Background review for the ‘2015 European guideline on the management of Chlamydia trachomatis infections’

The history, replication, genetics, characteristics (both biological and physical), and factors involved in the pathogenesis of Mycoplasma genitalium are presented. The latter factors include adhesion, the influence of hormones, motility, possible toxin production, and immunological responses. The preferred site of colonization, together with current detection procedures, mainly by PCR technology, is discussed. The relationships between M. genitalium and various diseases are highlighted. These diseases include acute and chronic nongonococcal urethritis, balanoposthitis, chronic prostatitis, and acute epididymitis in men and urethritis, bacterial vaginosis, vaginitis, cervicitis, pelvic inflammatory disease, and reproductive disease in women. A causative relationship, or otherwise strong association, between several of these diseases and M. genitalium is apparent, and the extent of this, on a subjective basis, is presented; also provided is a comparison between M. genitalium and two other genital tract-orientated mollicutes, namely, Mycoplasma hominis, the first mycoplasma of human origin to be discovered, and Ureaplasma species. Also discussed is the relationship between M. genitalium and infertility and also arthritis in both men and women, as is infection in homosexual and immunodeficient patients. Decreased immunity, as in HIV infections, may enhance mycoplasmal detection and increase disease severity. Finally, aspects of the antimicrobial susceptibility and resistance of M. genitalium, together with the treatment and possible prevention of mycoplasmal disease, are discussed.

The current taxonomic classification of Chlamydia is based on limited phenotypic, morphologic and genetic criteria. This classification does not take into account recent analysis of the ribosomal operon or recently identified obligately intracellular organisms that have a chlamydia-like developmental cycle of replication. Neither does it provide a systematic rationale for identifying new strains. In this study, phylogenetic analyses of the 16S and 23S rRNA genes are presented with corroborating genetic and phenotypic information to show that the order Chlamydiales contains at least four distinct groups at the family level and that within the Chlamydiaceae are two distinct lineages which branch into nine separate clusters. In this report a reclassification of the order Chlamydiales and its current taxa is proposed. This proposal retains currently known strains with > 90% 16S rRNA identity in the family Chlamydiaceae and separates other chlamydia-like organisms that have 80-90% 16S rRNA relatedness to the Chlamydiaceae into new families. Chlamydiae that were previously described as 'Candidatus Parachlamydia acanthamoebae' Amann, Springer, Schönhuber, Ludwig, Schmid, Müller and Michel 1997, become members of Parachlamydiaceae fam. nov., Parachlamydia acanthamoebae gen. nov., sp. now. 'Simkania' strain Z becomes the founding member of Simkaniaceae fam. nov., Simkania negevensis gen. nov., sp. nov. The fourth group, which includes strain WSU 86-1044, was left unnamed. The Chlamydiaceae, which currently has only the genus Chlamydia, is divided into two genera, Chlamydia and Chlamydophila gen. nov. Two new species, Chlamydia muridarum sp. nov. and Chlamydia suis sp. nov., join Chlamydia trachomatis in the emended genus Chlamydia. Chlamydophila gen. nov. assimilates the current species, Chlamydia pecorum, Chlamydia pneumoniae and Chlamydia psittaci, to form Chlamydophila pecorum comb. nov., Chlamydophila pneumoniae comb. nov. and Chlamydophila psittaci comb. nov. Three new Chlamydophila species are derived from Chlamydia psittaci: Chlamydophila abortus gen. nov., sp. nov., Chlamydophila caviae gen. nov., sp. nov. and Chlamydophila felis gen. nov., sp. nov. Emended descriptions for the order Chlamydiales and for the family Chlamydiaceae are provided. These families, genera and species are readily distinguished by analysis of signature sequences in the 16S and 23S ribosomal genes.

The Centers for Disease Control and Prevention developed screening and diagnostic testing guidelines for chlamydia and gonorrhea at urethral, rectal, and pharyngeal sites for men who have sex with men (MSM). However, in most clinical settings, rectal chlamydial testing is not performed for MSM, and primarily sexually transmitted disease (STD) clinics alone perform routine rectal and pharyngeal gonorrhea screening for asymptomatic men. We evaluated the prevalence of rectal, urethral, and pharyngeal chlamydial and gonococcal infections among MSM seen at the municipal STD clinic and the gay men's community health center. We also determined the proportion of asymptomatic rectal infections, described the patterns of single and multiple anatomic sites of infection, and evaluated the proportion of chlamydial infections that would be missed and not treated if MSM were not routinely tested for chlamydia. We tested specimens using previously validated nucleic acid amplification tests (NAATs). The prevalence of infection varied by anatomic site (chlamydia: rectal, 7.9%; urethral, 5.2%; and pharyngeal, 1.4%; for gonorrhea, rectal, 6.9%; urethral, 6.0%; and pharyngeal, 9.2%). Approximately 85% of rectal infections were asymptomatic supporting the need for routine screening. Because 53% of chlamydial infections and 64% of gonococcal infections were at nonurethral sites, these infections would be missed and not treated if only urethral screening was performed. In addition, >70% of chlamydial infections would be missed and not treated if MSM were tested only for gonorrhea. Because these infections enhance both HIV transmission and susceptibility, clinical settings serving MSM should evaluate the prevalence of chlamydial and gonococcal infections by anatomic site using validated NAATs.