Emerging resistance in genital mycoplasmas: 6-year trends of Ureaplasma spp. and Mycoplasma hominis infections in Eastern China

Abstract

Background

To investigate the epidemiological profile and antimicrobial resistance patterns of genital mycoplasma in Eastern China and provide evidence-based guidance for clinical management.

Methods

A retrospective analysis was conducted on clinical records, mycoplasma culture results, and antimicrobial susceptibility testing data from patients with suspected urogenital tract infections between 2018 and 2023.

Results

Among 47,619 suspected infected patients, 20,830 cases tested positive for genital mycoplasma infection, with an overall infection rate of 43.74%. The infection rate of pure Ureaplasma spp. was 37.00%, for pure Mycoplasma hominis (Mh) was 0.66%, and for the co-infections with Ureaplasma spp. and Mh was 6.08%. The infection rate in females (44.00%) was significantly higher than that in males (20.12%), with a statistically significant difference (P < 0.001). The observed changes in each age group showed statistically significant differences (P < 0.001). Seasonally, the infection rate of mycoplasma in spring was slightly higher than that in winter. Regarding drug resistance, genital mycoplasmas generally exhibited a higher resistance rate to fluoroquinolone drugs, while the resistance rates to tetracycline, doxycycline, pristinamycin, and josamycin were relatively low. The average resistance rates to ciprofloxacin and ofloxacin in patients with pure Ureaplasma spp. infections were relatively high, at 83.39% and 66.34%, respectively. And the resistance rates showed an increasing trend year by year (P < 0.001). Patients with pure Mh infections had the highest resistance rate to ofloxacin (80.32%), followed by ciprofloxacin (69.21%), with no significant differences in resistance rates across the years. Patients co-infected with Ureaplasma spp. and Mh had the highest average resistance rates to both ofloxacin and ciprofloxacin, exceeding 90.00%.

Conclusion

The infection rate of genital mycoplasma in Eastern China is relatively high, predominantly Ureaplasma spp., with significant resistance to fluoroquinolone drugs. It is necessary for the hospital to enhance monitoring for the genital mycoplasma infections and to conduct drug resistance analysis to guide rational medication use and infection control measures.

Clinical trial number

Not applicable.

Introduction

Genitourinary tract infections (GUIs) are a common public health concern worldwide, and mycoplasma is one of the most common pathogens, including Ureaplasma urealyticum (Uu), Ureaplasma parvum (Up), Mycoplasma hominis (Mh), and Mycoplasma genitalium, which can result in a range of genitourinary disorders, including nongonococcal urethritis, prostatitis, cervicitis, salpingitis, and even infertility and neonatal infections in severe cases [1–3]. Due to the absence of cell walls in mycoplasma, effective antimicrobial agents are limited to those targeting DNA replication inhibition (e.g., fluoroquinolones like ofloxacin and ciprofloxacin) or protein synthesis disruption (tetracyclines including tetracycline and doxycycline; macrolides such as erythromycin, clarithromycin, azithromycin, and josamycin; streptogramins exemplified by pristinamycin). However, the widespread clinical application of these antimicrobial classes, compounded by increasing unstandardized therapeutic practices, has consequently driven a significant rise in mycoplasma resistance to multiple agents. This resistance is most likely to be attributed to genetic mutations or the acquisition of resistance determinants [4–6]. The infection rate and drug resistance of genital mycoplasma vary significantly between different regions [7–9], therefore, understanding the infection status and drug resistance characteristics of mycoplasma in a specific region is crucial for developing effective preventive and therapeutic measures.

The objective of this study was to investigate the prevalence of genital mycoplasma in the Suzhou region in recent years, its distribution across different age groups, genders and seasons, and the trend of drug resistance. This investigation was conducted by analyzing the clinical data of patients with suspected genitourinary tract infections who attended a tertiary care hospital in Suzhou from 2018 to 2023. The findings of this study are intended to provide a reference for the clinical diagnosis and treatment of genital mycoplasma infections.

