Severe pneumonia due to Parachlamydia acanthamoebae following intranasal inoculation: a mice model

Abstract

Parachlamydia acanthamoebae is an obligate intracellular bacterium naturally infecting free-living amoebae. The role of this bacterium as an agent of pneumonia is suggested by sero-epidemiological studies and molecular surveys. Furthermore, P. acanthamoebae may escape macrophages microbicidal effectors. Recently, we demonstrated that intratracheal inoculation of P. acanthamoebae induced pneumonia in 100% of infected mice. However, the intratracheal route of infection is not the natural way of infection and we therefore developed an intranasal murine model. Mice inoculated with P. acanthamoebae by intranasal inoculation lost 18% of their weight up to 8 days post-inoculation. All mice presented histological signs of pneumonia at day 2, 4, 7, and 10 post-inoculation, whereas no control mice harboured signs of pneumonia. A 5-fold increase in bacterial load was observed from day 0 to day 4 post-inoculation. Lungs of inoculated mice were positive by Parachlamydia-specific immunohistochemistry 4 days post-inoculation, and P. acanthamoebae were localized within macrophages. Thus, we demonstrated that P. acanthamoebae induce a severe pneumonia in mice. This animal model (i) further supports the role of P. acanthamoebae as an agent of pneumonia, confirming the third Koch postulate, and (ii) identified alveolar macrophages as one of the initial cells where P. acanthamoebae is localized following infection.

A Review on Chlamydial Diseases in Animals: Still a Challenge for Pathologists?

“…94 During an intranasal and intratracheal experimental infection mouse model, P. acanthamoebae induced severe interstitial pneumonia which was purulent in the early phase (2-4 days after infection, dpi) and mononuclear at 7-21 dpi. 30,118 Transmission modes of CRB are unknown but aquatic sources might play a role (reviewed in Wheelhouse and Longbottom 187 ). A zoonotic potential has to be considered as CRB have been indirectly linked to recurrent pregnancy failure and miscarriage in women as well as pneumonia and bronchiolitis in children and patients with community-acquired pneumonia.…”

“…94 During an intranasal and intratracheal experimental infection mouse model, P. acanthamoebae induced severe interstitial pneumonia which was purulent in the early phase (2–4 days after infection, dpi) and mononuclear at 7–21 dpi. 30,118…”

Parachlamydia acanthamoebae Detected during a Pneumonia Outbreak in Southeastern Finland, in 2017–2018

“…Parachlamydia acanthamoebae is the most studied member of the chlamydia-related bacteria, including several studies presenting evidence supporting its role as a CAP causing pathogen [4,5,30,31]. In vitro, Parachlamydia is indeed able to enter and grow in cells present in respiratory tract, macrophages [32] and pneumocytes [33].…”

“…The role of Parachlamydia acanthamoebae as an agent of pneumonia is most studied and many of the modified Koch’s postulates are fulfilled. For instance, the pathogenicity is suggested by sero-epidemiological and molecular studies as well as by an experimental pneumonia model including a treatment trial [4,5]. Waddlia chondrophila is mainly associated with tubal factor infertility [6] and adverse pregnancy outcome [7], but also with lower respiratory tract infections [4,8,9].…”

An update on the detection methods of Parachlamydia acanthamoebae, an atypical agent of pneumonia

“…Additionally, serology permits the retrospective confirmation of an infection as it demonstrates differences between samples from the acute and convalescent phases effectively besides having the capability to identify chronic infections (Maggi et al, 2014;Nilsson et al, 2005). There appears to be an emphasis on employing immunofluorescence for the detection of P. acanthamoebae with direct and indirect immunofluorescence having rather similar usage rates (Greub, Boyadjiev, et al, 2003;Hayashi et al, 2012;Marrie et al, 2001;Pilloux et al, 2015). Similar to IHC, immunofluorescence allows visualization of P. acanthamoebae in cells or tissues which permits it to be ascribed as an etiological agent for the said disease.…”