Fungal Infections of the Reproductive System
By the end of this section, you will be able to:
- Summarize the important characteristics of vaginal candidiasis
Only one major fungal pathogen affects the urogenital system. Candida is a genus of fungi capable of existing in a yeast form or as a multicellular fungus. Candida spp. are commonly found in the normal, healthy microbiota of the skin, gastrointestinal tract, respiratory system, and female urogenital tract (shown below). They can be pathogenic due to their ability to adhere to and invade host cells, form biofilms, secrete hydrolases (e.g., proteases, phospholipases, and lipases) that assist in their spread through tissues, and change their phenotypes to protect themselves from the immune system. However, they typically only cause disease in the female reproductive tract under conditions that compromise the host’s defenses. While there are at least 20 Candida species of clinical importance, C. albicans is the species most commonly responsible for fungal vaginitis.
As discussed earlier, lactobacilli in the vagina inhibit the growth of other organisms, including bacteria and Candida, but disruptions can allow Candida to increase in numbers. Typical disruptions include antibiotic therapy, illness (especially diabetes), pregnancy, and the presence of transient microbes. Immunosuppression can also play a role, and the severe immunosuppression associated with HIV infection often allows Candida to thrive. This can cause genital or vaginal candidiasis, a condition characterized by vaginitis and commonly known as a yeast infection. When a yeast infection develops, inflammation occurs along with symptoms of pruritus (itching), a thick white or yellow discharge, and odor.
Other forms of candidiasis include cutaneous candidiasis (see Mycoses of the Skin) and oral thrush (see Microbial Diseases of the Mouth and Oral Cavity). Although Candida spp. are found in the normal microbiota, Candida spp. may also be transmitted between individuals. Sexual contact is a common mode of transmission, although candidiasis is not considered an STI.
Diagnosis of vaginal candidiasis can be made using microscopic evaluation of vaginal secretions to determine whether there is an excess of Candida. Culturing approaches are less useful because Candida is part of the normal microbiota and will regularly appear. It is also easy to contaminate samples with Candida because it is so common, so care must be taken to handle clinical material appropriately. Samples can be refrigerated if there is a delay in handling. Candida is a dimorphic fungus, so it does not only exist in a yeast form; cultivation can be used to identify chlamydospores and pseudohyphae, which develop from germ tubes (shown below). The presence of the germ tube can be used in a diagnostic test in which cultured yeast cells are combined with rabbit serum and observed after a few hours for the presence of germ tubes. Molecular tests are also available if needed. The Affirm VPIII Microbial Identification Test, for instance, tests simultaneously for the vaginal microbes C. albicans, G. vaginalis (see Bacterial Infections of the Urinary System), and Trichomonas vaginalis (see Protozoan Infections of the Urogenital System).
Topical antifungal medications for vaginal candidiasis include butoconazole, miconazole, clotrimazole, tioconazole, and nystatin. Oral treatment with fluconazole can be used. There are often no clear precipitating factors for infection, so prevention is difficult.
Check Your Understanding
What factors can lead to candidiasis?
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Did your answer mention:
How is candidiasis typically diagnosed?
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Did your answer mention:
Clinical Focus. Part 3
The Gram stain of Nadia’s vaginal smear showed that the concentration of lactobacilli relative to other species in Nadia’s vaginal sample was abnormally low. However, there were no clue cells visible, which suggests that the infection is not bacterial vaginosis. But a wet-mount slide showed an overgrowth of yeast cells, suggesting that the problem is candidiasis, or a yeast infection (shown below). This, Nadia’s doctor assures her, is good news. Candidiasis is common during pregnancy and easily treatable.
- Knowing that the problem is candidiasis, what treatments might the doctor suggest?
The case continues in Protozoan Infections of the Urogenital System. The case began in Anatomy and Normal Microbiota of the Urogenital Tract.
Summary
- Candida spp. are typically present in the normal microbiota in the body, including the skin, respiratory tract, gastrointestinal tract, and female urogenital system.
- Disruptions in the normal vaginal microbiota can lead to an overgrowth of Candida, causing vaginal candidiasis.
- Vaginal candidiasis can be treated with topical or oral fungicides. Prevention is difficult.
Key terms
- candidiasis — fungal infection caused by Candida spp., especially C. albicans; can affect various regions of the body, e.g., skin (cutaneous candidiasis), oral cavity (oral thrush), or vagina (yeast infection).
Practice
Summarize the important characteristics of vaginal candidiasis
Which medication is recommended as an initial topical treatment for genital yeast infections?
