Rectal douching is associated with gut dysbiosis and metabolic disruption in HIV-uninfected men who have sex with men

Abstract

Background

We aimed to elucidate the effects of rectal douching on gut microbial communities and their associated metabolites in men who have sex with men (MSM).

Methods

A community sample of HIV-uninfected MSM were recruited in Guangzhou, China. Participants were stratified into rectal douching and non-douching groups based on their rectal douching behavior within the past three months. Peripheral blood and fecal samples were collected. Serum markers of microbial translocation were quantified using enzyme-linked immunosorbent assay (ELISA). Gut microbiota composition was assessed via 16S rRNA gene sequencing of fecal samples, and microbial metabolites were profiled using a mass spectrometry-based platform.

Results

This study enrolls a total of 51 HIV-uninfected MSM (20 in the rectal douching group and 31 in the non-douching group). The two groups have comparable age distributions [median age: 25 years, interquartile range (IQR): 23-30 vs. 27 years, IQR: 24-31]. Significant structural shifts in microbial community composition are observed at both the phylum and genus levels in the rectal douching group relative to the non-douching group. The relative abundances of the genera Clostridium, Lachnospira, and Turicibacter are significantly lower in the rectal douching group compared to the non-douching group. Furthermore, rectal douching significantly alters a wide range of microbial metabolites. Notably, rectal douching appears to reduce gut barrier integrity, as evidenced by significantly elevated levels of the microbial translocation marker lipopolysaccharide-binding protein (LBP) in the rectal douching group.

Conclusions

Rectal douching among HIV-uninfected MSM is associated with gut microbiota dysbiosis, significant alterations in microbial metabolic profiles, and reduced gut barrier integrity. These findings underscore the need for increased awareness and health education within this population.

Plain language summary

Some men who have sex with men (MSM) clean their rectum before sex for hygiene, a practice known as rectal douching. While it is common, its effects on gut health are not well understood. We studied two groups of MSM: those who douche and those who do not, comparing their gut bacteria, related metabolites, and gut barrier markers. Our findings show that douching disrupts the balance of gut bacteria, reduces levels of beneficial bacterial products, and may weaken the gut’s protective barrier, potentially increasing infection risk. This reveals a new way that douching can harm gut health, beyond simple physical irritation. Our research underscores the importance of clear health communication about these risks and the need for safer hygiene practices.

Zhao et al. investigate the effects of rectal douching on the gut ecosystem in men who have sex with men. They show that rectal douching is associated with gut microbiota dysbiosis, disrupted microbial metabolite homeostasis, and compromised intestinal barrier integrity.

Introduction

HIV remains a major global public health challenge, with an estimated 42.3 million deaths to date. According to the Joint United Nations Program on HIV/AIDS (UNAIDS), approximately 39.9 million people were living with HIV (PLHIV) globally by the end of 2023, with 1.3 million new infections reported that year¹. Men who have sex with men (MSM) continue to bear a disproportionate burden of the global HIV epidemic. For example, a study conducted in Turkey reported that the majority of new HIV infections were among MSM (41%) and high-risk heterosexuals (38%)². HIV prevalence among MSM is substantially higher than in the general population (0.5%), with reported rates ranging from 1.2% to 32.6% in Latin America^3–5, 38% to 49% in South Africa⁶, 7.5% to 9.9% in Togo⁷, 10.5% to 18.2% in Vietnam⁸, and 5.4% to 6.1% in China⁹.

The high prevalence of HIV among MSM is largely attributable to distinct sexual behaviors, including unprotected anal intercourse (UAI) and multiple sexual partnerships. Recently, literatures reported that rectal douching is associated with increased odds of HIV and other sexually transmitted infections (STIs) among MSM^10–12. Rectal douching refers to the insertion of liquid into the rectum using specialized devices, typically performed for cleansing purposes before or after anal intercourse. Approximately 88% of MSM have engaged in rectal douching, with 87–97% doing so prior to anal sex and 13–48% afterward¹³. Lu et al. reported that the association between rectal douching and increased HIV risk was mediated by UAI and rectal bleeding¹⁴. This is biologically plausible, as rectal bleeding may facilitate HIV transmission by compromising the integrity of the intestinal mucosa.

