Discharge Characteristics Comparison: Mycoplasma genitalium, Gonorrhea, and Chlamydia
Gonorrhea produces the most profuse and purulent discharge, while both Mycoplasma genitalium and chlamydia cause mucopurulent or less profuse discharge—though symptoms alone cannot reliably differentiate these pathogens. 1
Comparative Discharge Characteristics Table
| Feature | Gonorrhea | Chlamydia | Mycoplasma genitalium |
|---|---|---|---|
| Discharge Volume | Most profuse and obvious [1] | Less profuse than gonorrhea [1] | Mucopurulent, less profuse [1] |
| Discharge Appearance | Purulent, thick, yellow-green [1] | Mucopurulent, clear to white or slightly yellow [1] | Mucopurulent [1] |
| Spontaneous Visibility | Often visible without urethral stripping [1] | Usually requires urethral stripping to visualize [1] | Requires urethral stripping [1] |
| Microscopy Findings | Abundant PMNs (>5 WBC/HPF); gram-negative intracellular diplococci [1] | ≥10 WBC/HPF in first-void urine sediment [1] | Non-specific inflammation, similar to chlamydia [1] |
| Symptomatic Presentation | More commonly symptomatic [2] | 53-100% of extragenital infections asymptomatic [2] | More symptomatic urethritis than chlamydia despite similar microscopy [1] |
| Cervicitis Presentation | Yellow endocervical exudate [3] | Yellow endocervical exudate [3] | Yellow endocervical exudate [3] |
Critical Clinical Limitations
The CDC explicitly states that symptoms and discharge characteristics alone cannot differentiate these pathogens—nucleic acid amplification testing (NAAT) is required for definitive diagnosis. 1
Key Diagnostic Pitfalls:
- Up to 50% of women with gonorrhea or chlamydia have no mucopurulent cervicitis despite active infection 1
- Mucopurulent cervicitis is not a sensitive predictor of infection—in most MPC cases, neither gonorrhea nor chlamydia can be isolated 3, 4
- All three pathogens can present with mucopurulent or purulent discharge 1
- Asymptomatic infections are common across all three pathogens 1, 2
Practical Clinical Algorithm
When Evaluating Urethral/Vaginal Discharge:
Perform Gram stain microscopy if available to identify gram-negative intracellular diplococci (gonorrhea) versus non-specific inflammation 1
Obtain NAAT testing for all three pathogens (N. gonorrhoeae, C. trachomatis, and M. genitalium) in symptomatic patients 1
Treat empirically for both gonorrhea and chlamydia if any of the following apply: 4
- Local prevalence is high (>15%)
- Patient unlikely to return for follow-up
- Patient is sexually active and under 25 years old
- Patient seen in STD clinic or high-prevalence setting
Specific Prevalence Data:
- M. genitalium detected in 26.8% of urethritis cases, 21.1% of vaginitis, 11.8% of cervicitis, and 15.4% of PID 5
- M. genitalium present in 9% of asymptomatic males and 15.4% of asymptomatic females 5
- Overall M. genitalium prevalence in sexual health clinics: 16.6% 5
Important Treatment Consideration
Macrolide resistance in M. genitalium is 59.1%, so azithromycin should not be used without resistance testing. 5 This is particularly relevant because M. genitalium causes more symptomatic urethritis than chlamydia despite similar discharge characteristics. 1