Identification of sacrococcygeal and pelvic abscesses infected with invasive Mycoplasma hominis by MALDI-TOF MS.

backgroundMycoplasma hominis is the smallest prokaryotic microorganism with no cell wall, high pleomorphism, and slower reproduction than bacteria. It is difficult for clinical technicians to find M. hominis through the negative Gram staining of specimens. Therefore, it is likely to miss detection in routine clinical smear etiological examination. M. hominis is generally considered to be a common colonizing bacterium in urogenital tract with low pathogenicity, and it is usually difficult to invade submucosal tissue and enter the bloodstream.

methodsThe abscesses of the patient were examined histopathologically, and the pus in the abscesses was extracted for etiological examination. MALDI-TOF MS was used to identify and confirmed the pathogens in the specimens. The commercial Mycoplasma isolation, culture, and drug sensitivity kit was used to determine antibiotic susceptibility.

resultsNo pathogens were found after pathological and smear microscopic examination of the puncture fluid from the sacrococcygeal and pelvic abscesses. Until 48 h later, small, translucent, and gray-white colonies were observed in the blood plate culture results. The laboratory physician ultimately determined that the pathogen was M. hominis by MALDI-TOF MS.

conclusionWe report a case of extra-urogenital cystic abscesses infected by M. hominis, in order to improve clinicians' comprehensive understanding of the pathogenicity of Mycoplasma. In addition, the clinical laboratory technician should pay attention to the role of Wright-Giemsa staining of puncture fluid smear in the preliminary detection and the application of MALDI-TOF MS in identification of uncommon pathogenic microorganisms.