However, whether rectal douching influences gut microbiota composition remains unclear. The gut microbiota plays a critical role in the development and regulation of the mammalian immune system, while the immune system, in turn, maintains microbiota homeostasis¹⁵. Gut dysbiosis, defined as a detrimental shift in microbial composition, can impair immune responses, disrupt the epithelial barrier, and increase vulnerability to pathogenic invasion¹⁶. Prior research has shown that pathogenic restructuring of the gut microbiota in MSM may occur several months before HIV seroconversion¹⁷, suggesting that specific microbial signatures could enhance susceptibility to HIV infection. Moreover, our previous study demonstrated that the genera Coprococcus, Blautia, and Megamonas were associated with divergent clinical outcomes in HIV-infected MSM after more than 24 months of antiretroviral therapy (ART)¹⁸. However, the lack of rectal douching data in these studies precludes determining whether the observed microbial alterations were attributable to this practice.

The present study aimed to determine whether rectal douching disrupts the rectal microbiota environment in MSM. We show that rectal douching is associated with significant alterations in gut microbiota composition, compromised intestinal barrier integrity, and widespread decreases in microbial metabolites. These findings demonstrate that rectal douching disrupts the gut ecosystem, which may heighten susceptibility to infections and underscore the need for greater awareness of its health risks.

Methods

Study design and participants

HIV-uninfected MSM participants were recruited from a local MSM community-based organization (CBO) in Guangzhou that provides HIV/STI-related services. Participants were stratified into rectal douching and non-douching groups based on their history of rectal douching within the preceding three months. Eligibility criteria included: (1) biologically male; (2) aged 18 years or older; and (3) a history of anal intercourse with men. Exclusion criteria were: (1) use of antibiotics, probiotics, prebiotics, or synbiotics within the past six months; (2) history of gastrointestinal surgery; (3) adherence to specific dietary patterns in the past 6 months, including low-carbohydrate, ketogenic, or vegetarian diets; and (4) presence of active inflammatory or immune-related conditions known to affect gut microbiota, including HIV infection, syphilis, inflammatory bowel disease, gastritis, gastric ulcer, systemic lupus erythematosus, rheumatoid arthritis, autoimmune hemolytic anemia, malignancies, hyperthyroidism, hypertension, diabetes, scleroderma, and primary immune thrombocytopenia.

Ethnicity, sexual orientation, and sexual preferences were self-reported by participants. Ethical approval for this study was obtained from the Ethics Review Board of Sun Yat-sen University (SYSU-SPH2020047). Written informed consent was obtained from all participants prior to enrollment. To ensure participant confidentiality, no personally identifiable information—such as names, contact details, or residential addresses—was collected.

Measures

Peripheral blood and fecal samples were collected from all participants. Blood samples were kept on ice and transported to the laboratory within 4 hours for immediate processing. Serum was separated by centrifugation and stored at −80 °C until analysis. Serum levels of microbial translocation markers—including lipopolysaccharide (LPS), lipopolysaccharide-binding protein (LBP), and soluble cluster of differentiation 14 (sCD14)—were quantified using enzyme-linked immunosorbent assay (ELISA). Gut microbiota composition was assessed by 16S rRNA gene sequencing of fecal samples, while microbial metabolites were profiled using mass spectrometry. Detailed protocols for these procedures have been described in our previous publications^18,19. In brief, total genomic DNA was isolated from stool specimens using a commercial extraction kit (Omega Biotek, USA) according to the manufacturer’s protocol. DNA purity and concentration were measured with a NanoDrop ND‑2000 ultramicro spectrophotometer (Thermo Fisher Scientific, USA), and its size distribution and integrity were verified by 1% agarose gel electrophoresis. The bacterial hypervariable V3–V4 region of the 16S rRNA gene was amplified via polymerase chain reaction (PCR) with universal primers (338F: 5′-ACTCCTACGGGAGGCAGCAG-3′; 806R: 5′-GGACTACHVGGGTWTCTAAT-3′). The final effective 16S rRNA gene sequences had an average length of 414 bp, with a mean of 30,368 high-quality valid sequences obtained per sample.

Additionally, a questionnaire was administered to collect the following information: (1) Sociodemographic characteristics, including age (years), body-mass index (BMI), ethnicity (Han: yes/no), highest level of education, occupation, marital status, defecation frequency in the past month, and fecal form in the past month. (2) Sexual behaviors, including history of anal intercourse (yes/no), history of rectal douching in the past 3 months (yes/no), age at sexual debut (years), sexual orientation (homosexual/bisexual), disclosure of sexual orientation (yes/no), history of sex with women (yes/no), sexual role in the past 6 months, frequency of condom use in the past 6 months, number of anal sex partners in the past 6 months, and lifetime number of anal sex partners.