Materials and methods

Subjects

A total of 47,619 patients with suspected genitourinary tract infections were selected for the study. These patients attended the department of gynecology, obstetrics, urology and the reproductive center of the Affiliated Suzhou Hospital of Nanjing Medical University from January 2018 to December 2023. The inclusion criteria for the study were as follows: the subject must have presented at the clinic with clinical symptoms related to genitourinary tract infection, such as urinary frequency, urgency, dysuria, abnormal urethral discharge, perineal discomfort, pelvic pain, and other symptoms; and the subject must not have been treated with antimicrobial drugs in the week prior to sampling. The following individuals were excluded from the study: women who were menstruating; patients with co-infections of Neisseria gonorrhoeae and/or Chlamydia, as well as mycoplasma infections in other body parts. This study was a retrospective observational analysis based on laboratory data. All analyzed data were obtained from the laboratory information system that underwent strictly anonymized processing, and does not involve the acquisition or use of any patient personal privacy information. The requirement for informed consent was waived by the Ethics Committee of The Affiliated Suzhou Hospital of Nanjing Medical University (Approval No. K-2024-144-K01). The study was conducted in accordance with the local legislation and institutional requirements.

Methods

The samples were collected from the patients in accordance with the stipulated requirements of the 4th edition of the National Clinical Laboratory Procedures. The mycoplasma culture, identification, enumeration and drug sensitivity test kits Mycoplasma IST 2 (bioMérieux, SA, France) were utilized to culture and identify Ureaplasma spp. and Mh of the collected samples, and to determine their sensitivity to nine commonly used antimicrobial drugs (pristinamycin, erythromycin, clarithromycin, azithromycin, ofloxacin, tetracycline, doxycycline, josamycin and ciprofloxacin) concurrently. It should be noted that when using this test strip, both Uu and Up were collectively regarded as Ureaplasma spp. The antibiotic resistance breakpoints (mg/L) for the above nine antibiotics were as follows: pristinamycin, resistant (R) ≥ 2; erythromycin, R ≥ 4; clarithromycin, R ≥ 4; azithromycin, R ≥ 4; ofloxacin, R ≥ 4; tetracycline, R ≥ 8; doxycycline, R ≥ 8; josamycin, R ≥ 8; and ciprofloxacin, R ≥ 2 [9, 10]. The test results were interpreted in strict accordance with the kit instructions. The counting section assesses whether the number of mycoplasmas in the tested sample equals or exceeds the threshold value set at 10⁴ CCU (colour-changing units).

Statistical analyses

Statistical analyses were performed using SPSS Statistics version 27.0 (IBM Corp., Armonk, NY, USA). Categorical variables were presented as absolute numbers (n) with proportions (%). Intergroup comparisons were conducted using either the chi-squared test or Fisher’s exact test, as appropriate. The statistical significance threshold was defined as α = 0.05 (two-tailed).

Results

Prevalence of Ureaplasma spp. and Mh

Among 47,619 suspected genital mycoplasma infection cases, 20,830 tested positive, yielding an overall positivity rate of 43.74%. The stratified prevalence included 17,620 (37.00%) Ureaplasma spp. monoinfection, 315 (0.66%) Mh monoinfection, and 2,895 Ureaplasma spp.+ Mh (6.08%) coinfections. Temporal analysis revealed significant downward trends in positivity rates from 2018 to 2023, reaching nadir values in 2022 at 32.67% (Ureaplasma spp.), 0.46% (Mh), and 5.12% (co-infections), respectively. Year-to-year comparisons demonstrated statistically significant variations across all infection categories (P < 0.001). Detailed annual breakdowns are presented in Table 1.

Table 1.

Detection rates of Mycoplasma in 47,619 Chinese samples (2018–2023)

Years	Number	Prevalence
		Ureaplasma spp. (%)	Mh (%)	Ureaplasma spp. + Mh (%)	Total (%)
2018	6692	2792(41.72%)	86(1.29%)	415(6.20%)	3293(49.21%)
2019	5953	2373(39.86%)	28(0.47%)	399(6.70%)	2800(47.04%)
2020	4851	1757(36.22%)	30(0.62%)	308(6.35%)	2095(43.19%)
2021	11,303	4159(36.80%)	69(0.61%)	759(6.72%)	4987(44.12%)
2022	10,691	3493(32.67%)	49(0.46%)	547(5.12%)	4089(38.25%)
2023	8129	3046(37.47%)	53(0.65%)	467(5.74%)	3566(43.87%)
Total (%)	47,619	17,620(37.00%)	315(0.66%)	2895(6.08%)	20,830(43.74%)
x2		173.058	50.226	31.794	239.975
P		< 0.001	< 0.001	< 0.001	< 0.001

Data are reported as number and percent within parentheses. The chi-squared test was used for statistical analysis

Mh: Mycoplasma hominis

Demographic and seasonal distribution of urogenital Mycoplasma infections

Among 47,619 suspected cases, females demonstrated significantly higher positivity rates than males (χ² = 116.226, P < 0.001). Age-stratified analysis revealed substantial variations across groups (χ² = 598.033, P < 0.001), with the highest infection rate observed in the < 21 years cohort (59.13%) and the lowest in the > 50 years group (29.51%). Seasonal distribution patterns showed a peak of positivity in spring (44.57%) compared to the winter trough (42.44%), which reached statistical significance (χ² = 11.906, P = 0.008). Detailed stratified data are shown in Table 2.

