670 - Rapid, Non-invasive Detection of Invasive Mycoplasma hominis Infection using the Karius Test, A Next-Generation Sequencing Test for Microbial Cell-free DNA in Plasma

Background: Mycoplasma hominis is typically associated with genital infections in women and is a rare cause of musculoskeletal infections often in immunocompromised hosts. Diagnosis of invasive Mycoplasma hominis infections are difficult due to challenges in culturing these organisms. Molecular diagnostics require an index of suspicion which may not be present at the time of tissue sampling. Accurate, rapid diagnosis of Mycoplasma hominis infections are important for antibiotic management.

Methods: Two cases of invasive Mycoplasma hominis infections are presented in which the Karius test (KT) was used to make the diagnosis. The KT is a CLIA certified/CAP-accredited next-generation sequencing (NGS) plasma test that detects microbial cell-free DNA (mcfDNA). After mcfDNA is extracted and NGS performed, human reads are removed and remaining sequences are aligned to a curated database of > 1400 organisms. Organisms present above a statistical threshold are reported. Case review was performed for clinical correlation.

Results: A young woman with lupus nephritis status post renal transplant developed persistent fever with progressive multifocal culture-negative osteoarticular infection despite empiric ceftriaxone. An adolescent female presented with an ascending pelvic infection progressing to purulent polymicrobial peritonitis (see table) requiring surgical debridement and cefipime, metronidazole and micafungin therapy; her course was complicated by progressive peritonitis/abscesses. Karius testing detected high-levels of Mycoplasma hominis mcfDNA in both cases – at 3251 molecules/microliter (MPM) in the first case and 3914 MPM in the second case. The normal range of Mycoplasma hominis mcfDNA in a cohort of 684 normal adults is 0 MPM. The patients rapidly improved with atypical coverage with doxycycline and levofloxaxin.Clinical findings in 2 patients with M. hominis infection detected by the Karius Test


Conclusion: Open-ended, plasma-based NGS for mcfDNA provides a rapid, non-invasive method to diagnose invasive Mycoplasma hominis infection. This case series highlights the potential to diagnose infections caused by fastidious pathogens to better inform antimicrobial therapy and achieve favorable outcomes.