Statistical analysis

Descriptive statistics for sample characteristics were reported as frequencies and percentages. Differences in categorical variables between the rectal douching and non-douching groups were assessed using the Pearson chi-squared test. Differences in continuous variables were evaluated using the Wilcoxon rank-sum test. Regarding the 16S rRNA gene analysis, taxonomic classification was performed using the SILVA 138 database. Operational taxonomic units (OTUs) were clustered at 97% similarity using the usearch7-uparse pipeline. These OTUs were used to calculate alpha diversity indices (ACE, Chao1, Shannon, Simpson, and Sobs) and to identify the core microbiome. Differences in microbial diversity and taxon abundance between groups were assessed using the Wilcoxon rank-sum test. Spearman’s rank correlation analysis was conducted to examine associations between the relative abundances of differential bacterial genera and microbial metabolites. A two-sided P value < 0.05 was considered statistically significant. All statistical analyses were performed using R software (version 4.4.2; R Core Team, Vienna, Austria). The following R packages were used: corrplot, ggplot2, ggpubr, pheatmap, plotrix, plyr, psych, and reshape2.

Results

Participant characteristics

A total of 51 HIV-uninfected MSM were enrolled in the study, including 20 participants in the rectal douching group and 31 in the non-douching group. The two groups had comparable age distributions, with median ages of 25 years [interquartile range (IQR): 23–30] and 27 years (IQR: 24–31), respectively. Participants in the rectal douching group reported a higher lifetime number of anal sex partners compared to those in the non-douching group (Table 1). No significant differences were observed between the two groups in terms of BMI, defecation frequency in the past month, fecal form in the past month, age at sexual debut, sexual orientation, disclosure of sexual orientation, sexual role in the past 6 months, frequency of condom use in the past 6 months, or the number of anal sex partners in the past 6 months. Detailed sociodemographic and behavioral characteristics of the study cohort were presented in Table 1.

Table 1.

Characteristics of MSM stratified by different status of rectal douching (N = 51)

