Diagnostic assessment of Mycoplasma genitalium in culture-positive women

Abstract

Detection of Mycoplasma genitalium-mediated, chlamydia-negative nongonococcal urethritis and other M. genitalium-linked infectious etiologies has been very challenging. Although M. genitalium is considered a leading cause of genitourinary symptoms in men and women, extreme difficulties in its cultivation due to its highly fastidious nature and the lack of routine and effective diagnostic tests have slowed the generation of clinical data which directly implicate the presence of M. genitalium in disease pathogenesis. In this study, we compared enzyme-linked immunosorbent assays (ELISAs) and immunoblot and PCR assays in M. genitalium culture-positive women over 1 to 3 years of clinical visits to determine the usefulness of independent diagnostic strategies. Furthermore, the value of combinatorial diagnostic assessments is described, which provides insights into the dynamics of M. genitalium-host interactions. Overall, we show that neither ELISA nor PCR, alone or in combination, provides the sensitivity required to confidently predict the existence of viable M. genitalium organisms in cervical and vaginal samples. Additionally, culture-positive women exhibited a range of antibody responsiveness to M. genitalium based upon ELISA and immunoblot assessments, indicating immune diversity among this high-risk population.

FIG. 1.

(A) Comparative distribution of ELISA values against M. genitalium LAMP antigens among negative control samples (n = 54) and M. genitalium culture-positive serum samples (n = 31) at time of culture. The negative cutoff (OD₄₀₅ = 0.28) was determined as 3 standard deviations above the negative control mean. The numbers above individual bars represent the number of patients in each group. (B) Same as panel A except that ELISA values for the culture-positive group correspond to the clinic visit at which each woman's peak antibody titer was achieved.

FIG. 2.

Immunoblot analysis of serum antibody reactivities to M. genitalium LAMP antigens among negative control and M. genitalium culture-positive women. Lane 1, negative control pooled sera; lanes 2 to 5, representative profiles from culture-positive individuals (corresponding ELISA values are given in parentheses). The band intensities of M. genitalium P146, P140, andP110 were scored as 1+ (lanes 2 and 3), 2+ (lane 4), and 3+ (lane 5) in comparison to the negative control.

FIG. 3.

Six representative serological patterns from M. genitalium culture-positive patients evaluated over multiple visits. Peak antibody levels appeared at the time of mycoplasma isolation (A), 4 months after mycoplasma isolation (B), 3 months prior to mycoplasma isolation with a second peak at 18 months (C), and at the time of isolation with a second peak between 23 and 28 months (D). Patterns E and F show no obvious peak antibody titer throughout the 40-month period. The asterisks indicate the time of M. genitalium isolation.