk to the fetus, expectant mothers are screened for syphilis infection during the first trimester of pregnancy as part of the TORCH panel of prenatal tests.

  • What aspect of tertiary syphilis can lead to death?
  • How do treponemal serologic tests detect an infection?

Chancroid

The sexually transmitted infection chancroid is caused by the gram-negative rod Haemophilus ducreyi . It is characterized by soft chancres ( [link] ) on the genitals or other areas associated with sexual contact, such as the mouth and anus. Unlike the hard chancres associated with syphilis, soft chancres develop into painful, open sores that may bleed or produce fluid that is highly contagious. In addition to causing chancres, the bacteria can invade the lymph nodes, potentially leading to pus discharge through the skin from lymph nodes in the groin. Like other genital lesions, soft chancres are of particular concern because they compromise the protective barriers of the skin or mucous membranes, making individuals more susceptible to HIV and other sexually transmitted diseases.

Several virulence factors have been associated with H. ducreyi , including lipooligosaccharide s, protective outer membrane proteins, antiphagocytic proteins , secretory proteins, and collagen-specific adhesin NcaA . The collagen-specific adhesion NcaA plays an important role in initial cellular attachment and colonization. Outer membrane proteins DsrA and DltA have been shown to provide protection from serum-mediated killing by antibodies and complement.

H. ducreyi is difficult to culture; thus, diagnosis is generally based on clinical observation of genital ulcers and tests that rule out other diseases with similar ulcers, such as syphilis and genital herpes. PCR tests for H. ducreyi have been developed in some laboratories, but as of 2015 none had been cleared by the US Food and Drug Administration (FDA). Centers for Disease Control and Prevention. “2015 Sexually Transmitted Diseases Treatment Guidelines: Chancroid,” 2015. http://www.cdc.gov/std/tg2015/chancroid.htm. Recommended treatments for chancroid include antibiotics such as azithromycin , ciprofloxacin , erythromycin and ceftriaxone . Resistance to ciprofloxacin and erythromycin has been reported. Ibid.

a) Photo of a white swelling on a penis. B) micrograph of rod shaped pink cells.
(a) A soft chancre on the penis of a man with chancroid. (b) Chancroid is caused by the gram-negative bacterium Haemophilus ducreyi , seen here in a gram-stained culture of rabbit blood. (credit a, b: modification of work by Centers for Disease Control and Prevention)
  • What is the key difference between chancroid lesions and those associated with syphilis?
  • Why is it difficult to definitively diagnose chancroid?

Bacterial reproductive tract infections

Many bacterial infections affecting the reproductive system are transmitted through sexual contact, but some can be transmitted by other means. In the United States, gonorrhea and chlamydia are common illnesses with incidences of about 350,000 and 1.44 million, respectively, in 2014. Syphilis is a rarer disease with an incidence of 20,000 in 2014. Chancroid is exceedingly rare in the United States with only six cases in 2014 and a median of 10 cases per year for the years 2010–2014. Centers for Disease Control and Prevention. “2014 Sexually Transmitted Disease Surveillance,” 2015. http://www.cdc.gov/std/stats14/default.htm. [link] summarizes bacterial infections of the reproductive tract.

Table title: Bacterial Infections of the Reproductive Tract. Columns: Disease, Pathogen, Signs and Symptoms Transmission, Diagnostic Tests, Antimicrobial Drugs. Disease - Bacterial vaginosis (BV); Gardnerella vaginalis, Bacteroides spp., Fusobacterium spp., others; Often asymptomatic; vaginal discharge, burning, odor, or itching Opportunistic infection caused by imbalance of normal vaginal microbiota; Vaginal smear; Clindamycin, metronidazole, tinidazole. Disease – Chancroid; Haemophilus ducreyi; Soft, painful chancres on genitals, mouth, or anus; swollen lymph nodes; pus discharge; Sexual contact or contact with open lesions or discharge; Observation of clinical symptoms and negative tests for syphilis and herpes; Azithromycin, ceftriaxone, erythromycin, ciprofloxacin. Disease - Chlamydia ; Chlamydia trachomatis; Often asymptomatic; in men, urethritis, epididymitis, orchitis; in women, urethritis, vaginal discharge or bleeding, pelvic inflammatory disease, salpingitis, increased risk of cervical cancer ; Sexual contact or from mother to neonate during birth; NAAT, urine sample, vaginal swab, culture; Azithromycin, doxycycline, erythromycin, ofloxacin, or levofloxacin. Disease – Gonorrhea; Neisseria gonorrhoeae; Urethritis, dysuria, penile or vaginal discharge, rectal pain and bleeding; in females, pelvic pain, intermenstrual bleeding, pelvic inflammatory disease, salpingitis, increased risk of infertility or ectopic pregnancy; in disseminated infections, arthritis, endocarditis, meningitis; Sexual contact ; Urine sample or culture, NAAT, PCR, ELISA; Ceftriaxone, azithromycin. Syphilis; Treponema pallidum Primary: hard chancre; Secondary: rash, cutaneous lesions, condylomata, malaise, fever, swollen lymph nodes; Tertiary: gummas, cardiovascular syphilis, neurosyphilis, possibly fatal; Sexual contact or from mother to neonate during birth; Darkfield or brightfield silver stain examination of lesion tissue or exudate, treponemal and non-treponemal serological testing, VDRL-CSF for neurosyphilis, prenatal TORCH panel; Penicillin G, tetracycline, doxycycline.

Key concepts and summary

  • Bacterial vaginosis is caused by an imbalance in the vaginal microbiota, with a decrease in lactobacilli and an increase in vaginal pH. G. vaginalis is the most common cause of bacterial vaginosis, which is associated with vaginal discharge, odor, burning, and itching.
  • Gonorrhea is caused by N. gonorrhoeae , which can cause infection of the reproductive and urinary tracts and is associated with symptoms of urethritis. If left untreated, it can progress to epididymitis, salpingitis, and pelvic inflammatory disease and enter the bloodstream to infect other sites in the body.
  • Chlamydia is the most commonly reported STI and is caused by C. trachomatis . Most infections are asymptomatic, and infections that are not treated can spread to involve the epididymis of men and cause salpingitis and pelvic inflammatory disease in women.
  • Syphilis is caused by T. pallidum and has three stages, primary, secondary, and tertiary. Primary syphilis is associated with a painless hard chancre lesion on genitalia. Secondary syphilis is associated with skin and mucous membrane lesions. Tertiary syphilis is the most serious and life-threatening, and can involve serious nervous system damage.
  • Chancroid is an infection of the reproductive tract caused by H. ducreyi that results in the development of characteristic soft chancres .

Fill in the blank

Soft chancres on the genitals are characteristic of the sexually transmitted disease known as _____.

chancroid

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Short answer

Compare gonococcal and nongonoccocal urethritis with respect to their symptoms and the pathogens that cause each disease.

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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