Penicillin and acyclovir are not antifungal drugs at all; between the two antifungals that remain, the module lists one separately as an oral treatment, apart from its topical list.The most common Candida species associated with yeast infections is ________.
The module gives this as the one species, out of at least 20 of clinical importance, most often responsible for fungal vaginitis.A fungal infection caused by Candida spp. that can affect the skin, oral cavity, or vagina is called ________.
The vaginal form of this infection is commonly known as a yeast infection.Although sexual contact is a common mode of transmission for Candida spp., candidiasis is not considered a(n) ________.
Think of the general category for an infection passed between sexual partners — the module says this one does not count as that, despite the transmission route.Candida spp. can secrete ________ (e.g., proteases, phospholipases, and lipases) that assist in their spread through tissues.
These are the class of enzymes that break down host tissue components; the parenthetical names three specific examples.Vaginal candidiasis can be treated with topical or oral ________.
This is the Key Concepts and Summary’s general term for antifungal drugs, whether applied to the skin or taken by mouth.Candida is a ________ fungus, so it does not only exist in a yeast form.
This is the general term for a fungus capable of existing in more than one morphological form.Which of the following antifungal medications for vaginal candidiasis is taken orally rather than applied topically?
The module lists five drugs as topical treatments in one sentence, then names a sixth, different drug as an oral treatment in the next.This section is adapted from Microbiology, Section 23.5: Fungal Infections of the Reproductive System by Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster, and OpenStax, © OpenStax, licensed under CC BY-NC-SA 4.0. Access the original for free at openstax.org. Changes: all three figures are re-encoded as WebP and rendered as mediafigures, kind="photo" set explicitly on all three after image inspection (all photomicrographs, matching the manifest’s guess), with the first figure carrying eager="true"; the Candida blastospores/chlamydospores figure’s alt is rewritten because the source alt names only “chlamydospores” and “blastospores,” omitting the third label the image itself prints and arrows to, “pseudohyphae” — reported as a suspected source alt defect; the germ-tube figure’s alt is kept as printed (it names all three of the image’s labels accurately); the Clinical Focus figure’s alt is lightly reworded from the source’s “a) … B) …” lettering to this book’s own “(a)/(b)” style, with no change to what it describes; the module’s two source exercises (one Multiple Choice, one Fill in the Blank) are rendered as keyed, in source option order; the Multiple Choice’s own stem prints “Which oral medication is recommended as an initial topical treatment for genital yeast infections?,” self-contradictory upstream (miconazole, the keyed answer, is the topical agent the module lists; fluconazole is the oral one), so a careful learner reading “oral” literally is misled into the wrong option — the word “oral” is dropped from the stem here (now “Which medication is recommended as an initial topical treatment for genital yeast infections?”), options and key unchanged; both body Check Your Understanding bullets (“What factors can lead to candidiasis?” and “How is candidiasis typically diagnosed?”) remain body self-checks, since each needs more than one module sentence assembled into an honest answer; the Clinical Focus Part 3 box is rendered as a callout, its closing “jump to the next / go back to the previous Clinical Focus box” links replaced with a plain sentence naming that the case continues in Protozoan Infections of the Urogenital System and began in Anatomy and Normal Microbiota of the Urogenital Tract (the module’s own “previous” link points at Bacterial Infections of the Reproductive System, where Part 2 sits, not at where the case began), and its closing discussion question kept as unanswered bulleted prose, as printed; the cross-reference to Mycoses of the Skin is rendered as a link to this book’s authored section; the cross-reference to Microbial Diseases of the Mouth and Oral Cavity stays plain italicized text, since that chapter is not yet authored; the cross-references to Bacterial Infections of the Urinary System and Protozoan Infections of the Urogenital System are rendered as links to their pages, both landing in this run; this section’s one learning objective is below the book’s usual per-section floor, so its single Practice group carries the section-level floor of 8 items rather than the ordinary 3, per this run’s decision; of those 8 items, the 2 source exercises are graded as keyed, and the other 6 are author-written from this module’s own sentences — a term-recall textin from the Key terms bullet, an STI-classification cloze and a hydrolases cloze from the body, a “dimorphic” cloze from the diagnosis sentence, and a “fungicides” cloze and a topical-versus-oral multiplechoice from the treatment sentences — because the module’s own exercise set is the shortest of this chapter’s six sections; key terms are compiled from the module’s one <term> element, giving one bullet, its meaning taken from the book’s Glossary appendix; no source exercise, table, or Check Your Understanding bullet is omitted; this module has no footnotes and no Disease Profile table of its own (the candidiasis row is folded into the Disease Profile table in Protozoan Infections of the Urogenital System).