Variables	Overall (n = 51)	Rectal douching (n = 20)	Non-douching (n = 31)	P-value
Sociodemographic information
Age (years)
Median (IQR)	26 (24–31)	25 (23–30)	27 (24–31)	0.450
18–29	35 (68.6%)	15 (75.0%)	20 (64.5%)	0.850
30–39	15 (29.4%)	5 (25.0%)	10 (32.3%)
40–49	1 (2.0%)	0 (0.0%)	1 (3.2%)
BMI
Median (IQR)	21.95 (19.59–23.36)	22.45 (20.21–23.76)	21.80 (19.38–22.57)	0.159
<18.5	7 (13.7%)	2 (10.0%)	5 (16.1%)	0.747
18.5–24	36 (70.6%)	14 (70.0%)	22 (71.0%)
≥24	8 (15.7%)	4 (20.0%)	4 (12.9%)
Han race
Yes	50 (98.0%)	20 (100.0%)	30 (96.8%)	0.608
No	1 (2.0%)	0 (0.0%)	1 (3.2%)
Live in Guangzhou
Yes	50 (98.0%)	20 (100.0%)	30 (96.8%)	0.608
No	1 (2.0%)	0 (0.0%)	1 (3.2%)
Education
Junior college	9 (17.6%)	4 (20.0%)	5 (16.1%)	0.889
University	33 (64.7%)	13 (65.0%)	20 (64.5%)
Postgraduate	9 (17.6%)	3 (15.0%)	6 (19.4%)
Occupation
Student	12 (23.5%)	5 (25.0%)	7 (22.6%)	0.152
Employed	32 (62.7%)	10 (50.0%)	22 (71.0%)
Unemployed	7 (13.7%)	5 (25.0%)	2 (6.5%)
Marital status
Unmarried	51 (100.0%)	20 (100.0%)	31 (100.0%)	–
Defecation frequency in the past month
1 time per day	31 (60.8%)	13 (65.0%)	18 (58.1%)	0.918
1 time per 2–3 days	7 (13.7%)	2 (10.0%)	5 (16.1%)
2–3 times per day	13 (25.5%)	5 (25.0%)	8 (25.8%)
Fecal form in the past month
Separate hard lumps	1 (2.0%)	0 (0.0%)	1 (3.2%)	0.261
Lumpy and sausage-like	3 (5.9%)	2 (10.0%)	1 (3.2%)
A sausage shape with cracks in the surface	12 (23.5%)	7 (35.0%)	5 (16.1%)
Like a smooth, soft sausage or snake	15 (29.4%)	4 (20.0%)	11 (35.5%)
Soft blobs with clear-cut edges	17 (33.3%)	5 (25.0%)	12 (38.7%)
Mushy consistency with ragged edges	3 (5.9%)	2 (10.0%)	1 (3.2%)
Sexual behaviors
Age of sexual debut (years)
Median (IQR)	20 (18–21)	20 (18–20)	20 (18–22)	0.188
<20	22 (43.1%)	9 (45.0%)	13 (41.9%)	0.528
20–35	29 (56.9%)	11 (55.0%)	18 (58.1%)
Sexual orientation
Homosexual	49 (96.1%)	19 (95.0%)	30 (96.8%)	0.635
Bisexual	2 (3.9%)	1 (5.0%)	1 (3.2%)
Disclosure of sexual orientation
Yes	26 (51.0%)	10 (50.0%)	16 (51.6%)	0.569
No	25 (49.0%)	10 (50.0%)	15 (48.4%)
Disclosure of sexual orientation to parents, brothers, or sisters
Yes	15 (29.4%)	5 (25.0%)	10 (32.3%)	0.409
No	36 (70.6%)	15 (75.0%)	21 (67.7%)
Disclosure of sexual orientation to friends or classmates
Yes	23 (45.1%)	10 (50.0%)	13 (41.9%)	0.390
No	28 (54.9%)	10 (50.0%)	18 (58.1%)
Disclosure of sexual orientation to healthcare providers
Yes	10 (19.6%)	6 (30.0%)	4 (12.9%)	0.128
No	41 (80.4%)	14 (70.0%)	27 (87.1%)
Have sex with women
Yes	4 (7.8%)	0 (0.0%)	4 (12.9%)	0.126
No	47 (92.2%)	20 (100.0%)	27 (87.1%)
Sex role in the past 6 months
Insertive only	15 (32.6%)	4 (22.2%)	11 (39.3%)	0.124
Insertive and receptive	17 (37.0%)	10 (55.6%)	7 (25.0%)
Receptive only	14 (30.4%)	4 (22.2%)	10 (35.7%)
Frequency of condom use in the past 6 months
Always	26 (56.5%)	9 (50.0%)	17 (60.7%)	0.389
Sometimes	18 (39.1%)	9 (50.0%)	9 (32.1%)
Never	2 (4.3%)	0 (0.0%)	2 (7.1%)
Number of anal sex partners in the past 6 months
0	5 (9.8%)	2 (10.0%)	3 (9.7%)	0.449
1	18 (35.3%)	5 (25.0%)	13 (41.9%)
≥2	28 (54.9%)	13 (65.0%)	15 (48.4%)
Number of anal sex partners in lifetime
<5	15 (29.4%)	3 (15.0%)	12 (38.7%)	0.036
6–10	14 (27.5%)	4 (20.0%)	10 (32.3%)
≥11	22 (43.1%)	13 (65.0%)	9 (29.0%)

MSM men who have sex with men, BMI body-mass index, IQR interquartile range. All statistical tests performed were two-sided. Differences in categorical variables between the rectal douching and non-douching groups were assessed using the Pearson chi-squared test. Differences in continuous variables were evaluated using the Wilcoxon rank-sum test.

Alterations in gut microbiota composition and microbial translocation

Analysis of alpha diversity indices—including Sobs, ACE, Chao1, Shannon, and Simpson—revealed a trend toward reduced gut microbiota diversity in the rectal douching group compared to the non-douching group. However, these differences were not statistically significant (Fig. S1A–E).

We subsequently compared abundance-rank profiles of gut microbiota between the two groups. Significant structural shifts in microbial community composition were observed at both the phylum and genus levels in the rectal douching group relative to the non-douching group (Fig. 1). For instance, Actinobacteria accounted for 8.80% of the total phylum-level microbiota and ranked third in the non-douching group, whereas its relative abundance increased to 14.15%, making it the second most abundant phylum in the rectal douching group (Fig. 1A). Additionally, the genera Clostridium, Lachnospira, and Turicibacter exhibited significantly lower relative abundances in the rectal douching group compared to the non-douching group (Fig. 2).

Fig. 1. Community structure of microbiota.

A The relative abundance of gut microbiota at the phylum level. B The relative abundance of gut microbiota at the genus level.

Fig. 2. The relative abundance of differential microbiota at the genus level.