Table 2.

Demographic and seasonal distribution of urogenital Mycoplasma infections

Characteristics	Category	Tested cases (n)	Positive cases (n)	Positivity rate (%)	χ2	P
Sex	Male	507	102	20.12	116.226	< 0.001
	Female	47,112	20,728	44.00
Age groups (years)	< 21	734	434	59.13	598.033	< 0.001
	21–30	16,206	7746	47.80
	31–40	18,663	8062	43.20
	41–50	6970	3099	44.46
	> 50	5046	1489	29.51
Season	Spring (March-May)	12,151	5416	44.57	11.906	0.008
	Summer (June-August)	13,354	5907	44.23
	Autumn (September-November)	12,402	5385	43.42
	Winter (December-February)	9712	4122	42.44

Changes in drug resistance of genital Mycoplasma from 2018 to 2023

Analysis of 17,620 cases of Ureaplasma spp.-positive drug susceptibility results showed that there were significant differences in the resistance of Ureaplasma spp.-infected patients to nine drugs. The rate of Ureaplasma spp. resistance to ofloxacin showed a significant increasing trend, from 59.67% in 2018 to 68.98% in 2023 (χ² = 20.212, P < 0.001); the rate of resistance to ciprofloxacin showed a slow increasing trend, from 79.33% to 85.03% in 2023 (χ² = 45.452, P < 0.001); the resistance rates to erythromycin, azithromycin, clarithromycin and tetracycline showed an overall decreasing trend (P < 0.05), with an average rate of less than 3%; and the resistance rates to pristinamycin, doxycycline and josamycin were maintained at a lower level (< 1%) and the changes between years were not significantly different. Detailed data are presented in Fig. 1.

Fig. 1.

Temporal trends in resistance rates of Ureaplasma spp. to nine antibiotics (2018–2023)

From 2018 to 2023, Mh-infected patients had the highest mean resistance rate to ofloxacin at 80.32%, followed by ciprofloxacin (69.21%), while resistance rates to doxycycline, pristinamycin, josamycin and tetracycline remained low (0.00% ~ 5.66%). The resistance rates of Mh-infected patients to common drugs did not change significantly. Detailed data are presented in Fig. 2.

Fig. 2.

Temporal trends in resistance rates of Mh to six antibiotics (2018–2023)

From 2018 to 2023, the average resistance rate to ciprofloxacin was the highest in Ureaplasma spp. + Mh co-infected patients, reaching 96.93%, followed by ofloxacin (93.92%). The resistance rates to doxycycline, pristinamycin, crospovidomycin, and tetracycline in Ureaplasma spp. + Mh co-infected patients remained low (1.30% ~ 7.77%); the resistance rates to ofloxacin (χ² = 11.642, P = 0.040) and pristinamycin (χ² = 11.489, P = 0.042) changed statistically significantly. Specific data are shown in Fig. 3.

Fig. 3.

Temporal trends in resistance rates of Ureaplasma spp.-Mh to six antibiotics (2018–2023)

Discussion

Mycoplasma is a class of the smallest prokaryotic cell-type microorganisms without cell walls, of which Ureaplasma spp. and Mh are two closely related to human genitourinary tract infections, and they often colonize the human genitourinary tract, which can trigger infections and lead to a variety of diseases in times of immunocompromise or microenvironmental changes [11–13]. The results of this study showed that the positive rate of mycoplasma detection was 43.74% in 47,619 genitourinary tract specimens sent for examination in Suzhou from 2018 to 2023, with simple Ureaplasma spp. infections being the most common (37.00%), followed by mixed Ureaplasma spp. + Mh infections (6.08%), and simple Mh infections being the least common (0.66%), which is consistent with the report of Wang et al. [14]. The total mycoplasma infection rate was lower than that in Xi’an area (47.11%) [15], but higher than that reported in Hangzhou (38.1%) and Shenyang (37.5%) [8, 10]. Mycoplasma positivity rates reported abroad also varied, e.g., 39.40% in South Korea and 31.87% in northeastern Romania [16, 17]. Differences in mycoplasma positivity rates in the genitourinary tract in different regions may be related to regional climate, socioeconomic conditions, culture of the population, standard of living, and concepts of sexual life.

