What is the true clinical relevance of Simkania negevensis and other emerging Chlamydiales members?

Abstract

Waddlia chondrophila and Simkania negevensis are emerging Chlamydia-related bacteria. Similar to the pathogenic organisms Chlamydia pneumoniae and Chlamydia trachomatis, these emerging bacteria are implicated in human genital infections and respiratory diseases. We used a screening strategy based on a newly developed S. negevensis–specific quantitative real-time PCR (qPCR) and a pan-Chlamydiales qPCR. We could not detect S. negevensis in 458 respiratory, genitourinary, cardiac and hepatic samples tested. One urethral swab was positive for W. chondrophila. We observed a low prevalence of Chlamydiales in respiratory samples (1/200, 0.5%), which suggests that C. pneumoniae is an uncommon respiratory pathogen. Furthermore, we screened 414 human serum samples from Switzerland, England and Israel and observed a low prevalence (<1%) of exposure to S. negevensis. Conversely, humans were commonly exposed to W. chondrophila, with seroprevalences ranging from 8.6% to 32.5%. S. negevensis is not a clinically relevant pathogen, but further research investigating the role of W. chondrophila is needed.

Waddlia chondrophila and Male Infertility

“…Most studies have targeted female patients, while seroprevalence of W. chondrophila in men has only been investigated on two occasions, until now. In the first study, 13.7% of healthy young Swiss men (66 out of 482) attending military service tested positive [24], while in the second, this was the case for 45% (18 out of 40) of Israeli men [25].…”

Screening of Chlamydia trachomatis and Waddlia chondrophila Antibodies in Women with Tubal Factor Infertility

“…High titers of W. chondrophila antibodies were associated with severe TFI, independent of C. trachomatis titers. Currently, there are only limited studies in which the seroprevalence of W. chondrophila is studied among the general population [22][23][24]. One study by Baud et al investigated the seroprevalence among 482 asymptomatic Swiss men (average age of 20 years) and observed a positive W. chondrophila IgG in 8.3% of the subjects [22].…”

Polish Journal of Veterinary Sciences

“…When analysing the representatives of the Simkaniaceae family in the epidemiological meaning, it must be stated that particularly S. negevensis is a factor pathogenic to humans, as it was isolated from bronchitis in children and adults in Israel (Negev) (Lieberman et al 1997, Kahane et al 1998, Friedman et al 1999, Greenberg et al 2003. Furthermore, among adult Inuit people in Canada (Lieberman et al 2002, Greenberg et al 2003, and among adults in Japan (Yamaguchi et al 2005), in Jordan (Al-Younes and Paldanius 2014), and in European countries (Switzerland, England, Israel) (Vouga et al 2018), high level of anti-Simkania sp. antibodies were found, which points to the presence of such bacteria in these societies.…”