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The notion that Mycoplasma hominis is an unimportant micro-organism in the genital tract is not without merit, but certain facts suggest that the topic should be reconsidered.
Since M. hominis was isolated about 73 years ago, there have been mixed observations regarding pathogenicity. Nasopharyngeal inoculation of men caused exudative pharyngitis and cervical lymphadenopathy1 and those who had high titres of preinoculation antibody were the least likely to develop disease.1 Subsequently, M. hominis was found to cause arthritis in patients with hypogammaglobulinaemia,2 and occasionally to be associated with postpregnancy arthritis, but not with STI-related reactive arthritis.3 Detection is very common in bacterial vaginosis, but causality has never been proved. Although early studies suggested association with salpingitis,4 a significant role in pelvic inflammatory disease is unclear.5
Multiple studies have failed to identify M. hominis as a pathogen in male non-gonococcal urethritis (NGU). However, detailed analyses of the strains involved have never accompanied such studies. Genetic heterogeneity could be a factor in pathogenicity. Strain PG21 appears to be closely related to, but not identical with, strains DC63 and V2785 in gel diffusion tests.6 Furthermore, Lin7 noted distinct differences between seven strains in agglutination tests, and in growth-inhibition tests antiserum has not inhibited all strains equally (Taylor-Robinson, unpublished data). Manchee and Taylor-Robinson8 were first to note that various strains were able to attach to eukaryotic cells, and penetration was also seen,9 possible important first steps in pathogenesis. Others10 similarly observed phenotypic and genotypic differences between strains and differences in their attachment abilities.
Detailed research is required to determine the role of M. hominis load, phenotype and genotype not only in male NGU but also in female genital tract disease. This is a challenge given that the necessary physician–microbiologist expertise, interest and resources have dwindled. In the meantime, current guidance for routine diagnostic practice should be observed.
Handling editor Anna Maria Geretti
Funding This study was funded by Medical Research Council.
Competing interests None declared.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; internally peer reviewed.
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