In terms of gender, the positive rate of mycoplasma infections was found to be significantly higher in females than in males in this study (P < 0.001), which is consistent with the report of Song and Kasprzykowska et al. [9, 10, 18]. While our study observed a higher detection rate of urogenital mycoplasmas in women, which may be attributed to anatomical and physiological factors such as thinner vaginal mucosa, greater exposure as the receptive partner during intercourse, and hormonal fluctuations during menstruation or pregnancy [19, 20], the role of male carriers cannot be overlooked. Asymptomatic colonization of Ureaplasma species in the male urogenital tract represents a significant reservoir for transmission and recurrent infections in female partners. Beyond its epidemiological significance, growing evidence indicates that Ureaplasma infection in men is associated with impaired reproductive health, particularly infertility [21, 22]. Multiple mechanisms may underlie this effect, including bacterial adherence to spermatozoa, reactive oxygen species generation, cross-reactive antibody production, and reduction of essential sperm proteins such as P34H and hyaluronidase, ultimately impairing sperm motility and fertilizing capacity [23, 24]. Therefore, although often clinically silent, male urogenital colonization with Ureaplasma species has important implications for both transmission dynamics and reproductive outcomes. These findings underscore the need for increased awareness of male screening and partner management strategies in preventing persistent and recurrent infections.

The age of the individual has been identified as a pivotal determinant in the epidemiology of sexually transmitted infections. A significant proportion, constituting nearly 80%, of genitourinary mycoplasma infections were observed in the 21–40 age group, a finding that aligns with the observations reported by Zheng et al. This observation may be attributed to the fact that individuals in these age groups are in their reproductive years and are sexually active. This underscores the necessity for enhanced surveillance measures in this specific population [25]. It is noteworthy that, although the age group under 21 years had the lowest number of infected persons (434), which was much lower than other age groups, it had the highest infection rate of 59.13%.

In addition, as a highly mobile urban center, Suzhou exhibits significant seasonality of mycoplasma (2018–2023), with a winter decline reaching its lowest point in February, followed by a spring surge. This result is similar to previous research on other sexually transmitted diseases in China such as gonorrhea, syphilis, and chlamydia infections [26–28], which may be related to China’s “Spring Festival effect” [29]: the outflow of migrant workers reduces sexual activity and healthcare during holidays, while returning home after holidays promotes the recovery in March, so it is necessary to strengthen publicity and education activities during population mobility.

Mycoplasma is not sensitive to penicillin, cephalosporins, and other β-lactam antimicrobial drugs due to the absence of cell wall [30]. The available active antimicrobial drugs for this organism are limited to tetracyclines, macrolides, and fluoroquinolones. Recent years have seen an increase in the prevalence of genital mycoplasma resistance, with concomitant reports of multi-drug resistance [6, 31]. In the present study, the resistance rate of genital mycoplasma to fluoroquinolones (ofloxacin and ciprofloxacin) was generally high and tended to increase year by year, especially in Ureaplasma spp. - Mh mixed infections, where the average rate of resistance was more than 90%, which is consistent with the reports from other regions of China [10, 18, 32]. It is worth noting that the level of resistance to fluoroquinolones can vary significantly between countries. For example, in Italy, 39.5% of Ureaplasma species were resistant to ciprofloxacin [31]. In France, however, Mycoplasma strains exhibited very low quinolone resistance rates, at < 1.2% for Ureaplasma spp. and < 2.7% for Mh [33]. This major difference may be related to different regions’ strategies or tendencies regarding the use of antibiotics. In contrast, the increase in quinolone resistance rates in China may be attributed to multiple factors, including its frequent use in treating a wide range of infections, not just Mycoplasma, due to its broad-spectrum antimicrobial activity [34, 35], good oral absorption, and its inappropriate application in poultry farming [36]. Fluoroquinolone resistance in Mycoplasma is predominantly linked to mutations in the QRDRs of gyrA, gyrB, parC, and parE genes—particularly S83L, S83W, and R448K mutations [23, 37, 38]. Among these, the S83L mutation in parC is strongly correlated with high-level resistance [18, 39, 40]. Furthermore, the majority of clinical isolates exhibited minimal resistance to tetracyclines (e.g., tetracycline, doxycycline) and streptomycins (e.g. pristinamycin), with resistance levels ranging from 0.00 to 7.77%. The majority of the clinical Ureaplasma spp. isolates exhibited low levels of resistance to erythromycin, clarithromycin, and azithromycin (0.80 to 3.47%). Given the inherent resistance of Mh to C14 and C15 member macrolides (i.e., erythromycin, azithromycin, and clarithromycin) [41], the analysis of resistance to these drugs in uncomplicated Mh infections and Ureaplasma spp. - Mh co-infections were not undertaken. In the majority of clinical isolates, there was a continued low level of resistance to C16 macrolides (josamycin). The findings of this study indicate that macrolides, tetracyclines, and streptomycins are effective for treating uncomplicated Ureaplasma spp. infections in this region. In contrast, tetracyclines, doxycycline, josamycin, and pristinamycin are more efficacious for infections associated with simple Mh infections or mixed Ureaplasma spp. - Mh infections. The antimicrobial susceptibility differences observed among genital mycoplasma isolates from various regions underscore the importance of local surveillance of antimicrobial resistance to inform empirical treatment strategies.

