Mycoplasma hominis chorioamnionitis associated with preterm delivery: A case report

Abstract

This case report highlights a Mycoplasma hominis infection associated with chorioamnionitis following preterm premature rupture of membranes (PPROM) in a 43-year-old pregnant woman at 30 weeks gestation. The patient presented with a mild fever and increased white cell count, leading to the diagnosis of chorioamnionitis. Empiric antibiotic treatment with ampicillin and gentamicin was initiated, later switched to ceftriaxone. Mycoplasma hominis was identified through routine placental cultures on CDC Anaerobic Blood Agar, and confirmed by whole-genome sequencing (WGS) using the Illumina HiSeq platform. The WGS revealed no resistance mutations to macrolides, quinolones, or tetracyclines, and predicted susceptibility to these antimicrobials. The isolate exhibited a high number of SNP differences (5471–8074) compared to publicly available M. hominis genomes. No specific anti-Mycoplasma treatment was administered, and both mother and newborn had favourable outcomes. This case underscores the importance of considering Mycoplasma infections in pregnancy complications and the need for specialized testing, as routine cultures may fail to detect these organisms. WGS offers a comprehensive approach to pathogen identification and drug resistance profiling, though the clinical impact of targeted antimicrobial therapy for Mycoplasma infections in such cases remains uncertain.

Highlights

• •Rare Mycoplasma hominis chorioamnionitis associated with PROM.
• •Mycoplasma hominis requires special culture conditions and/or PCR for accurate detection, which are often not available in routine diagnostics.
• •Whole-genome sequencing revealed no resistance mutations but showed notable genetic divergence from other strains.

Introduction

Mycoplasma hominis are Mollicutes that do not have cell walls and have been associated with various infections including of the genitourinary tract. Maternal-foetal infections have also been described, with associations reported with adverse outcomes in pregnancy [7]. Mycoplasma cultures require special incubation conditions diagnosis may be missed when only routine bacterial cultures are requested. Cultures may also require several days. Specific testing with polymerase chain reaction (PCR) is another option but may not be available in some laboratories. We report a case of Mycoplasma hominis infection that was cultured on routine bacterial cultures from placenta in association with chorioamnionitis occurring following preterm premature rupture of membranes.

Case presentation

A 43-year-old female G4P1 who at 30 weeks 5 days’ gestation presented with preterm premature rupture of membranes. She has a history of hepatitis B infection, but otherwise no significant medical history. On day 4 of presentation, chorioamnionitis was suspected following an increase in temperature to 37.9°C with a rise in white cell count. Intravenous ampicillin and gentamicin was administered, and labour was induced. This was changed to intravenous ceftriaxone and the patient was discharged on oral amoxicillin-clavulanic acid after two days. Placental cultures were also sent. Mycoplasma hominis grew on CDC Anaerobic Blood Agar (BD Diagnostics, USA) under anaerobic conditions after two days. The isolate was identified using the Bruker MALDI Biotyper (Bruker Corporation, USA), and whole-genome sequencing confirmed the identification. Specific antimicrobials targeted at Mycoplasma were not prescribed but no complications were seen in both patients with apparent resolution following delivery. Antimicrobials of choice include macrolides and quinolones. Treatment is typically empiric as susceptibility testing results are not readily available. However, resistance rates have been increasingly reported [6], [7].

The genomic DNA was extracted and sequenced using the Illumina HiSeq 2000 platform producing 2x150bp paired-end reads. The average sequencing depth was 1,220X. Mycoplasma hominis was predicted as the bacterial species using KmerFinder 3.2 (https://cge.food.dtu.dk/services/KmerFinder/). Genome assembly was performed using SPAdes with an N50 of 96,757 bp. Assembly completeness was assessed with BUSCO v4.1.2 analysis with the mycoplasmatales_odb10 database, revealing 100 % Complete BUSCOs score. MYC02 has a genome size of 675, 639 bp (G+C content ∼ 27 %).

The presence of SNPS were detected by mapping read-mapping to drug resistance associated loci using M. hominis MIN-132 as reference (NCBI RefSeq assembly:GCF_021460215.1). In M. hominis, intrinsic resistance to macrolides and telithromycin is linked to a G2057A transition in domain V of 23S rRNA gene, as well as to ribosomal protein genes rplD (L4) and rplV (L22)[4]. No polymorphisms were found in 23S rRNA gene or in L4 and L22. Additionally, the quinolone resistance-determining regions (QRDR) of DNA gyrase genes gyrA and gyrB [1], and DNA topoisomerase IV genes parC and parE, showed no codon mutations. High-level resistance to tetracyclines in M. hominis and Ureaplasma spp. has been associated with the presence of the tet(M) determinant [3]. This acquired resistance determinant was absent in MYC02. Hence, genomic drug susceptibility prediction predicts susceptibility to macrolides, quinolones, and tetracyclines although phenotypic antimicrobial susceptibility testing was not performed.

The core‑genome SNP phylogeny was inferred using the NASP pipeline[5], leveraging all publicly available M. hominis genomes from the NCBI GenBank database (https://www.ncbi.nlm.nih.gov/datasets/genome/?taxon=2098). SNP differences between MYC02 and other isolates ranged from 5471 to 8074, suggesting considerable genetic divergence and indicating that MYC02 is genetically distinct within the M. hominis population.

Discussion

An expanded multilocus sequence typing (eMLST) scheme, combining the previously reported multilocus sequence typing (MLST) loci (gyrB, tuf, ftsY, uvrA, gap) with a new selected set of putative virulence genes (p120’, vaa, lmp1, lmp3, p60) [2] has been proposed. This scheme allows for the segregation of the M. hominis population into two distinct genetic lineages, which are associated with different pathotypes: infertility-associated (lineage A) and gynaecological infections (lineage B) [2]. The eMLST analysis for the MYC02 isolate using the MLST tool (https://github.com/tseemann/mlst) identified closest matches to eST20 (lineage A), placing the isolate within the infertility-associated pathotype. These findings underscore the genetic heterogeneity of M. hominis and the potential clinical implications of lineage-specific differences.

Conclusion

This case report underscores the clinical significance and diagnostic challenges of Mycoplasma hominis infections in pregnancy. Our case of chorioamnionitis following preterm premature rupture of membranes was confirmed via routine placental cultures, MALDI-TOF MS, and whole-genome sequencing, which revealed no resistance mutations and a notable genetic divergence from other strains as determined by a core-genome SNP phylogeny using the NASP pipeline. Although our isolate was successfully cultured on routine media, the limited availability of specific Mycoplasma culture techniques and PCR likely contributes to the underdiagnosis of urogenital Mollicute infections, leaving their true prevalence and clinical impact uncertain. Moreover, while Mycoplasma infections have been associated with adverse pregnancy outcomes, it remains unclear whether targeted anti-mycoplasma antimicrobial therapy could prevent or reduce such complications.

Ethical approval statement

No written consent has been obtained from the patient, as this case report/series does not contain any patient-identifiable data. According to the local Institutional Review Board (IRB) guidelines, case reports do not require separate ethical approval when patient-identifiable information is not included.

Funding

This work was supported by funding awarded to Jeanette Teo under the National University Health System Seed Fund (NUHSRO/2023/036/RO5 +6/Seed-Mar/01).

CRediT authorship contribution statement

Teo Jeanette: Writing – original draft, Funding acquisition, Data curation. Tan Ker Xin: Methodology, Investigation. Chew Ka: Writing – original draft, Investigation.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data availability

The data that support the findings of this study are openly available in NCBI at https://www.ncbi.nlm.nih.gov/bioproject/PRJNA1160405, reference number PRJNA1160405.