A The relative abundance of Clostridium. B The relative abundance of Lachnospira. C The relative abundance of Turicibacter. Statistical differences were evaluated using the Wilcoxon rank-sum test. All statistical tests performed were two-sided. * 0.01 ≤ P < 0.05, ** 0.001 ≤ P < 0.01.

Notably, serum levels of the microbial translocation marker LBP were significantly higher in the rectal douching group [median: 27.4 ng/mL, IQR: 14.8–59.7] than in the non-douching group [median: 14.2 ng/mL, IQR: 9.0–29.1], suggesting that rectal douching may compromise intestinal mucosal integrity (Fig. 3).

Fig. 3. Microbial translocation.

A Serum level of LPS. B Serum level of LBP. C Serum level of sCD14. LPS lipopolysaccharide, LBP lipopolysaccharide binding protein, sCD14 soluble cluster of differentiation 14. Statistical differences were evaluated using the Wilcoxon rank-sum test. All statistical tests performed were two-sided. *P < 0.05.

Altered fecal metabolite profiles

Given the critical role of the gut microbiota in regulating host metabolism, we further investigated whether rectal douching was associated with alterations in microbial metabolites. A total of 174 metabolites were quantified from fecal samples collected from the 51 enrolled MSM participants. These metabolites were classified into 16 distinct categories, as illustrated in Fig. S2.

Rectal douching significantly modulated the fecal metabolite profile. Notably, the majority of differential metabolites—including 2-Hydroxy-2-methylbutyric acid, 3-Hydroxyhippuric acid, Benzoic acid, Carnitine, Citric acid, Glyceric acid, N-Acetyl-D-glucosamine, Phthalic acid, Propionic acid, Rhamnose, and Serine—were present at significantly lower levels in the rectal douching group compared to the non-douching group. In contrast, Myristoleic acid was significantly elevated in the rectal douching group (Fig. 4).

Fig. 4. The relative abundance of differential microbial metabolites.

The horizontal axis corresponds to each sample, while the vertical axis corresponds to each metabolite.

Correlations between gut microbiota and metabolites

To explore the relationship between gut microbiota and microbial metabolites, Spearman correlation analysis was performed between differential bacterial genera and significantly altered metabolites. Clostridium exhibited positive correlations with 3-Hydroxyhippuric acid (r = 0.47) and Carnitine (r = 0.59), while Turicibacter was positively correlated with both Carnitine (r = 0.36) and Rhamnose (r = 0.36) (Fig. 5). In contrast, Lachnospira showed a negative correlation with Myristoleic acid (r = −0.33) (Fig. 5).

Fig. 5. Correlation between the differential genera and microbial metabolites.

Spearman’s rank correlation analysis was performed to evaluate associations. * 0.01 ≤ P < 0.05, ** 0.001 ≤ P < 0.01, *** P < 0.001.

Discussion

To the best of our knowledge, this is one of the first studies to investigate the impact of rectal douching on gut microbiota composition and associated microbial metabolites in HIV-uninfected MSM. We found that rectal douching was associated with an altered gut microbiota composition in this population. Although alpha diversity indices showed non-significant reductions in the rectal douching group, marked compositional shifts were observed at both the phylum and genus levels. Notably, the genera Clostridium, Lachnospira, and Turicibacter exhibited decreased relative abundances in the rectal douching group compared to the non-douching group. In parallel, elevated levels of the microbial translocation marker LBP suggested reduced gut barrier integrity associated with rectal douching. Furthermore, rectal douching was linked to reduced levels of multiple gut microbial metabolites.

Rectal douching is common among MSM, primarily for hygiene and to enhance sexual experiences^10–13. However, awareness of its potential health risks remains limited. Li et al. reported a significant association between rectal douching and HIV infection among MSM (odds ratio [OR] = 2.8)¹⁰. This association is biologically plausible, as commonly used douching tools—such as shower hoses and enema bottles—can damage the rectum’s single-layer epithelium, cause epithelial denudation, and thereby increase susceptibility to HIV infection^20,21. In addition, most MSM use tap water or soap-based solutions as their primary douching agents²². These hypoosmotic solutions exert lower osmotic pressure than intestinal fluid, leading to water absorption into epithelial cells, which may induce cellular toxicity, lysis, and exacerbate mucosal injury²³. Supporting this mechanism, data from our study showed significantly elevated serum LBP levels in rectal douching users, suggesting an associated reduction in intestinal barrier integrity. LBP is a biomarker of microbial translocation—a process in which gut microbiota and their products cross a compromised intestinal barrier, enter the bloodstream or extraintestinal tissues, and trigger chronic immune activation²⁴. A previous study demonstrated that elevated microbial translocation levels were positively correlated with CD4+ T cell counts in the gastrointestinal tract²⁵, potentially contributing to increased HIV susceptibility.