However, it is important to note that this study is not without its limitations. Firstly, due to the absence of other clinical data for participants, the study is unable to distinguish between actual genital mycoplasma infections and common commensal bacterial colonization. Secondly, the Mycoplasma IST2 kit, along with several other kits currently available, cannot differentiate between Ureaplasma parvum (Up) and Ureaplasma urealyticum (Uu). Typically, the detection of a single serovar of Up is common in clinically asymptomatic carriage, and most are considered part of the normal flora. At present, our nation has kits for Ureaplasma species typing detection available in medical facilities. The extensive utilization of typing tests will effectively diminish the misjudgment of the clinical significance of Ureaplasma spp. positivity, which is of significant importance for standardizing the use of antimicrobial drugs and reducing overtreatment [18]. Thirdly, given that all clinical isolates of Ureaplasma spp. and Mh were generated as part of routine clinical laboratory procedures and were discarded after testing, the identification and antimicrobial susceptibility test results obtained from the Mycoplasma IST2 kit cannot be compared with molecular-based methods or standard guidelines from the Clinical and Laboratory Standards Institute (CLSI) on antimicrobial susceptibility tests. Therefore, we will further investigate the resistance mechanisms of Ureaplasma spp. and Mh to fluoroquinolones, macrolides, and tetracyclines in the future.

Conclusion

In conclusion, the present study identified a relatively high prevalence of mycoplasma infections in the genitourinary tract of Suzhou, with Ureaplasma spp. being the predominant species. Furthermore, a number of significant gender and age differences were also observed. It is noteworthy that the rate of resistance to quinolones almost reached the threshold of clinical efficacy, indicating the necessity for antimicrobial stewardship programs. However, it should be noted that the study was conducted in a single center and used a retrospective design, which may have influenced the extrapolation of results. It is recommended that drug sensitivity testing be prioritized before clinical treatment, and that a regional resistance monitoring network be established. It is recommended that public health interventions focus on educational initiatives for the high-risk demographics identified in this study.

Abbreviations

Mh

Mycoplasma hominis

GUIs

Genitourinary tract infections

Author contributions

YQZ drafted the manuscript. NS and LH participated in the acquisition of data. WDX and YNW designed the study. JJG reviewed and edited the manuscript for intellectual content. All authors read and approved the final manuscript.

Funding

Supported by Suzhou Key Laboratory of Intelligent Critical Illness Biomarkers Translational Research (SZS2024029); Suzhou Medical and Health Technology Innovation Project (SYWD2025145; SYWD2024326); Nanjing Medical University - Qilu Clinical Research Fund Project (2024KF0258).

Data availability

The datasets used or analyzed during this study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

The study protocol was approved by the Ethics Committee of The Affiliated Suzhou Hospital of Nanjing Medical University (Approval No. K-2024-144-K01). This is a retrospective study. The need for informed consent was waived by the Ethics Committee of The Affiliated Suzhou Hospital of Nanjing Medical University. This study was conducted in full accordance with the Declaration of Helsinki.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.