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Urogenital Mycoplasmoses

Q: What virulence factors are characteristic of Ureaplasma urealyticum?

Characteristic features of Ureaplasma urealyticum include: Urease — an enzyme hydrolyzing urea into toxic ammonia and carbon dioxide.Hydrogen peroxide — a mycoplasma metabolic byproduct.Hemolysins — substances causing erythrocyte lysis.Urease activity serves as a differential marker; urea is required for growth.

For medical students2 min readUpdated 2026-10-10

Urogenital mycoplasmoses are a group of inflammatory diseases of the urogenital tract caused by microorganisms of the family Mycoplasmataceae. The primary source of infection is always an infected human, and the predominant mode of transmission is sexual.

Main pathogensM. hominis, U. urealyticum, M. genitalium.

Pathogenicity thresholdPathogen titer exceeds 10⁴ CFU/mL.

ImmunityNot established; antibodies lack protective properties.

Epidemiology and Transmission

The sole reservoir for urogenital mycoplasmoses is an infected human. In the vast majority of cases, transmission occurs sexually.

However, certain species (M. hominis and U. urealyticum), which can be part of the normal vaginal microbiota, also exhibit a vertical transmission mechanism. This means microorganisms can infect the fetus during passage through infected birth canals. In such cases, infection can lead to neonatal pneumonia.

Clinical Manifestations and Pathogenesis

Symptoms and localization of the inflammatory process directly depend on the specific pathogen and the patient's sex.

M. genitalium: in men, this microorganism causes nongonococcal urethritis. In women, the infection involves the internal reproductive organs, leading to cervicitis, endometritis, and salpingitis.
U. urealyticum: associated with nongonococcal urethritis in men (detected in approximately 10% of such cases).
M. hominis: clinical significance is particularly high in women, being closely associated with salpingitis. Furthermore, this pathogen is linked to postpartum and postabortion fever.

Immune Response

A key feature of urogenital mycoplasmoses is the lack of robust immunity following infection. Post-infection immunity does not develop.

Although specific humoral antibodies are produced, they are present in very low titers. These antibodies lack protective properties and cannot prevent reinfection.

Laboratory Diagnostics

Clinical specimens submitted to the laboratory include urethral swabs, vaginal discharge, or urine samples.

Key interpretation principle: Because M. hominis and U. urealyticum are often part of the normal urogenital microbiota, mere detection is insufficient for diagnosis. The main pathogenicity criterion is a quantitative threshold (titer) exceeding $10^4$ CFU/mL.

Identification methods: Specialized test systems determine the exact species and titer. Biochemical differentiation relies on enzymatic activity:

M. hominis — metabolizes the amino acid arginine.
U. urealyticum — exhibits pronounced urease activity (hydrolyzes urea).

Mnemonic

Remember biochemical properties easily: UREaplasma breaks down UREa.

Frequently asked questions

Which antibiotic groups are used for targeted treatment of urogenital mycoplasmoses?

Antibiotics acting intracellularly or targeting protein/DNA synthesis are used because these pathogens lack a cell wall. Drug classes include:

Macrolides — targeted therapy (azithromycin, clarithromycin, roxithromycin, spiramycin, midecamycin, erythromycin).
Tetracyclines — broad-spectrum intracellularly penetrating agents.
Fluoroquinolones — drugs of choice affecting DNA synthesis.
Lincosamides — used within antimicrobial regimens.

Which culture media are used for bacteriological plating of urogenital mycoplasmoses?

Complex nutrient media are used because these microorganisms are fastidious. Media components include:

Base medium — heart and brain extracts, yeast extract, and serum.
Cholesterol — an essential supplement required for cell membrane synthesis.
Urea — a specific supplement required for ureaplasma growth.

What virulence factors are characteristic of Ureaplasma urealyticum?

Characteristic features of Ureaplasma urealyticum include:

Urease — an enzyme hydrolyzing urea into toxic ammonia and carbon dioxide.
Hydrogen peroxide — a mycoplasma metabolic byproduct.
Hemolysins — substances causing erythrocyte lysis.
Urease activity serves as a differential marker; urea is required for growth.

Is a qualitative PCR test sufficient to confirm disease caused by U. urealyticum?

No. Because this microorganism can be part of the normal flora, a diagnosis is confirmed only when the quantitative titer exceeds 10⁴ CFU/mL.

Is a person protected from reinfection after successful treatment?

No, post-infection immunity does not develop in mycoplasmoses, and the antibodies produced do not serve a protective function.

Can maternal mycoplasmosis harm the child?

Yes, passing through infected birth canals can transmit M. hominis or U. urealyticum to the fetus, potentially causing neonatal pneumonia.

Go deeper

Mechanisms of mycoplasma adhesion to urogenital epithelium
Specifics of clinical specimen collection in men and women
Principles of test systems for quantitative CFU/mL determination
Differential diagnosis of nongonococcal urethritis