In addition to causing mechanical trauma to the rectal mucosa, rectal douching disrupts the indigenous rectal microbiota. Our analysis revealed significantly decreased relative abundances of the genera Clostridium, Lachnospira, and Turicibacter in MSM who practiced rectal douching compared to non-douching controls. The human gastrointestinal tract harbors approximately 10¹⁴ commensal microbial cells that exist in symbiosis with the host and play essential roles in maintaining metabolic homeostasis and regulating immune responses²⁶. Together, a balanced microbiota and an intact mucosal immune system form the intestinal immune barrier, which serves as a primary defense against pathogen invasion²⁷. Microbial dysbiosis can disrupt these physiological processes and has been implicated in the pathogenesis of various diseases, including inflammatory bowel disease, cardiovascular disease, and diabetes mellitus²⁸. Therefore, the observed reductions in Clostridium, Lachnospira, and Turicibacter in douching MSM may impair mucosal immunity, potentially increasing susceptibility to HIV and other STIs. Notably, MSM who engage in rectal douching are more likely to assume the receptive role during anal intercourse. This behavioral pattern is considered a potential contributor to the higher HIV prevalence among receptive partners²⁹, as douching has been associated with an increased risk of HIV acquisition¹⁰. Proposed biological mechanisms include mechanical mucosal injury and perturbation of the local microbiome, which may compromise mucosal integrity and immunity. Additionally, we found that MSM who engage in rectal douching reported a higher lifetime number of anal sex partners, potentially increasing their risk of HIV infections and other STIs.

Unsurprisingly, MSM in the rectal douching group exhibited reduced metabolic capacity, as evidenced by significantly lower levels of numerous fecal metabolites compared to the non-douching group. The intestinal mucosa contains approximately 70% of the body’s immune cells, making it the largest immunological compartment in the human body³⁰. Microbial metabolites—particularly short-chain fatty acids (SCFAs)—mediate critical crosstalk between gut microbiota and immune cells. These metabolites are essential for regulating host energy metabolism³¹ and maintaining the homeostasis of immune cell phenotypes and functions^32,33. The reduced metabolite levels observed in MSM who engage in rectal douching may impair mucosal T cell trafficking, differentiation, and energy regulation, thereby contributing to chronic subclinical immune dysfunction and heightened vulnerability to HIV infection.

This study had several limitations. First, it employed a cross-sectional design, as fecal samples were collected at a single time point. This precluded the assessment of temporal dynamics in gut microbiota following rectal douching. Future longitudinal studies with larger sample sizes are warranted to monitor post-enema microbial shifts and to determine the time required for the restoration of microbial homeostasis. Second, the frequency of rectal douching during the preceding three months was not assessed, which limited our ability to establish a dose–response relationship between rectal douching practices and the extent of gut microbiota dysbiosis.

In summary, this study demonstrated that rectal douching was associated with gut microbiota dysbiosis, disrupted microbial metabolite homeostasis, and compromised intestinal barrier integrity among HIV-uninfected MSM who engaged in rectal douching within the past three months. These findings highlight the need for increased awareness and health education regarding the potential risks of rectal douching and its implications for HIV transmission. Targeted interventions should be developed and disseminated by healthcare professionals and community organizations to promote safer sexual health practices in MSM populations. The development of enema products that minimize harm to gut microbiota is warranted.

Author contributions

This study was conceived and designed by Huachun Zou and Linghua Li. Heping Zhao, Anping Feng and Dan Luo were responsible for data compilation and data analysis. All authors have contributed to the interpretation of data and study findings. Heping Zhao and Fenqi Da drafted the paper with all authors critically reviewing the paper.

Peer review

Peer review information

Communications Medicine thanks the anonymous reviewers for their contribution to the peer review of this work. A peer review file is available.

Data availability

The datasets generated and/or analyzed during the current study are provided as Supplementary Data files.

Code availability

All custom code used for data preprocessing is not publicly available, but is available from the corresponding author on reasonable request.

Competing interests

The authors declared no competing interests.

Supplementary information

The online version contains supplementary material available at 10.1038/s43856-026-01490-0.